Archive

2010, Volume 17 Issue 2
15 March 2010 Previous Issue    Next Issue
---
Article


For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Article

Select

Banded iron formation and related great oxidation event. DIAO Zhen-Hua 2010, 17(2): 1-12.  Abstract ( 3206 )   PDF (2062KB) ( 4555 )    Great Oxidation Event (GOE) is the appearance and continuous increase of oxygen in atmosphere about 2.4 Ga ago. The model for GOE generation and evolution can be summarized as two types up to the end of twentieth century: the first one is socalled C-W-K-O model which postulates an anoxic atmosphere prior to 2.2 Ga with p(O2) levels between 10-13 and 0.1％ of present atmospheric level (PAL), and a dramatic rise of p(O2) to >15％ PAL between 2.2-1.9 Ga; the second one is D-K-O model which postulates an essentially constant atmospheric p(O2) level (probably within ±50％ of PAL) since 4.0 Ga. The Archean Biosphere Drilling Project (ABDP) has carried out in the beginning of the 21 century. The drilling targets were ArcheanProterozoic formations, such as shale and banded iron formation (BIF) etc. The investigations on microorganism, S and C isotope fractionation, REE and changes of transition metals Ni, Fe, Mo contents have produced many new results for building new and different models of the timing and generation mechanism of GOE. The appearance of free O2 in the atmosphere is at least advanced to 2.5 Ga. The BIF especially the REEFe formation are widely developed in China. Preliminary researches on the REE geochemistry of BIF have shown that the REE contents and fractionation (La/Yb), particular the enrichment or depletion of Eu have had systematic change with time. We suggest that we should carry out systematic geological and geochemical studies, in particular the REE geochemistry studies, on the BIF, which may make important contributions to the GOE study and certainly to the investigations of the iron ore deposit formation and distribution in our country. Related Articles | Metrics

Select

Some scientific questions on the intracontinental metallogeny in the South China continent. HU Rui-Zhong, MAO Jing-Wen, FAN Wei-Ming, HUA Ren-Min, BI Xian-Wu, ZHONG Hong, SONG Xie-Tan, DAO Yan 2010, 17(2): 13-26.  Abstract ( 4771 )   PDF (2040KB) ( 6334 )    The South China continent including the Yangtze Block and the Cathaysia Block is an uncommon worldclass polymetallic metallogenic province with great oreforming potential. The formation and evolution of the South China continent had undergone specific intracontinental dynamic processes, in which the Late Permian plumerelated metallogenic system, the Mesozoic huge lowtemperature metallogenic system and the metallogenic system of the Mesozoic great granite province are quite distinctive in the world. Thus, the South China continent becomes an ideal international base for studying the intracontinental mineralization. The studies, in various levels, of how the continental dynamic processes over different geological time control the mineralization in the South China continent have been carried out and have had important achievements. On the basis of these studies, this paper presents the major scientific questions for further research on the three metallogenic systems. Related Articles | Metrics

Select

On epizonogenism and genetic classification of hydrothermal deposits. CHEN Yan-Jing 2010, 17(2): 27-34.  Abstract ( 6795 )   PDF (1221KB) ( 17497 )   Abstract:  This paper, through listing the genetic type names of hydrothermal gold deposits presented in literatures, reveals that the existing genetic classifications of hydrothermal deposits are scientifically illogical, confusing and abusive, without satisfactory connection to logics in other geoscience disciplines. This greatly hinders the ore geological training, research and exploration targeting, and is resulted from a conceptual gap of the geological processes occurred at depths less than 10 km and temperatures of 50300 ℃. Hence we propose a concept of epizonogenism to describe the geological processes occurred at depths of <10 km and temperatures of 50300 ℃. In correspondence, hydrothermal deposits are classified into three endmembers, namely epizonogenic, metamorphic and magmatic. It is confirmed that the epizonogenic fluids are characterized by lowsalinity and CO2poor, the metamorphic fluids by lowsalinity and highcontent of CO2rich, and the magmatic fluids by highsalinity and variable content of CO2. The magmatic hydrothermal systems contain multiple daughtercrystalsbearing and CO2rich highsalinity fluid inclusions; the metamorphic deposits contain lowsalinity CO2rich fluid inclusions; and the epizonogenic hydrothermal systems contain neither daughtercrystalbearing nor CO2rich/bearing fluid inclusions, but are populated by aqueous fluid inclusions. Related Articles | Metrics

Select

Learning and practicing  the theory of Reworked Metallization—An example from the sandstonehosted copper deposits  in Central Yunan with special reference  to the defining of  upper and lower limits of the Reworked Metallization. DAN Chong-Yang, HU Yu-Zhao, TUN Feng, HE Meng-Qi, CHEN Hao-Shou, WANG Hua-Kun, HAN Run-Sheng 2010, 17(2): 35-44.  Abstract ( 2195 )   PDF (1669KB) ( 2891 )   The concept of “Reworked Metallization” is a new theory proposed by Prof. Tu Guangzhi. This theory has its basic arguments and distinctive characteristics as follows: the extensiveness of metallogenic material; the uniqueness of oreforming fluids; the activity  of the metallogenic elements; the endogenic characteristic of the reworked metallization; the  leading role played by faulting; the diversity of the host rocks; the widespreading of the reworked deposits. Their metallization is unique and has a proper position in the fourfold division of ore deposits. DayaoMouding type of sandstonehosted copper deposits in Central Yunnan are of typical sedimentarydiageneticanadiageneticreworked metallogeneses. Their main arguments are as follows: rifting metallogenesis setting; source bed (K,J) and source rock (Yuanmou paleocontinent); the ore bodies are controlled by stratigraphy, lithofacies and lithology. Their characteristics and their occurrence are closely related to coal series which provides organic matter and salt bed  that in turn provides halogen for the ore. The shape and occurrence of ore bodies, the texture and structure of ores, the behavior  of oreforming fluids and the source of water and the type of organic matter  and its effect  are distinct during different metallogenetic stages. To interpret and determine the limits of reworked metallization in terms  of the concepts of petrogeny, the upper limit (beginning) is set  afteranadiagenesis and the lower limit (ending) is at the end of quasimetamorphism. Related Articles | Metrics

Select

Geochemistry of hydrothermal mineralization: Taking gold deposit as an example. SHU Yong-Feng 2010, 17(2): 45-52.  Abstract ( 2192 )   PDF (869KB) ( 3108 )   Hydrothermal alteration, geochemistry of gold in hydrothermal fluid, concentration form and precipitation mechanism of gold and its forms in sulfide are summarized in this paper. Hydrothermal alteration is the reaction between fluid and host rocks. Mineral assemblages formed during alteration reflect the geochemical feature of oreforming fluids. Gold is always transported as Au-Cl and Au-S complexes in fluids. The change of physicochemical conditions such as temperature, pressure, oxygen fugacity and sulfur fugacity is the effective mechanism for gold precipitation. In fluid with high temperature and pressure, gold tends to concentrate in vapor phase. Au-As and Au-Sb associations are common in gold deposit. In hydrothermal with low sulfur fugacity, native antimony/arsenicnative gold assemblage may precipitate. Gold is probably hosted in sulfide as inclusion or solid solution after precipitated from fluid. Related Articles | Metrics

