Archive

2018, Volume 25 Issue 6
30 November 2018 Previous Issue    Next Issue

---

For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Select

2018, 25(6): 1-0.  Abstract ( 100 )   PDF (7641KB) ( 431 )     References | Related Articles | Metrics

Select

Isotopic mapping and deep material probing(Ⅰ): revealing the compositional evolution of the lithosphere and crustal growth processes. WANG Tao,HOU Zengqian 2018, 25(6): 1-19.  DOI: 10.13745/j.esf.sf.2018.11.21 Abstract ( 465 )   PDF (5294KB) ( 1025 )   One of the important tasks of solid-earth science is to detect deep earth processes and co-evolution of different layers. Deep material probing, geophysical structural probing and deep drilling are the three main approaches in deep-earth exploration. “Magmatic rock probe” or lithospheric probe, and isotopic mapping (such as by whole rock Nd and zircon Hf) are powerful tools for deep material probing. This method has been used to reveal deep composition and structure and their spatio-temporal evolution, determine different crust provinces (ancient or juvenile), delineate terrane boundary, estimate mechanisms and degree of continental crust growth, and analyze regional metallogenesis. Their increasing application can lead to deep material mapping through a combination of deep structural and material probing. The Chinese mainland and adjacent areas are good testing ground for deep material probing. The major unsolved problems include compositions and structures of the lithosphere and continental crust made up of multiple blocks, crustal growth processes and compositions and structures of different types of orogenic belts, and compositions of different tectonic units and their constrains on mineralization. In this paper, we reviewed and discussed research ideas, methods and focuses related to regional isotopic mapping (using whole-rock Sr-Nd and zircons Lu-Hf isotopic probes) and xenocrystic and inherited zircon mapping. We also discussed future key research areas and directions. Related Articles | Metrics

Select

Isotopic mapping and deep material probing (Ⅱ)：imaging crustal architecture and its control on mineral systems. HOU Zengqian,WANG Tao 2018, 25(6): 20-41.  DOI: 10.13745/j.esf.sf.2018.11.19 Abstract ( 532 )   PDF (9687KB) ( 1056 )   The deep Earth is the “engine”, “supply source” and “transfer belt” for large-scale mineralization. The mineralization process, therefore, is best understood by revealing deep material composition and distribution, deep material cycle and energy conversion, and deep crustal three-dimensional structure and dynamic process. Magmatic rock “probe”, or lithoprobe, and regional isotopic mapping (such as whole rock Nd and in situ zircon Hf isotope) are the main techniques used for exploring compositional and evolutionary processes of deep Earth. These probing techniques can detect deep crustal composition and three-dimensional architecture to reveal the spatial distribution and temporal evolution of the new, old and recycled crust, providing deep Earth constrains on regional metallogenic regularity to assist quantitative and semi-quantitative evaluation of metallogenic potential and improve regional prediction model. Here, we examined magmatic whole-rock Nd and zircon Hf isotopic mapping in solving deep crustal three-dimensional structure and its control on metallogenesis, and discussed the developmental mechanism of massive magmatic rock deep inside Earth and its metallogenic constraints. We also examined the deep crustal architecture and its control on mineralization of different-types of orogens (e.g., the Central Asian accretionary orogenic belt, the Qinghai-Tibet plateau collisional orogen and the Qinling composite orogen) and several cratons. The results show that the distribution of copper, gold, copper and nickel deposits is controlled by the distribution of juvenile crust independent of orogenic belt and craton types. They also show that large-scale molybdenum and lead-zinc ores as well as rare metals and other minerals occur in old crust, and iron ores often developed in the transition zone between the old and new crust. In addition to revealing the regional metallogenic rules, our findings may applicable in metallogenic prediction and metallogenic potential evaluation, an expected new direction for studying regional metallogenic regularity including especially studies of detection and metallogenic background of deep crustal material. Related Articles | Metrics