Select

The multiperiodic superimposed porphyry copper mineralization in Central Asian Tectonic Region: A case study of geology, geochemistry and chronology of Halasu copper deposit, Southeastern Altai, China. XUE Chun-Ji, DIAO Zhan-Feng, TUN Gan-Guo, DONG Lian-Hui, FENG Jing, ZHANG Qiao-Chong, ZHOU Gang, CHE Guo-Xiang, GAO Jing-Gang 2010, 17(2): 53-82.  Abstract ( 4708 )   PDF (5019KB) ( 4301 )    The Halasu copper deposit is recently discovered in Qinghe, Xinjiang, and proved to be a largescale copper prospect by the exploration in progress. It is located at the southeastern Altai and near the Ertix tectonic deformation zone. The region had undergone the Middle Paleozoic ocean plate subduction, the Later Paleozoic continental collision and the successive intraplate activation  processes. That which process was related to the copper ore mineralization has  caused much attention, and there are debates on the metallogenesis of the ore, such as,  porphyry copper type, hydrothermal copper veintype and volcanic related copper deposit.  The Middle Devonian basic volcanic rock (including picrites) and copperbearing altered porphyry including granodiorite porphyry, porphyritic granite, quartz monzonite porphyry and quartz diorite porphyry of different periods crop out mainly in Halasu copper ore district. The porphyrys SiO2 content is from 57.24% to 65.45%; the granodiorite porphyrys δ18OVSMOW  value is from 7.9‰ to 8.6‰, its εNd(t)  is from 7.3 to 8.5 (near the value of MORB), and (87Sr/86Sr)t is from 0.70383 to 0.70410 (near the original mantle value); these indicate a mantle or lower crust magma sources. The copperbearing alteration porphyry is whole mineralized (Cu 02%), the orebody (Cu over 0.3%) is lenticular and irregularly dendritic veinshaped and its occurrence is similar to that of  the porphyry, and over  95%  of  the orebodies are located within  the porphyry. The wallrock alteration  developed in a sequence of the zones of Kfeldsparbiotite, biotitechlorite, to propylite from the orebody to the porphyry and then to basic volcanic wallrock, and the later veinlets of  linear Kfeldsparization  overprinted on the earlier pervasive Ksilicate alteration. There is no secondary sulfide enrichment, and the primary copper ores are of two natural types : the veinletdisseminated and the veinoverprinted, the former is characterized by the typical metallic mineral association of pyritechalcopyritemolybdenite, and the latter is overprinted on the former by quartzpyritechalcopyrite veins. As compared with the former, the latter has the higher grade (Cu to 2.21% and Au to 0.83 g/t), and lower total amount of the trace and rare  earth elements with more gentle  REE pattern and more evident positive Eu anomaly and flatter spider diagram of the trace elements. The basic volcanic eruption, the mantlesource magma intrusion and the superposition of multiphase  metallization   are the key factors for the Halasu copper metallization. The porphyry copper mineralizations of early period  were overprinted by the later period of structuralhydrothermal metallization. The Sisotopic compositions of associated pyritechalcopyrite in the veinletdisseminated type of copper ores indicate the 420560 ℃ of porphyry copper mineralization temperature. The copper ore sulfide δ34SVCDT is mainly from -1‰ to -4‰, and the ore sulphur was from the mantle source porphyry intrusion (with minor mixing of  reduced sulphur  from the sulfates in surrounding strata ). The pyrite in the copper ores shows that 206Pb/204Pb is from 18.052 to 18.461, 207Pb/204Pb from 15.501 to 15.606 and 208Pb/204Pb from 37.813 to 39.335, and these are close to that of CuNi sulfides in Kalatongke ultrabasic intrusion. The metal was mainly from the mantle source porphyry intrusion. The parent hydrothermal solution (δ18OVSMOW=6.4‰10.2‰，δDVSMOW=-89‰-80‰) from which crystallized the copperbearing sulfide quartz vein in the veinoverprinted type of copper ores shows the O and Hisotopic compositions of magma source water. The isotopic chronology research of the porphyry intrusion, the copper ore and the alteration suggest that (1) the UPb concordant ages of (381.6±2.5) Ma and (371.8±96) Ma by zircons in copperbearing altered  porphritic granite and granodiorite porphyry, respectively, and the ReOs isochron age of (376.9±2.2) Ma by molybdenites in the veinletdisseminated copper ores are all the porphyry intrusion and porphyry copper metallization records of the oceanic platecontinent subduction period; that (2) the UPb concordant age of (265.6±3.7) Ma by zircon in copperbearing altered quartz monzonite porphyry and the ArAr plateau age of (269.2±3.2) Ma by Kfeldspar in the veinoverprinted type of copper ores are porphyry copper metallization and alteration records of the continentcontinent collision period; that (3) the UPb concordant age of (215.8±4.6) Ma by zircon in the copperbearing altered quartz diorite porphyry and ArAr plateau age of (198.2±2.3)(206.4±2.7) Ma by Kfeldspar in veinoverprinted type of copper ores are the copper mineralization and related alteration records of intraplate  activization period. The Halasu copper metallization is characterized by multiphase  tectonicmagmatichydrothermaloverprinting. This  study provides some new facts for the understanding of the superposition porphyry copper metallization in the tectonic domain of Central Asia. Related Articles | Metrics

Select

The coupling relationship between metallization and hydrocarbon accumulation in sedimentary basins. GU Xue-Xiang, ZHANG Yong-Mei, LI Bao-Hua, XUE Chun-Ji, DONG Shu-Xi, FU Chao-Hong, CHENG Wen-Bin, LIU Li, TUN Cheng-Bin 2010, 17(2): 83-105.  Abstract ( 2787 )   PDF (4944KB) ( 1367 )    The metallic ore deposits closely associated with hydrocarbon reservoirs in sedimentary basins mainly include the Mississippi Valleytype (MVT) PbZn deposits, the sandstoneand shalehosted CuU deposits, the sulfide deposits in black shales, and the sedimentary rockhosted AuSbAsHgTl deposits. The intimate association suggests a genetic linkage between metallization and hydrocarbon accumulation. In many MVT PbZn deposits and sandstone/shalehosted Cu deposits, crude oil and its derivatives predate metallization and may have provided reduced sulfur directly to the ore system or acted as reductant facilitating the reduction of sulfate. Under other circumstances, metals in some lowtemperature hydrothermal ore deposits, especially in sedimentary rockhosted Au, As, Hg, Sb and Tl deposits, may originate, transport and precipitate along with hydrocarbons, suggesting simultaneous metallization and hydrocarbon accumulation. The metallic ore deposits having different coupling relationships with hydrocarbons show different characteristics. The basinal fluids associated with metallization and/or reservoir formation include hydrocarbonrich organic fluids, metalrich aqueous fluids, and both hydrocarbon and metalrich organic oreforming fluids. Metallization, hydrocarbon accumulation and their coupling relationship in a sedimentary basin may be governed by the evolution of these fluids. The intimate association between ore deposits and hydrocarbon reservoirs and the similarity in process and mechanism for metallization and reservoir formation make it possible to carry out the coordinative exploration and comprehensive forecast of both metal and oilgas resources in sedimentary basins. Related Articles | Metrics

Select

Characteristics and origin of Fe-Ti-P oxide deposits associated with Proterozoic massiftype anorthosite. DIAO Ta-Beng, CHEN Wei, LEI Bing 2010, 17(2): 106-117.  Abstract ( 2035 )   PDF (2520KB) ( 966 )   Massiftype anorthosite is referred to igneous rocks consisting of over 90％ plagioclase. The massiftype anorthosite bodies formed in the Proterozoic ranging from 2.1 Ga to 0.9 Ga, and commonly host abundant FeTiP oxide ores. FeTiP ore bodies occurred as conformable layers or irregular shapes as lenses, sheets or veins. The ores usually are of massive and disseminated types; the former type contains more than 70％ ore minerals, and the latter one contains 20% to 70％. Ore minerals from some deposits are mainly titanomagnetite with minor ilmenite, whereas the others are mainly hemoilmenite with minor magnetite. Some of ores contain abundant amounts of apatite, which forms nelsonite containing only FeTi oxides and apatite. These FeTiP ores have been commonly interpreted as forming from a FeTirich magma which usually represents residual magma after extensive crystallization of plagioclase in a deep chamber. However, it is controversial on the oreformation mechanisms. They were assumed to have crystallized from immiscible FeTiP liquids separated from silicate magma or represent cumulate rocks that directly crystallized from silicate magmas. The Damiao FeTiP oxide deposit is the unique deposit hosted in massiftype anorthosite in China. Its ore bodies commonly occur as irregular lenses, veins or pods with sharp contact with anorthosite, and consist of different zones of FeTiP ores upwards instead of obvious igneous layering. Based on detailed petrography, mineral proportions, mineral compositions and wholerock geochemistry, we conclude that various ores at Damiao are mixtures of cumulus mineral and trapped liquids, and that they formed from a ferrodioritic magma by fractional crystallization and accumulation. The discordant occurrence of various ores may be related to the dynamic crystallization process and/or subsolidus remobilization. Related Articles | Metrics