Select

Discussion on the tonalite-trondhjemite-granodiorite (TTG) petrotectonic assemblage and its subtypes. DENG Jinfu,LIU Cui,DI Yongjun,FENG Yanfang,XIAO Qinghui,LIU Yong,DING Xiaozhong,MENG Guixiang,HUANG Fan,ZHAO Guochun,WU Zongxu 2018, 25(6): 42-50.  DOI: 10.13745/j.esf.sf.2018.10.3 Abstract ( 546 )   PDF (1562KB) ( 685 )   The TTG petrotectonic assemblage (or igneous series) characterizes subduction of oceanic crust. In this paper, we suggest four subtypes of the TTG series: (1) The magnesium andesite (MA) lower pressure subtype is formed at a subduction zone of very young oceanic crust at highest temperature, ≤15001600 MPa pressure and ≤5060 km depth, for example, at the margins of the slab-window of the active mid-oceanic ridge subduction. (2) The magnesium andesite (MA) higher pressure subtype is formed at a subduction zone of relatively young oceanic crust at high temperature, ≥15001600 MPa pressure and ≥5060 km depth. (3) The lower (or non) magnesium andesite (LMA) lower pressure subtype is formed at a lower crust of the intra-oceanic island arc at ≤15001600 MPa pressure and ≤5060 km depth. And (4) The lower (or non) magnesium andesite (LMA) higher pressure subtype is formed at the mountain root of the continental arc at ≥15001600 MPa pressure and ≥5060 km depth. Using a combination of the four TTG assemblage subtypes and non-magma generation at the subduction zone of older oceanic crust at low temperature with or without magma generation at the mantle wedge, we may reconstruct the crust-mantle and thermal structures of the magmatic arcs and provide a geologic basis for oceanic subduction related mineralization. Related Articles | Metrics

Select

The geologically testable hypothesis on subduction initiation and actions. Yaoling NIU,SHEN Fangyu,CHEN Yanhong,GONG Hongmei 2018, 25(6): 51-66.  DOI: 10.13745/j.esf.sf.2018.11.7 Abstract ( 291 )   PDF (6307KB) ( 659 )   Abstract: The advent of plate tectonics theory 50 years ago has revolutionized Earth Science thinking and provided a solid framework for understanding how the Earth works. This theory explains in simple clarity that all the geological processes are ultimately consequences of Earths cooling. This is well manifested by the origin of oceanic plates at ocean ridges, the movement and thickening of these plates, and their ultimate consumption back into the Earths deep interior through subduction zones, which provides an efficient mechanism to cool the Earths mantle, leading to large-scale mantle convection. That is, the immediate driving force for plate tectonics is the sinking of the cold and dense oceanic lithosphere, under gravity, into the deep mantle through subduction zones. Hence, there would be no plate tectonics if there were no subduction zones, but exactly how a subduction zone begins remains speculative. Studies on subduction initiation have been many and continue to this day by means of numerical simulation and geological inferences, culminating with three IODP expeditions (350, 351 and 352 in 2014) in the western Pacific to test the ideas of spontaneous and induced subduction initiation. All these efforts are welcome, but the ideas are not testable hypothesis. In this paper, we explain the only hypothesis that is geologically testable on subduction initiation, i.e., subduction initiation is a consequence of lateral compositional buoyancy contrast within the lithosphere. Such large buoyancy contrast is located at edges of oceanic plateaus in ocean basins and at passive continental margins globally. Because back-arc basins result from seafloor subduction, all the island arcs must have continental (or oceanic plateau) basement. Hence, this hypothesis can be effectively tested by sampling and studying island arc basement rocks that are exposed on landward trench slopes as the result of serpentinite diapirism. References | Related Articles | Metrics

Select

Magmatic origin of continental arcs and continental crust formation. ZHU Dicheng,WANG Qing,ZHAO Zhidan,NIU Yaoling,HOU Zengqian,PAN Guitang,MO Xuanxue 2018, 25(6): 67-77.  DOI: 10.13745/j.esf.sf.2018.11.11 Abstract ( 905 )   PDF (2895KB) ( 1196 )   How the continental crust is formed has long been a fundamental scientific question for the international academic community. Magmatic origin and density filtering of arcs at active continental margins are crucial to understanding formation and evolution of continental crust. The Cretaceous Cordilleran continental margin arc in North America may have formed through partial melting of lower crust and magma mixing associated with mantle-derived magmatic underplating, or two-stage compositional differentiation of mantle-derived initial basaltic magma. The vertical crustal compositional section that is dominantly granitic in the Nevada region of North America is most likely related to the delamination of eclogite facies residues or cumulates. It is currently not clear that why the Mesozoic Gangdese arc in southern Tibet is characterized by the occurrence of a large amount of hornblendites and the presence of an arc crust with basaltic andesitic composition in average at ca. 200 Ma and ca. 90 Ma. This problem may be resolved more or less by exploring the magmatic origin, vertical crustal compositional profile, and crustal formation mechanism of the Mesozoic Gangdese arc. References | Related Articles | Metrics