Select

Emplacement sequence in the Jinchuan sulfide orebearing ultramafic intrusion, western China. SU Chang-Guo, SHANG Zhong-Li, ZHOU Dai 2010, 17(2): 118-126.  Abstract ( 1913 )   PDF (1914KB) ( 1073 )   The Jinchuan ultramafic intrusion in western China hosts the third largest magmatic CuNi deposit in the world, but the emplacement history of the magma and sulfide liquid in the intrusion remains poorly understood. Based on the lithological structure, crosscutting relationships and compositional variations in the intrusion, we propose a fivestage emplacement model: (1) formation of sulfidepoor ultramafic lithology by injection of an olivinerich magma; (2) formation of disseminated sulfide zones by injection of olivinerich magma containing small amounts of suspended sulfide droplets; (3) formation of nettextured sulfide ore zones by injection of sulfide olivinerich magma; (4) formation of massive sulfides zones ore body by injection of sulfide liquid; and (5) formation of CuPtPdrich sulfide veins by injection of fractionated sulfide liquids derived by fractional crystallization from nearby sulfide zones and emplaced into fractures in the intrusion and footwall rocks. Ni, Cu, Pt, Pd, Rh, Ir, Ru, and Co correlate positively with S indicating that they were hosted primarily in sulfides. PtPd enrichment zones are the relic liquid of monosulfide solid solution segregation,and massive ore may represent the accumulation of monosulfide solid solution. The magma conduit of Jinchuan CuNi (PGE) sulfide deposit belongs to dike magma conduit. Related Articles | Metrics

Select

Geological and geochemical characteristics of laterite nickel deposit and ore genesis—A case study of Kolonodale deposit in Indonesia Sulawesi, FU Wei, ZHOU Yong-Zhang, CHEN Yuan-Rong, HU Yun-Hu, CHEN Na-Chun, NIU Hu-Jie, ZHANG Zhi-Wei, LI Xiao-Long 2010, 17(2): 127-139.  Abstract ( 2403 )   PDF (6309KB) ( 3271 )    Laterite nickel deposit is a hotspot of global nickel resource exploration and development, and it is also a key target of foreign mineral resource exploration for our country. The Kolonodale deposit located in Sulawesi Island in Indonesia is a typical deposit in SE Asian laterite nickel deposit belt. The deposit occurred in laterite weathering profile of ultramafic rocks. The orebearing profile can be divided into four vertical layers: the red ferric oxide layer, the yellow clay layer, the sage green ore layer and the protolith. The laterite ore occurred in the upper part of the regolith profile. The major Nibearing minerals are ferric oxyhydroxides. The silicate ore occurred in the middle and lower part of the regolith profile, forming in cracks and voids of saprolite and protolith, dominated by nepouite, willemseite and other hydrated MgNi silicates. The geochemical data show that the differentiation of elements along the profile is obvious, especially the high enrichment of Ni in the deeper layer. The migration of elements in lateritization was affected by superficial environment and geochemical activities. Fe, Al, Ti, and Cr represent the residual elements, Si and Mg belong to filtering elements and Mn, Ca, Co, and Ni are classified to the secondary rich elements. By comparison with global typical laterite nickel deposits, the Kolonodale is determined to be of the insitu silicate type. It is formed by coupling many geological and geographical factors, including the geochemical source from ultramafic rocks, the weathering force affected by rain forest climate, the filtering and precipitation channels provided by structural activities, the ore deposition space offered by good relief, and the time insurance from stable tectonic environment. This study indicates that the oreforming process of the Kolonodale deposit can be divided into three stages: The sparolite stage, the laterite stage and the secondary enrichment stage. Related Articles | Metrics

Select

Re-Os age of  molybdenite from  the Majiawa Au-Mo deposit of quartz vein type  in the north margin of the Xiaoqinling gold area and its implication for metallogeny. WANG Xi-Tian, XIE Hui-Shou, XIE An-Wang, LI Yong-Ge, SHUAI Yun, ZHANG Chang-Jing, DAI Jun-Chi 2010, 17(2): 140-145.  Abstract ( 3334 )   PDF (1081KB) ( 1667 )   The Majiawa AuMo deposit discovered in recent years is located in the north margin of the Xiaoqinling gold area. The orebodies, the AuMobearing quartz veins, are controlled by eastwesttrending brittleductile fault belts. Precise ReOs dating of molybdenite from the Majiawa AuMo deposit has been carried out in this study, and the results show that the ReOs model ages range from 2325 Ma to 2684 Ma with a ReOs isochron age of (231±11) Ma, indicating the molybdenum mineralization occurred in the Triassic. The rhenium contents of molybdenite samples range from 0.474×10-6  to 0.791×10-6, and the initial 187Os/188Os is of 2.4±6.4, which indicate that oreforming materials were derived from the crust. The Majiawa quartz vein type of AuMo deposit was a product of tectonicfluid metallogenic event in the regional extensional regime. It is a new prospective to explore the Indosinian and Yanshanian quartz vein type of AuMo and Mo deposits within brittleductile fault belts developed in Archean basement at the south margin of the North China plate. Related Articles | Metrics

Select

Quaternary zircon geochronology by secondary ion mass spectrometry: A case study of the Chinkuashi dacite from northeastern Taiwan. GAO Yu-Ya, LI Xian-Hua, LI Qiu-Li, ZHONG Sun-Lin- 2010, 17(2): 146-155.  Abstract ( 2578 )   PDF (1485KB) ( 2848 )   Precise age determination of geological events throughout the Quaternary period is fundamental for Quaternary studies and paramount for understanding the Earths evolution. Large radius secondary ion mass spectrometry (SIMS) has increasingly been used in Quaternary geochronology due to its highresolution, highprecision, highefficiency, and nondestructive nature. When applied to UPb zircon geochronology the micrometerscale spatial resolution and high mass resolving power (MRP) of SIMS make it possible to extract complex geologic information preserved within micronsized minerals that would otherwise be obscured or overlooked using other methods. In this paper, we introduce the principles, analytical techniques and correction methods of SIMS insitu UPb dating for Quaternary zircons, and report a SIMS UPb zircon age of (1166±0020) Ma for the Quaternary Chinkuashi dacite from northeastern Taiwan. Related Articles | Metrics

Select

40Ar/39Ar laser probe dating and discussion on metallogenic epoch of epithermal AuCu deposit in Yanbian area of Jilin. DIAO Hu-Jun, SUN Jing-Gui, WANG Qing-Hai, MEN Lan-Jing, LI Yi-Xin, GUO Jia, CUI Pei-Long 2010, 17(2): 156-169.  Abstract ( 2195 )   PDF (1941KB) ( 933 )   延边地区是中国东北部陆缘浅成热液金铜矿床发育的地区之一,广泛发育着浅成热液金矿床、中温热液金(铜)矿床和中深成中高温热液富金铜矿床(类斑岩型);富金铜矿床的成矿时代发生在105～102 Ma,为了进一步确定浅成热液金矿床与中深成中高温热液富金铜矿床的成矿动力学背景,采用流体包裹体的40Ar/39Ar激光探针定年法,对该区典型浅成热液金矿床进行了精细的年代学测定,获得刺猬沟金矿床、五星山金矿床和杜荒岭金矿床的脉石矿物石英流体包裹体的40Ar/39Ar等时线年龄分别为(141±7) Ma、(123±7) Ma和(107±6) Ma,其中刺猬沟金矿床((141±7) Ma)和五星山金矿床((123±7) Ma)的脉石矿物石英流体包裹体含有过剩放射性成因40Ar,而杜荒岭金矿床((107±6) Ma)的脉石矿物石英流体包裹体几乎不含或含极少量过剩放射性成因40Ar。结合最新获得的相关地质体的精细年代学成果,认定该区浅成热液金矿床成矿作用均发生在早白垩世晚期,或发生在早白垩世晚期火山喷发、浅成岩浆就位之后,其形成环境与富金铜矿床一致,为古太平洋板块向亚洲大陆正北向俯冲转入IzanagiFarallon 板块西向俯冲的构造转换期。 Related Articles | Metrics