Select

The Gangdese arc magmatism: from Neo-Tethyan subduction to Indo-Asian collision. ZHANG Zeming,DING Huixia,DONG Xin,TIAN Zuolin 2018, 25(6): 78-91.  DOI: 10.13745/j.esf.sf.2018.11.14 Abstract ( 343 )   PDF (2725KB) ( 669 )   The Gangdese magmatic arc, located in southern Tibet, was formed during the long-lasting subduction of the Neo-Tethyan oceanic lithosphere and subsequent collision between the Indian and Asian continents, typical of composite continental magmatic arc. Therefore, the arc is a natural laboratory for studying subduction-related magmatism and continental crust growth. Based on a synthesis of available research results, we propose that the Gangdese arc experienced five stages of tectonic-magmatic events during its formation and evolution. The first stage of magmatism occurred before the Late Cretaceous, characterized by normal subduction of the Neo-Tethyan oceanic lithosphere and formation of subduction-related magmatic rocks. The second stage is related to subduction of an active Neo-Tethyan mid-oceanic ridge, featuring extensive Late Cretaceous magmatism and juvenile crustal growth. The third stage of the latest Late Cretaceous arc magmatism occurred during subduction of the residual Neo-Tethyan oceanic lithosphere. The fourth stage of Paleocene to middle Eocene magmatic flare-up resulted from slab roll-back and break-off of subducted Neo-Tethyan ocean during the Indo-Asian collision, marked by significant thickening and partial melting of juvenile and old crusts. And the fifth and latest post-collisional magmatism involved formation of thickened lower crust-derived adakitic rocks and mantle-derived potassic to ultrapotassic volcanic rocks during the late Oligocene to middle Miocene, induced probably by the roll-back and break-off of the deeply subducted Indian lower crust and mantle lithosphere or by convective removal of the thickened Gangdese arc mantle lithosphere. The systematic temporospatial variations of magmatic events and magmatic compositions of the Gangdese arc provide an excellent record of tectonic evolution from the Neo-Tethyan ocean subduction to India-Asia continental collision. References | Related Articles | Metrics

Select

Diachronous collision-closure of the Jinshajiang paleo-ocean basin in the Yangla area: constraints from ages of the granites. ZENG Pusheng,WANG Yanbin,MA Jing,WANG Zhaoquan,WEN Ligang 2018, 25(6): 92-105.  DOI: 10.13745/j.esf.sf.2018.11.12 Abstract ( 207 )   PDF (6272KB) ( 362 )   The Jinshajiang suture is one of the important sutures in eastern Tethys. The Yangla section of the Jinshajiang suture covers the east syntax of the Tibetan Plateau and is an important window for studying the collision-closing process of the Jinshajiang paleo-oceanic basin. Based on previous investigations and through field sampling and observation, combining with zircon SHRIMP U-Pb dating of granite intrusions, the authors completed the preliminary research on the collision-closure of the Jinshajiang paleo-oceanic basin. The results show that the emplacement ages of the intrusions in the Jinshanjiang basin are 246.1±3.5 Ma for Tongjige granodioprite in the south (a part of the Jiaren intrusion), 238.1±5.3 Ma, 239.0±5.7 Ma and 227.9±5.1 Ma respectively for Lunong, Linong and Jiangbian granodiorites in the middle, and 213.6±6.9 Ma for the Beiwu granodiorites in the north. Moreover, the collision-closure of the Jinshajiang paleo-oceanic basin progressed gradually from south to north with closure time ranging up to 33 Ma. The collision, however, occurred episodically and collision-closure mainly developed in four periods at around 246 Ma, 239 Ma, 228 Ma and 213 Ma, respectively. The diabases outcropped at Linongdagou as ~222 Ma diabasic dyke—close to the age of the Jiangbian granodiorite, suggesting that local tensional tectonic background occurred in the Jiangbian-Linong area at around 222 Ma. References | Related Articles | Metrics

Select

New evidence for the breakup of the Columbia supercontinent from the northeastern margin of Tarim Craton: rock geochemistry, zircon U-Pb geochronology and Hf-O isotopic compositions of the ca. 1.55 Ga diabase sills in the Kuruktag area. ZHANG Jian,LI Huaikun,ZHANG Chuanlin,TIAN Hui,ZHONG Yan,YE Xiantao 2018, 25(6): 106-123.  DOI: 10.13745/j.esf.sf.2018.11.15 Abstract ( 231 )   PDF (6393KB) ( 454 )   The Mesoproterozoic diabase sills from Kuruktag along the northeastern margin of the Tarim Craton (TC) is of great significance for the understanding of the breakup of the Columbia supercontinent. In this contribution, we report new sensitive high-resolution ion microprobe (SHRIMP) zircon U-Pb ages and in-situ Hf-O isotopes, as well as whole-rock elemental and Sr-Nd isotopic data for the Astingbulake diabase sills. Zircons had high Th/U ratio and banded zoning in cathodoluminescence images, indicating their mafic magmatic origin, and yielded a weighted 207Pb/206Pb age of 1 551±8 Ma and elevated δ18O values of 5.52‰ to 6.53‰ (Gaussian distribution peak at 5.8‰) relative to mantle zircons. Geochemically, the diabase samples are characterized by high FeOT (11.4%13.4%), low TiO2 (1.51%2.45%) and MgO (5.46%7.11%) contents with Mg# ranging from 43 to 52. They contained relatively low REEs contents (90.1116)×10-6 with slightly positive Eu anomalies (δEu=1.051.27). Moreover, these samples are featured by enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILE) and depletion in heavy rare earth elements (HREEs) and Nb-Ta high field strength elements (HFSEs), consistent geochemical features with continental flood basalts (CFB). The coupled whole rock Nd and zircon Hf isotope compositions, with εNd(t) ranging from -3.8 to -1.8 and εHf(t) from -3.7 to 1.9, suggest that the Astingbulake diabase sills derived from enriched continental lithospheric mantle within intra-plate rifting or extensional setting, and the ca. 1.55 Ga diabase is closely related in time to the global early-Mesoproterozoic anorogenic magmatism associated with the breakup of Columbia supercontinent. References | Related Articles | Metrics

Select

Zircon trace elements and their use in probing deep processes. ZHAO Zhidan,LIU Dong,WANG Qing,ZHU Dicheng,DONG Guochen,ZHOU Su,MO Xuanxue 2018, 25(6): 124-135.  DOI: 10.13745/j.esf.sf.2018.11.20 Abstract ( 1161 )   PDF (5880KB) ( 1447 )   Zircon research has been well developed in the past 10 years, from simple U-Pb dating and Hf isotopic analysis to detailed investigation of major and trace elements in various types of zircons. Trace elements in zircons were used not only for estimating magma temperatures by Ti thermometer or identifying rock type and origin, but also for discriminating magmatic, metamorphic and mineralization processes likely controlled by magmatic melts or hydrothermal fluids during zircon crystallization. In this review, we first summarized the major features (texture and trace elemental contents) of magmatic, metamorphic, hydrothermal and detrital zircons. We then carried out a case study on zircons from the post-collisional ultrapotassic rock from southern Tibetan Plateau. We presented the structures, ages and trace elemental characteristics of various types of zircons from ultrapotassic rock and used these zircon characteristics to explain the petrogenesis of ultrapotassic rock, compositions of magma source regions, crustal contamination during magma evolutionary processes, and relationship between lower crust thickening and plateau uplifting. References | Related Articles | Metrics