Select

Rockforming and oreforming ages of the Baizhangyan tungstenmolybdenum ore deposit in Qingyang, Anhui Province and their geological significance. QIN Yan, WANG De-Gong, LI Yan-He, WANG Ke-You, TUN Li-Ban, MEI Yu-Ping 2010, 17(2): 170-177.  Abstract ( 2252 )   PDF (2150KB) ( 896 )   Baizhangyan tungstenmolybdenum ore deposit is a newly developed deposit which was found on the base of a small exposure of mineralization occurrence. With highly precise dating of the ages of the rockforming and oreforming, the authors obtained a SHRIMP UPb zircon age of (130±15) Ma（n=14，MSWD=069）for finegrained granite and ReOs model ages of (133.5±1.9)(135.6±2.0) Ma and isochron age of (136.3±2.6) Ma（n=5，MSWD=0.64）. According to the ages above, the authors concluded that the deposit was formed in the Early Cretaceous; that it was the result of intrusions of the granite which was of crustsource remelting type. The oreforming age is similar to the rockforming age of the granite rock body that was important to the deposit. Related Articles | Metrics

Select

Re-discussion on the metallogenic age of Zhulazaga gold deposit in Alashan Area, Inner Mongolia: Evidence from zircon U-Pb SHRIMP age. LI Dun-Jian, DI Yu-Sheng, YANG Yong-Jiang, WANG Pan-Bin, LI Cheng-Dong, CUI Lai-Wang, ZHOU Gong-Yang, LIU Xiao-Yang, LIU Xiao-Xue, LI Sheng 2010, 17(2): 178-184.  Abstract ( 2579 )   PDF (1265KB) ( 1211 )   Zhulazaga gold deposit is a super large strataboundreconstructive gold  deposit that has been found in recent years in Alashan area, Inner Mongolia. The gold deposit occurs in Mesoproterozoic strata and has great ore prospecting potential; so many people are interested in it. The host rocks mainly are calcareous siltstone and silty slate. Single zircon UPb and quartz 40Ar/39Ar methods are applied to determining the UPb ages of metallogenic periods graniteporphyry and postmetallogenic periods dioriteporphyrite, and the 40Ar/39Ar age of Aubearing quartzsulfide ore body in 2006. The measurements on the zircons showed (304±5) Ma from the metallogenic periods graniteporphyry and (2586±57) Ma from the postmetallogenic periods dioriteporphyrite. The measurement on the quartz from the Aubearing quartzsulfide ore body showed (2823±0.9) Ma. Zircon SHRIMP UPb dating of graniteporphyry and dioriteporphyrite in this study showed that the metallogenic periods graniteporphyry has an emplacement age of (280±6) Ma,and the postmetallogenic periods dioriteporphyrite has an emplacement age of (279.7±5.2) Ma. The time difference between the ages of graniteporphyry and dioriteporphyrite is only 0.3 Ma,thus providing a precise metallogenic age of Zhulazaga gold deposit close to 280 Ma(279.7280 Ma). Related Articles | Metrics

Select

A primary study of the geological characteristics and the zircon UPb age of the Gangjiang porphyry coppermolybdenum deposit in Nimu, Tibet. LENG Cheng-Biao, ZHANG Xin-Chun, ZHOU Wei-De 2010, 17(2): 185-197.  Abstract ( 4267 )   PDF (2936KB) ( 4426 )   Gangjiang coppermolybdenum deposit is located in the Nimu ore field in the middle section of the Gangdese porphyry copper belt. It is a typical porphyrytype deposit discovered in recent years, with more than half million tons of contained copper and molybdenum resources. The Gangjiang complex is composed of biotite quartz monzonite, quartz monzonite porphyry, rhyodacite and dacite. There are many types of hydrothermal alteration including patassic, silicific, phyllic, propylitic, chloritic and argillic alterations. There are obvious potassic and phyllic alteration zones from the central to the outward part of the complex. The copper and molybdenum mineralization occurs mainly in the overlapped part of the potassic and phyllic alteration zones. The supergene oxidation enrichment zone is developed in the top part of the ore bodies. In this paper, the zircon UPb dating method by secondary ion microprobe mass spectrometer (SIMS) is applied to study the intrusion ages of the main orebearing porphyries. The zircon UPb dating ages of the biotite quartz monzonite and rhyodacite are (14.73±0.13) Ma (MSWD=1.3, N=16), and (12.01±0.29) Ma (MSWD=2.3, N=8), respectively. They are in accordance with the ages of orebearing porphyry from other porphyry coppermolybdenum deposits in the Nimu ore field, so the Gangjiang porphyry coppermolybdenum deposit was formed in the extensional tectonic setting posterior to the collision between the Indian and Eurasian plates. On account of the missing of large propylitic alteration zone and the exposure of the main potassic zone, it is inferred that the depth of erosion in the Gangjiang area could be 23 km. This is similar to the estimation based on the published denudation rate (013023 mm/a) of the Tibetan Plateau. Related Articles | Metrics

Select

Application of comprehensive geologicalgeophysicalgeochemical methods on metallogenic prediction of crisis mines—A case study in Yinan gold deposit. DONG Shu-Xi, GU Xue-Xiang, YANG Yong-Jiang, DI Yu-Sheng, ZHANG Yong-Mei, XIANG Zhong-Lin, LIU Li, HU Gui-Ceng, LI Zhong-Beng 2010, 17(2): 198-208.  Abstract ( 2122 )   PDF (2843KB) ( 1268 )    As a typical skarn deposit in the western Shandong Province, the Yinan gold deposit is becoming a serious crisis mine after more than 50 years of exploitation. The serious shortage of reserves turns the search for succeeding resources into a top priority. Relying on the project of mineral resource prediction on crisis mines, under the guidance of metallogenic system theory, the authors collected and repeatedly developed a large number of geological data, according to which the metallogenic geological conditions and orecontrolling factors were comprehensively analyzed, and the metallogenic laws were summarized. On the basis of largescale traverse geological survey and geological mapping, two forecast targets were selected in the periphery of the mining area. Combined with metallogenic prediction using targeted comprehensive methods including geology, geophysics, geochemistry, etc., industrial ore bodies had been found on the unconformity surface, providing new bases of succeeding resources for the mine and prolonging the mine life effectively. Successful orefinding by drillverifying in two predicted targets, in particular, the discovery of the unconformity related mineralization, not only suggests the huge oreforming potentials in deep and periphery of the Yinan deposit, but also is of great significance to the study of metallogenesis and exploration both in the mine and in the entire western Shandong Province. Related Articles | Metrics

Select

The geochemical features of primary halo and the evaluation of deep mineralization prospect of Liubagou gold deposit, Inner Mongolia. ZHANG Yong-Mei, GU Xue-Xiang, CHENG Wen-Bin, DONG Shu-Xi, JING Liang-Bing, WANG Li-Jiang, ZHANG Yan 2010, 17(2): 209-221.  Abstract ( 2428 )   PDF (2867KB) ( 2576 )   The geochemical features of primary halo of Liubagou gold deposit are systematically discussed in the paper, using multivariate statistical methods combined with geochemical parameters information; the anomalous features of primary halo are outlined and the axial zoning sequence of elements are established; the extent of denudation is analyzed and the primary halo superimposed model is built. In the western part of Liubagou gold deposit, the front elements are coexistent with the rear elements, and the antizoning of Sb and Bi shows the characteristics of superposition of multistage mineralization, reflecting the existence of blind ore bodies. In the eastern part, the axial zoning sequence is basically normal; the strong fluctuations of geochemical parameters indicate that the blind ore bodies may exist there. While in terms of denudation, the western part ore bodies of the No313 vein has undergone relatively strong erosion, the middle and eastern part have undergone minor denudation. According to the results mentioned above, we predicted that a good mineralization perspective exists in the western part; that for the middle part, the anomalous area is at the elevation of above 1400 m; and that the eastern part is of the best prospect. This study provides important evidence for deep prospecting in the mining district. Related Articles | Metrics

Select

A discussion on the origin of  witherite deposits in largescale barium metallogenic belt, southern Qinling Mountains, China: Evidence from individual fluid inclusion. LIU Jia-Jun, TUN Qing-Hua, LIU Zhen-Jiang, SU Wen-Chao, WANG Jian-Beng 2010, 17(2): 222-238.  Abstract ( 2770 )   PDF (3261KB) ( 1410 )   The barite deposits in which Ba presents as BaSO4 are widespread in the world, whereas the witherite deposits in the presence of BaCO3 are rarely reported. Numerous layered witherite and barite deposits occur within the Early Paleozoic silicate formations of southern Qinling Mountains. These two types of deposits, representing a largescale particular metallogenic belt in the world, exhibit paragenetic and separated distribution characteristics. This paper focuses on the fluid inclusion features of witherite, barytocalcite, barite, and quartz in the barium metallogenic belt. The results indicate that the homogenization temperature of fluid inclusions of each mineral ranges from 90 to 310 ℃, mainly concentrating at the range of 120220 ℃. For all that, the peak of forming temperature of witherite and barytocalcite is higher than that of barite about 40 ℃, and quartz forming temperature distributes more homogeneously, and does not appear peak. The salinity of fluid inclusions of most minerals ranges from 1 to 15 wt% NaCleqv, but the salinity of fluid inclusions of witherite, barytocalcite, and quartz generally is more than 5 wt% NaCleqv, while for a considerable proportion of barite, the salinity of fluid inclusions is less than 5 wt% NaCleqv. The fluid inclusions of the barite mainly are of NaClH2O type, whereas the fluid inclusions of witherite are rich in aqueous solution with complicated components like N2CO2H2SCH4 etc., which shows that there is a large difference between the metallogenic environments of witherite and barite. Based on these evidences, we suggest that the thermochemical sulfate reduction (TSR) of the solution was the main formation mechanism of witherite deposits. Related Articles | Metrics

Select

Oreforming fluid characteristics and genesis of silverleadzinc deposits in the Manzhouli area, Inner Mongolia, China. WU An, MEI Mei, GAO Feng-Jun, LI Zong-Pan, JIAO Cui-Jie 2010, 17(2): 239-255.  Abstract ( 3324 )   PDF (2975KB) ( 1166 )   The Manzhouli area located in the northeastern part of Inner Mongolia is the most important AgPbZn metallogenic province in the Derbugan metallogenic belt. In this paper, the authors systematically studied the fluid inclusions of the AgPbZn deposits and discussed their ore genetic types with the Erentaolegai and Chaganbulagen deposits as examples. In the Erentaolegai Ag deposit, the fluid inclusions are characterized by aqueous twophase inclusion, with homogeneous temperatures of 242 to 334 ℃ (averaging 265 ℃), salinities of 173 wt% to 448 wt% NaCleqv (averaging 270 wt% NaCleqv) and densities of 072 to 084 g/cm3 (averaging 080 g/cm3). In the Chaganbulagen AgPbZn deposit, fluid inclusions can be classified into types of aqueous twophase, CO2bearing and pure CO2; their homogenization temperatures, salinities and densities range from 179  to 367 ℃ (averaging 261 ℃), 223 wt% to 687 wt% NaCleqv (averaging 435 wt% NaCleqv) and 065 to 091 g/cm3 (averaging 082 g/cm3), respectively. The oreforming pressures of the Erentaolegai and Chaganbulagen deposits varied from 13 to 26 MPa with an average of 18 MPa and from 15 to 46 MPa with an average of 25 MPa, respectively, corresponding to oreforming depths of 05 to 10 km with an average of 07 km and 06 to 17 km with an average of 09 km, respectively. The oreforming fluids of the both deposits were characterized by lowtomoderate temperature, low salinity and moderate density. The oreforming fluids of the Erentaolegai and Chaganbulagen deposits generally belonged to H2ONaCl and H2OCO2CH4NaCl fluid systems, respectively. The oreforming fluid of the Erentaolegai Ag deposit was mainly composed of meteoric water, and its genetic type belonged to epithermal. The oreforming fluid of the Chaganbulagen AgPbZn deposit consisted mainly of mixed water between magmatic water and meteoric water. And its origin belonged to epithermaltomesothermal lode deposit, and immiscibility or boiling action of oreforming fluid was the dominant factor for silver, lead and zinc deposition. The AgPbZn deposits were closely related to the volcanic and/or subvolcanic hydrothermal solutions of the late stage of the Late JurassicEarly Cretaceous volcanicmagmatic activity. The mineralization period of the AgPbZn deposits in the Manzhouli area was in the Early Cretaceous, those deposits occurred in the Mesozoic intracontinental volcanofault basin with an extensional tectonic setting. Related Articles | Metrics

Select

Formation mechanisms for three forms (Th>Tm, Th=Tm and Th<Tm) of moderate and highsalinity NaClH2O fluid inclusions and physicalchemical conditions during their entrapment. CHEN Wen-Meng, WANG Yong, CHEN Wei-Shi 2010, 17(2): 256-265.  Abstract ( 1732 )   PDF (3389KB) ( 1379 )    It is proposed for the first time that the three forms (Th>Tm, Th=Tm and Th<Tm) of moderate and highsalinity NaClH2O fluid inclusions trapped homogenously are mainly determined by their phase states (homogeneous or inhomogeneous) and the relationships between ΔVl (variation in volume of NaClH2Osaturated fluids) and ΔVs (variation in volume of salts) caused by the process of temperature decrease and increase after entrapment of the inclusions. During homogeneous entrapment of NaClH2Osaturated fluids, if ｜ΔVl｜＞｜ΔVs｜, i.e. the inclusions trapped at the temperature less than the temperature range at the Tr point (which is the temperature at ｜ΔVl｜＝｜ΔVs｜) on the NaCl saturation curve, the inclusions have Th=Tm, where Th or Tm is the temperature during their entrapment. If ｜ΔVl｜≤｜ΔVs｜, i.e. the inclusions trapped at the temperatures equivalent to or higher than the temperature range at the Tr point on the NaCl saturation curve, the inclusions have Th＜Tm, where Tm is the temperature during their entrapment and Th has a negative correlation with pressures during entrapment. During homogeneous entrapment of NaClH2Oundersaturated fluids, i.e. when the temperature is higher than that at the saturation point and the inclusions trapped at the densities less than the density ranges at the saturation point, the inclusions have Th＞Tm, where Th is the lowest temperature during entrapment of this type of inclusion. When the inclusions trapped at the temperatures and densities less than those on the isochore at the Tr point, the inclusions have Th<Tm, where Tm is the lowest temperature during entrapment of this type of inclusion and Th has a negative correlation with the pressures during entrapment. When the inclusions trapped at the temperatures and densities greater than those on the isochore at the Tr point, the inclusions have Th=Tm, where Th or Tm is the lowest temperature during entrapment of this type of inclusion. During inhomogeneous entrapment of NaClH2Osaturated fluids, both Th and Tm are higher than or equal to the entrapment temperature. The relationship between Th and Tm is determined by the volume ratio of crystals to vapor bubbles. In this paper the Tr value under the standard conditions (one atmospheric pressure and 25 ℃) of vaporliquid equilibrium is determined through thermodynamic calculations to be 335 ℃. It is suggested that the entrapment environments of this type of inclusion (homogeneous or inhomogeneous) can be distinguished by calculations of Tr values at different temperatures and the ratios of Vl, Vs and Vg at normal temperatures and pressures. Related Articles | Metrics