Select

Petrogenesis of the monzonitic granite of the Qinmalong District, Nanmulin County, Tibet, China. WEI Qirong,ZHAO Shan,WANG Jian,ZHANG Min,XU Huan,OU Bo,XU Changjun,JIN Lei 2018, 25(6): 136-151.  DOI: 10.13745/j.esf.sf.2018.11.9 Abstract ( 138 )   PDF (5061KB) ( 296 )   In this paper, we performed comprehensive analyses on the monzonitic granite outcropped in the Qinmalong District, Nanmulin County, Tibet including field geological survey, petrology, LA-ICP-MS zircon U-Pb dating, elemental and Lu-Hf isotope geochemistry. The results showed that the monzonitic granite from the Qinmalong District belongs to the A-type granite and formed in the Paleogene (E1). The LA-ICP-MS zircon U-Pb age of the granite was 62.0±0.5 to 63.0±0.5 Ma. The weakly peraluminous monzonitic granite formed in high temperature (the saturation temperature of zircon was 745805 ℃, averaged at 766 ℃) and belongs to the high-potassium-calcium-alkaline series. It was enriched in SiO2 (72.6%74.97%), Na2O (2.86%3.59%) and K2O (4.12%5.25%) but depleted in CaO (0.72%1.39%) and MgO (0.26%0.36%). In addition, the granite had high FeOT/MgO value (7.2610.30) and obvious negative Eu anomalies (Eu/Eu*=0.400.70), depleted in Ba, Sr, P and Ti but enriched in Rb, Th, K, Zr and Hf element. The εHf(t) value was -4.7-1.8. The cursts two-stage Hf model age (tDM2) was 1.11.3 Ga. Our study indicates that the A-type granite originates from partial melting of the crustal materials in the Gangdese basement and formed in a tectonic setting of localized stretching in arc environment in response to the subduction and collision between the Indian and Eurasian Plates in the Paleogene. References | Related Articles | Metrics

Select

Geochronology, rock geochemistry and tectonic setting of intermediate-acid intrusive rocks from the Jigongcun molybdenum mining area, Tibet. WANG Jian,WEI Qirong,CI Qiong,ZHENG Qiuping,WANG Xudong,JI Xuefeng,XU Huan 2018, 25(6): 152-164.  DOI: 10.13745/j.esf.sf.2018.11.1 Abstract ( 155 )   PDF (3603KB) ( 315 )   The Jigongcun molybdenum mine is located in the southern part of the GangdiseXiachayu late YanshanHimalaya magmatic arc zone. In this paper, we studied the intermediate-acid rocks widely distributed in the mining area and carried out a systematic investigation on field geological survey, petrology, LA-ICP-MS zircon U-Pb dating and geochemical characteristics of these rocks. The findings indicate that the Jigongcun intermediate-acid rocks are mainly quartz diorite and some granodiorite. The rocks LA-ICP-MS zircon U-Pb age of 51.8±0.5 Ma suggests they were formed in the Eocene (E2) period. They have low K (K2O content ranges 1.66%2.44%) and high Na (Na2O content ranges 3.58%4.06%) contents and belong to calc-alkaline-high potassium calc-alkaline series with quasi-aluminum-weak aluminous characteristics. The ΣREE contents vary greatly (53.6117)×10-6 with light REE enrichment, represented by right-inclined REE distribution mode, and (La/Yb)N value of 3.907.31. No obvious Ce and Eu anomalies were observed (Ce/Ce*=0.921.17; Eu/Eu*=0.961.15), while the trace-element spider diagram shows positive Rb, Th, U and K and negative Ba, Nb, Ta, P and Ti anomalies. The Jigongcun intermediate-acid rocks belong to I-type granite, and formed from the partial melting of the lower basaltic crust due to thickening of the crust, in the subduction and collision environment of the Indo-Eurasian plate. References | Related Articles | Metrics