Select

Axi gold deposit: A Paleozoic lowsulfidation type of epithermal gold deposit in Xinjiang, China.  DI Wei, SUN Xiao-Meng, SU Li-Wei, HE Xiao-Beng, TUN Wei-Liang 2010, 17(2): 266-285.  Abstract ( 2661 )   PDF (3781KB) ( 1966 )   Axi gold deposit, occurring in the Tulasu volcanic faultbasin in the Paleozoic activecontinentalmargin on the north side of the YiliCentral Tianshan Plate, is a lowsulfidation type of epithermal gold deposit formed in the Paleozoic era. The host rocks are andesitic and volcaniclastic rocks of the Paleozoic Dahalajunshan Formation, and the ore bodies occurred as veins in annular faults of an old caldera. Orerelated minerals consist mainly of native gold, electrum, pyrite, marcasite, arsenopyrite, hematite, limonite, and trace amounts of pyrargyrite, naumannite, polybasite, cerargyrite, etc, whereas gangue minerals consist mainly of quartz, chalcedony, sericite, calcite, siderite, adularia, etc. The main wallrock alterations were silicification, phyllic alteration, carbonatization and propylitization. The deposit is characterized by enrichments of Au, Ag, As, Sb, Bi, Hg, Se, Te and Mo relative to average crust, and low Ag／Au ratios (046111). The compositions of hydrogen, oxygen, carbon, sulfur and noble gas isotopes indicate that oreforming fluids of the Axi gold deposit consisted predominantly of circulating meteoric water. The salinities of oreforming fluid vary mainly from 07 to 31 wt％ NaCleqv, with an average of 22 wt％ NaCleqv. The homogenization temperatures are mainly of 120 to 240 ℃, with an average of 190 ℃, the fluid density is 073 to 095 g/cm3, and thus the estimated maximum mineralization depth is about 700 m. The boiling of the oreforming fluid had occurred, leading to the supersaturation of the hydrothermal solution and the deposition of ore metals. This is the main mineralization mechanism for quartzvein type ores in Axi. The oreforming fluid was buffered to a nearneutral pH in a reduced environment during mineralization. Geochemical and geological characteristics show that Axi is a typical Paleozoic lowsulfidation type of epithermal gold deposit. The preservation of this Paleozoic Axi deposit required a rapid covering by the sedimental cover of Aqialehe Formation after the formation of the deposit. Beginning in the Pliocene, the Tianshan had dominated by rapid thrusting and uplifting as a result of the collision and compression between India and Eurasia, which led to part of the deposit cover being eroded and the deposit reemerged. The discovery of Axi is therefore critical for guiding the exploration of epithermal gold deposits in preMesozoic orogenic belts. Related Articles | Metrics

Select

The evidence from fluid inclusions for the immiscibility of the oreforming fluids in the Shuiyindong gold deposit, Guizhou Province. LI Bao-Hua, GU Xue-Xiang, FU Chao-Hong, XU Shi-Hai, CHEN Cui-Hua, DONG Shu-Xi 2010, 17(2): 286-294.  Abstract ( 2458 )   PDF (1308KB) ( 1242 )    Based on the microthermometry and thermodynamic parameters of fluid inclusions in the Shuiyingdong Au deposit, we have studied the thermodynamic conditions of the immiscibility of the oreforming fluids. The results show that the fluid inclusions in quartz are divided into three categories: H2O inclusions, CO2 inclusions and CO2H2O inclusions. The CO2H2O inclusions can be further classified into H2Orich CO2H2O inclusions and CO2rich CO2H2O inclusions. When heated, the homogeneous phase state of H2Orich CO2H2O inclusions was the H2O phase, while that of CO2rich CO2H2O inclusions was the CO2 phase. Moreover, they have the same homogeneous temperature and pressure. This suggests that they were CO2 and lowsalt water immiscible fluid inclusions having been trapped in the same period. The thermodynamic conditions of their formation are the formation temperature of 236  ℃, pressure of 324 bar, lowsalt water phase density 0900 g/cm3, CO2 phase density 0314 g/cm3, the CO2 mole fraction of 00376 in lowsalt water phase and 07337 in CO2 phase, and aqueous solution salinity w(NaCl)≈13％. Related Articles | Metrics

Select

A study of oreforming fluid features and metallogenesis of 1# vein from Xiaotazigou gold deposit, Chaoyang city, Liaoning Province. LI Bi-Le, HU Qiang-Lin, ZHANG Han, CHANG Guo-Lin 2010, 17(2): 295-305.  Abstract ( 2083 )   PDF (2308KB) ( 1135 )   The studied area is located in the middle section of the north margin of North China craton, which is one of the most important gold and nonferrous metal metallogenic belts. In the Xiaotazigou ore district, the hosted rocks of gold deposit are the Archean metamorphic complex of Xiaotazigou formation, and the orebodies are primarily hosted in EWstriking and NEstriking fractures, while Beidashan monzonitic granite body is closely associated with metallization. The ore natural type of 1# vein is the quartz vein type; its economic value is the highest in the ore district. Fluid inclusions of quartz crystals in 1# vein can be classified into types of aqueous twophase, CO2rich three phase and pure gas. The salinities of fluid inclusions range from 2.06% to 11.72% NaCleqv，concentrating in three ranges of 2.06%3.37% NaCleqv，4.69%6.97% NaCleqv and 9.86%11.72% NaCleqv. The densities of fluid inclusions range from 0.689 to 0.977 g/cm3. The homogenization temperatures of fluid inclusions range from 174 ℃ to 348 ℃，concentrating in two ranges of 302348 ℃ and 174187 ℃. During the early oreforming stage, the oreforming fluids were characterized by high temperature, low salinity, and the coexistence of CO2rich three phase and aqueous twophase. The reason for the coexistence is that the mixture of two different kinds of fluids caused nonuniform capture. During the middlelate oreforming stage, the oreforming fluids were characterized by the fall in temperature，and the rise in salinity. The abrupt fall in temperature resulted in boiling characterized by CO2 loss, from which the salinity and the density of remnant fluids were raised. According to the diagram of coexistence surface，the oreforming pressure can be calculated and it is in the range of 1628 MPa, the oreforming depth is in the range of 1.62.8 km. In contrast to other orogenic gold deposits worldwide, Xiaotazigou gold deposit is defined as epizonal orogenic gold deposit and the intracontinent collision was its metallogenic dynamic background. Related Articles | Metrics

Select

LAICPMS in situ trace element analysis of pyrite from the Xinqiao CuAuS Deposit in Tongling, Anhui, and its constraints on the ore genesis. ZHOU Chao-Fa, ZHANG Le-Jun, YUAN Feng, FAN Yu, David R.Cooke 2010, 17(2): 306-319.  Abstract ( 2859 )   PDF (3043KB) ( 2025 )   As a newlydeveloped microanalytic technique, Laser ablation inductively coupled plasma mass spectrometry (LAICPMS) of sulfide minerals can provide us important informations regarding the nature of oreforming fluids, ore genesis and their implications on mineral exploration. Pyrites from Xinqiao CuAuS deposit in the Tongling mineralization belt, Anhui Province, China, have been selected for detailed study in this paper. Three types of pyrite were recognized through detailed field work and paragenetic studies, among which the earliest colloform pyrite, termed PyI, is interpreted as sedimentary in origin, whereas PyII is mainly composed of fine grained, anhedral crystals with some characteristics of deformation and recrystallization. Mediumcoarse grained and euhedral PyIII is inferred to be the result of hydrothermal activities and associated with mineralization. The LAICPMS analyses of three types of pyrite indicate that the sedimentary PyI contains the highest values of Ti, Co, Ni, As, Se, Te. PyII pyrite also is rich in Ti, Co, Ni, As, Se, Te，with variable content of oreforming elements such as Cu, Pb, Zn, Au and Ag. PyIII shows distinguished composition compared to other two types of pyrite. Cu, Pb, Zn, Au, Ag and Bi give much higher ranges in PyIII but Co, Ni and As are relatively lower. Evidences show that Co, Ni, As, Se and Te are contained in pyrite as isomorphous solid solution. Bi occurs as Bicontaining minerals which are commonly small inclusions in PyII pyrite, however, in PyIII, Bi partially replaced Fe in lattice. The oreforming elements, e.g. Cu, Pb, Zn, Au and Ag in Xinqiao deposit mainly occurred in PyIII. Cu and Zn are mainly represented by chalcopyrite and sphalerite inclusions enclosed in pyrite. Au and Ag in PyII, albeit with low content, probably occur as inclusions of freegold and freesilver. However, in PyIII, electrum is the major mineral containing Au and Ag, which is also possibly in bismuth minerals. Pb occurs in both galena and bismuth minerals inclusions in pyrite. Textures, paragenesis and trace element geochemistry of pyrite indicate that PyI was formed in the process of the Late Paleozoic submarineexhalative sedimentation, which was supported by other studies, whereas PyII and PyIII pyrite may occur during the Mesozoic tectonic transitiondeformation and subsequent hydrothermal superimposition, respectively. Therefore, the formation of Xinqiao CuAuS deposit may have recorded both the late Paleozoic submarine or exhalation sedimentation and hydrothermal telescoping in the Mesozoic. Colloform pyrite with rare Cu and Au mineralization deposited during sedimentation, while most of economic metals, e.g., Cu, Pb, Zn, Au and Ag, were introduced through hydrothermal fluids during emplacement of the Yanshanian dioritic intrusions.  Related Articles | Metrics

Select

A study of mineralogy and petrochemistry of Jijie alkalineultramafic rocks, southern part of Panxi rift. DIAO Zheng, QI Liang, HUANG Zhi-Long, YAN Zai-Fei, HU Cheng 2010, 17(2): 320-335.  Abstract ( 2138 )   PDF (2413KB) ( 993 )   This paper reports the lithofacies, mineralchemistry and petrochemistry of alkalineultramafic rock complex in Jijie, the southern part of Panxi rift, Yunnan Province. Clinopyroxene and nepheline are the main component minerals, which have negative correlations in melteigite, ijolite and urtite. The Fo value of xenocryst olivine(75.4377.42) is obviously higher than that of the phenocryst olivine(72.0272.95) in melteigite, which suggests that the parent magma had undergone a previous olivine crystal differentiation. The prevalent zone structure in clinopyroxene, and the package structure and reaction edge structure between clinopyroxene and olivine indicate a relatively rapid ascent and crystallization progress of the parent magma. The characteristics of the major elements and related parameters (M, CA, AR, SI, DI) suggest that the parent magma of Jijie complex was strongly Siundersaturated, Narich alkaline magma. The well linear correlation between MgO and other oxides in Harker diagram indicates that olivine and clinopyroxen were the main crystalline phase during the magma fractionation. The well linear correlation between lgSI and the compositions of major oxides suggests that there was no or little crustal contamination during the magma evolution.    Related Articles | Metrics

Select

The geochemical characteristics of PGE，siderophile and chalcophile elements of Jinchanggouliang gold (copper) deposits, Inner Mongolia, their provenance and oreforming tectonic setting. LI Yi-Xin, SUN Jing-Gui, CHEN Jun-Jiang, MEN Lan-Jing, NIE Chi-Chao, ZHANG Peng 2010, 17(2): 336-347.  Abstract ( 2579 )   PDF (1937KB) ( 1269 )    In this study, we provide a novel method which combines the technique of oremelting blocked by HCl（aq） and H2O2 with the ICPMS for the first time to determine the amount of Platinum metal group elements (PGE), siderophile elements and chalcophile elements in the typical ore in the East and West ore fields of Jinchanggouliang gold (copper) deposits. The experimental results show that the content of these elements in the ore is higher than the detection limit of the test technique, especially for the PGE. The geochemical evolution characteristics of these elements indicate the orebearing fluid having the magma properties. The characteristics of PGE prove the fact that the primitive mantlenormalized PGE shows a strong leftinclined fractional patterns, which is similar to the copperrich sulphide melt and nickelsulphide melt associated with mantlederived magma, and to the mantlederived basalt and carbonate melts, so we suggest that the orebearing fluid has the properties of mantle magma fluid. Considering the regional structural, magmatic and thermal events, and combined with the geochemical characteristics of reported typical porphyry copper (molybdenum) deposits, we may draw the conclusion that the orebearing fluid formed in the Mesozoic continental marginal environment, and the thermal dynamic source may have been derived from the underplating basaltic magma. The Pd/Pt and Pd/Ir ratios of Au and Curich ore samples are close to those of lowtitanium basalt and basaltic andesite for the oreforming stage, but the ratios of the Au and Cupoor samples are close to those of the mantle endmember for the early mineralization stage, which indicates the early orebearing fluid may directly come from the differentiation and crystallization of Mesozoic basalt magma, while the Au and Curich fluid may have been produced by the separation of the fluid from the supercritical fluidrich magma (low Ti magma), which was formed in the later evolution stage of basalt magma with contamination by crustal materials. The PGE geochemical activity in the orebearing fluid evolution process was related to the saturation of copper or sulfur (arsenic), that is, it was controlled by chalcophile elements or crystallized mineral facies of sulfides. Related Articles | Metrics

Select

REE geochemistry of garnets from the Langdu skarn copper deposit. LIN Chao, ZHONG Hong, ZHANG Xin-Chun, SHU Wei-Guang 2010, 17(2): 348-358.  Abstract ( 4177 )   PDF (2257KB) ( 6311 )   This study focuses on major and rare earth element compositions of garnets from the Langdu skarn copper deposit. Electron microprobe analyses show that the garnets from the Langdu deposit belong to grossularandradite solid solution ranging in composition from Ad87Gr13 to Ad92Gr8. The garnets from the Langdu deposit are characterized by much lower ∑REE content and LREEenriched and HREEdepleted pattern, with a significantly positive Eu anomaly, which is obviously different from those of the majority of skarn deposits worldwide. The present study indicates that the andradites from the Langdu deposit grew rapidly and were not in complete equilibrium with the oreforming fluids, indicative of high W/R ratios. Under such conditions the incorporation of REE in andradites was controlled by crystal kinetics (surface adsorption and occlusion) and the REE pattern of the magmatic fluid.  Eu2+(r=125 ) has a bigger ionic radius than the other REE3+, making it easier to be adsorbed by garnet crystals, which could have been the dominant control on the strongly positive Eu anomaly in garnets of the Langdu deposit. Related Articles | Metrics

Select

The fluid inclusions and C, H and O isotopic geochemistry of the  Mineralized Zone No1 at the Halasu copper deposit, Xinjiang. YANG Fu-Quan, YAN Sheng-Hao, JUE Wen-Dun, ZHOU Gang, LIU Feng, GENG Xin-Xia, LIU Guo-Ren, WANG Xiang 2010, 17(2): 359-374.  Abstract ( 2419 )   PDF (2515KB) ( 1267 )   The  Mineralized Zone NoI at the Halasu copper deposit in Qinghe County is situated in Kalaxiangeer porphyry copper belt. The copperbearing minerals mainly occur in the form of heterogeneous gobbets, veinlets and veinletdisseminated in the granodiorite porphyry, quartz diorite porphyry, basalt and pyroxene phenocrysts basalt. Two types of fluid inclusions, namely H2O-NaCl and H2O-CO2 (±CH4/N2)NaCl types, have been recognized in quartz and calcite from the ore. Homogenization temperatures of fluid inclusions vary from 120 to 431  ℃, with three temperature peaks at 390,290 and 190 ℃. Salinity ranges from 053% to 6676 ％ NaCleqv, with four peaks at 19.5％ NaCleqv, 12.5％ NaCleqv, 9.5％ NaCleqv and 1.5％ NaCleqv. Ore fluid densities range from 055 to 1.11 g/cm3. The δ18OSMOW values of quartz and calcite in the ore vein range from 2.9‰ to 12.3‰ with corresponding δ18Ofluid values of -5.81‰ to 4.83‰ and δD values of fluid inclusions between -129‰ and -80‰. The isotopic data imply that the oreforming fluids of the Halasu copper deposit were mainly derived from magmatic fluids, with some contributions from meteoric water. The δ13CPDB values of calcite define a narrow range of -2.4‰ to -1.4‰ and δ18OSMOW values range from 8.3‰ to 9.2‰ indicating that the carbon in the ore fluids was mainly derived from magma. ReOs dating was performed on molybdenite from molybdenite vein, which yielded isochron ages of (378.3±5.6) Ma. This isochron age is coincident with the age of 381375 Ma from granodiorite porphyry pluton within error range. Early mineralization formed in the Middle Devonian, which was closely related to porphyry systems. The LateMiddle tectonicmagmatichydrothermalmineralization overlapped the early porphyry mineralization in the Halasu copper deposit. Related Articles | Metrics

Select

Geology and sulfur isotope geochemistry of leadzinc deposits in Luanchuan district, Henan Province, China. DUAN Shi-Gang, XUE Chun-Ji, LIU Guo-Yi, YAN Chang-Hai, FENG Qi-Wei, SONG Yao-Wu, CHU Ji-Jun 2010, 17(2): 375-384.  Abstract ( 2715 )   PDF (2054KB) ( 1896 )   The Luanchuan district in Henan Province is known as a porphyry molybdenum concentrated area in China. Recently, numerous leadzinc lodes have been found there. However, there are many divergent opinions on the genesis and controllingfactors of these leadzinc deposits. The leadzinc deposits in Luanchuan district are distributed around the Yanshannian porphyry molybdenum intrusions and hosted in a metamorphic sedimentary formation consisting of terrigenous clastic rock and carbonatite of either mesoproterozoic age (the Guandaokou group) or neoproterozoic age (the Luanchuan group), which is intruded by neoproterozoic (Jinning stage) gabbro and syenite and Yanshannian acidic porphyries. The leadzinc deposits are of vein or lenticular shape, and can be divided into three types: (1) the skarn type leadzinc deposits controlled by the contact zone between Yanshannian porphyries and proterozoic calcareous strata; (2) the veintype leadzinc deposits controlled by the WNW interlayer fault; (3) the veintype leadzinc deposits controlled by the NENNE extensional torsional fault. The sulfur isotope compositions of sulfides suggest the following points of information: (1) the δ34SVCDT of sulfides in leadzinc ores are positive values that close to 0‰, which appear obviously to have had a source of magmatic sulfur (Luotuoshan deposit=0.37‰4.20‰, Chitudian deposit=-032‰830‰, Bailugou deposit=-1.20‰10.90‰, Lengshuibeigou deposit=0.70‰12.10‰); (2) the δ34SVCDT of the sulfides of skarn leadzinc ore are very close to that of the sulfides in porphyry molybdenum ore (1.24‰3.30‰), and the δ34SVCDT of the sulfides of veintype leadzinc ore overlap mostly with that of the sulfides in porphyry molybdenum ore but influenced by the sulfur in the wallrock (δ34SVCDT=12.43‰1863‰); (3) as a whole, δ34Spyrite>δ34Ssphlaerite>δ34Sgalena, which shows the sulfur isotope fractionations of the dominating sulfides in leadzinc ore basically reach equilibria, and a pair of paragenetic sphalerite and galena from Chitudian deposit gives a high sulfur isotope equilibrium temperature of 38829 ℃. All the above suggest that the leadzinc deposits in Luanchuan district, Henan Province, are principally meso to hypothermal leadzinc deposits controlled by Yanshannian structuralmagmatic activity. Related Articles | Metrics

Select

REE and stable isotope geochemical characteristics of Bojitian gold deposit, Guizhou Province. ZHANG Yu, JIA Yong, WANG Ze-Feng, YAN Bao-Wen, FU Zhi-Kang, CHEN Meng 2010, 17(2): 385-395.  Abstract ( 2221 )   PDF (1640KB) ( 1013 )   The Bojitian gold deposit is located in the east of Huijiabao anticline and is an important component of Huijiabao ore field. Gold mineralization occurred under low temperature and was closely associated with decarbonation, silicification, sulfidation and dolomitization. The deposit has a characteristic elemental assemblage of AuAsHg. Calcite mineralization with MREE enrichment and positive Eu anomalies characteristic show that the oreforming hydrothermal fluid might be a reductive fluid with a MREE relative enrichment and positive Eu anomalies. The oreforming fluid mainly originated from a plutonic source, and at least had undergone the fluidrock interaction for a plagioclaserich area. The δ13C value of -6‰-01‰ for the calcite vein formed in the oreforming stage and the δ13C value of 0.2‰3.2‰ for the calcite vein formed post the oreforming stage indicate that the carbon in the oreforming stage was from the mantle and the formation, and that the carbon post the oreforming stage was from the formation. The δ34S value of realgar varying from 073‰ to 586‰ with the characteristics of mantlederived sulfur indicates that the isotopic composition of sulfur of sulfides in the deposit is highly homogeneous. In general, we suggest that the orebearing materials and fluids of the gold deposit mainly originated from a plutonic source. In the Yanshan period, the oreforming fluids upwelled along the deep fault; when they were transported to the anticline core, the oreforming conditions were greatly changed, which led to the rapid enrichment and precipitation of gold and the formation of the Bojitian gold deposit. Related Articles | Metrics

Select

Characteristics of isotopic geochemistry of Shuiyindong superlarge Carlin gold deposit in Guizhou. WANG Cheng-Hui, WANG De-Gong, LIU Jian-Zhong, DENG Yi-Meng, LIU Chuan-Qi, LI Jian-Kang, CHEN Fa-En 2010, 17(2): 396-403.  Abstract ( 2209 )   PDF (1398KB) ( 1181 )    The Shuiyindong deposit is a superlarge gold deposit in Southwest Guizhou Province, which is famous for its high grade and super largescale. The geochemical study of isotopes such as S, Pb, C and O shows that the oreforming material may come from juvenile fluids and crustal rocks. Some isotopic data from other carlin deposits in YunnanGuizhouGuangxi area indicate that the mineralization of gold deposits in this area may closely relate to the evolution of juvenile fluids and some rocks that may be concealed under this area. Related Articles | Metrics

Select

Recollection of the forepart study of environmental quality geochemistry: To the memory of the Prof. Tu Guangchis 90 birthday. MO Guo-Jiang 2010, 17(2): 404-416.  Abstract ( 1776 )   PDF (1553KB) ( 889 )   Prof. Tu Guangchi, an academician of CAS, predicted in 1973 that “the environmental sciences and life sciences will be  uprising in the 70s of 20 century”, and pointed out that “the mutual infiltration between environmental sciences and geochemistry has produced the environmental geochemistry, as a new interdisciplinary subject”. In the past 40 years, the development of the Environmental Quality Geochemistry has undergone three stages: the “investigationevaluation” stage, the “regionintegration” stage and the “interfacemechanism” stage. The environmental geochemistry focused its research objective on the regional evolution of environment, as well as the environmental impact on health and ecology; it has had remarkable achievements in these studies and it will make more welfare to the mankind in the 21 century. Related Articles | Metrics

Select

Nitrogen isotope as a tracer in atmospheric environment and bioindicators. XIAO Hua-Yun, LIU Cong-Jiang 2010, 17(2): 417-425.  Abstract ( 1637 )   PDF (961KB) ( 1217 )   Atmospheric processes such as transfer, transformation and deposition of nitrogen are closely related to the biogeochemical cycle of nitrogen in the earths surface. Nitrogen isotope as a tracer to determine nitrogen sources and to quantitatively study the atmospheric nitrogen processes is paid close attention to now. This paper briefly described the isotopic characteristics of potential nitrogen sources, the nitrogen isotope fractionation mechanism during atmospheric processes, and the methods of quantitatively studying the atmospheric nitrogen processes. As a new tool used to study nitrogen processes in the atmosphere, the new findings from nitrogen isotope in mosses was also introduced. Detailed introduction to the researches related to nitrogen isotope in the atmosphere and mosses conducted in China was emphasized in this paper. Related Articles | Metrics

Select

Ecological geological systems and their types, position in the ecosystems structure and tasks of the investigation. V. T.Trofimov, T.V.Andreeva 2010, 17(2): 425-438.  Abstract ( 2134 )   PDF (1729KB) ( 967 )   This paper explains the constituent factors comprising ecological geologys field of study and determines the correlation of ecological geology to geoecology. The theoretical basis of ecological geologyclassification of the ecological functions of the lithosphere is exposed. Ecological geologys object of study is expressed as the ecological geological systems found within a specific volume of the lithosphere and acting in or on its surface biota, including human beings and society. Contents of the four types of ecological geological systems—natural real, natural ideal, natural technical ideal, and natural technical real—are characterized. The position of the ecological geological system in the structure of ecosystem is presented. Factors of ecological geological systems formation, substantial typical and scientific tasks relevant to their investigation, the whole range of criteria and indices necessary under ecological geological systems investigation, and complications arising in their study are described. Related Articles | Metrics