Select

Petrogenesis of Early Cretaceous volcanic rocks in the Gezhang area, Namling County, Tibet, China. OU Bo,WEI Qirong,XU Huan,WANG Jian,ZHANG Min,XU Changjun,JIN lei 2018, 25(6): 165-181.  DOI: 10.13745/j.esf.sf.2018.11.13 Abstract ( 246 )   PDF (5877KB) ( 253 )   The Gezhang area of Namling County, Tibet is structurally located in the southern part of the middle Gangdese belt (i.e., south-middle Lhasa block) in the Geji-Shenzha back-arc basin. In this paper, we studied the volcanic rocks exposed in the Gezhang area through petrology, LA-ICP-MS zircon U-Pb dating and elemental geochemistry researches and Lu-Hf isotope analysis. The results show that the volcanic rocks in the Gezhang area comprises mainly a set of acidic volcanic clastic rocks and minor volcanic lava. The rock assemblage consists of primarily rhyolitic tuff and ignimbrite (both contain breccia crystal fragments) and small amounts of rhyolite and basalt. Typical magmatic zircon developed in volcanic rocks. Through LA-ICP-MS U-Pb dating of zircons from rhyolite and rhyolitic ignimbrite samples, we obtained rock ages of 133±1.7 Ma and 128±1.5 Ma, confirming the volcanic rocks are formed in the Early Cretaceous (K1). Major elemental analysis shows high SiO2 (69.4%75.8%), K2O (2.93%5.58%) and Al2O3 (12.7%14.6%) and low TiO2 (0.20%0.34%) and Na2O (0.05%2.5%) contents. The volcanic rock is weakly peraluminous to peraluminous (A/NK=0.921.83, A/CNK=1.063.59) and of high potassium calc-alkaline series. The rare earth element (REE) partition mode shows strong light REE-enriched right-sloping type. The (La/Yb)N ratio is 12.3 to 22.0, with obvious Eu negative anomalies (Eu/Eu*=0.470.62). Trace elements generally exhibit positive anomalies of Rb, Th and K, and negative anomalies of Ba, Ta, Nb, Sr, P and Ti. Volcanic rocks have εHf(t) values concentrated between -12.4 and -7.2 and two-stage crust Hf model ages (tDM2) concentrated between 1.5 and 1.7 Ga, equivalent to the geological age of the Nyainqentanglha Group (AnZNq). The Early Cretaceous volcanic rocks in the Gezhang area, therefore, should result from partial melting of the Nyainqentanglha Group (AnZNq) at the base of middle Lhasa block with minor mantle participation, and formed in the continental-margin magmatic arc environment created by the southward subduction of the Bangong-Nujiang plate. References | Related Articles | Metrics

Select

Petrogenesis of the Cuonadong leucogranite in South Tibet: constraints from bulk-rock geochemistry and zircon U-Pb dating. HUANG Chunmei,LI Guangming,ZHANG Zhi,LIANG Wei,HUANG Yong,ZHANG Linkui,FU Jiangang 2018, 25(6): 182-195.  DOI: 10.13745/j.esf.sf.2018.11.2 Abstract ( 295 )   PDF (3155KB) ( 397 )   Leucogranite is one of the mineral components of the Cuonadong dome core located in the eastern part of the Himalayan orogenic belt. LA-ICP-MS zircon U-Pb dating yielded crystallization ages of 20.6±0.3 Ma and 16.7±0.2 Ma for two-mica and garnet-bearing muscovite granites, respectively, in accordance with the Miocene Himalayan leucogranites. The characteristics of both leucogranites feature high SiO2 (71.6%74.6%), Al2O3 (14.5%16.1%), and K2O (4%4.7%) contents with A/CNK of 1.161.22, suggesting the leucogranites belong to high-K calc-alkaline and strongly peraluminous granites that are enriched in Rb, U, K, and Pb and relative depleted in Nb, Ta, Zr and Ti. Garnet-bearing muscovite granites have strong negative Eu anomalies (Eu/Eu* between 0.29 and 0.46), while relatively weak negative Eu anomalies (Eu/Eu* between 0.58 and 0.80) were found in two-mica granites. Two-mica granites have Rb/Sr ratios of 2.43.5, Ba contents of (200253)×10-6, and relatively low TiO2 contents, likely formed from muscovite dehydration melting of metapelites under the decompression condition caused by the movement of the STDS. Garnet-bearing muscovite granites, on the other hand, show non-chondritic anomalies in K/Rb, Zr/Hf, Nb/Ta and Y/Ho ratios, REE tetrad effects, and abnormally high Rb/Sr ratios (18.622.2)—all features of highly evolved granites favoring mineralization of rare metal elements such as W, Sn, Be, etc. Meanwhile, garnet-bearing muscovite granite pluton is adjacent to the W-Sn-Be ore deposits within the Cuonadong dome, raising the likelihood that the occurrence of the garnet-bearing muscovite granite might contribute to W-Sn-Be mineralization. Likewise, common spatiotemporal patterns are shared by two-mica granites and Zhaxikang Pb-Zn deposits, an indication that a genesis relationship may exist between the two. Related Articles | Metrics

Select

The source of primitive magma for the Jinbaoshan PGE-rich intrusion, western Yunnan: constraints from PGE contents and Sr-Nd isotopes. LU Yiguan,HE Wenyan 2018, 25(6): 196-208.  DOI: 10.13745/j.esf.sf.2018.11.3 Abstract ( 144 )   PDF (5076KB) ( 252 )   The Jinbaoshan complex is located in the west margin of the Yangtze Plate, adjacent to the northern part of the Ailaoshan orogenic belt. It contains abundant Pt-Pd resources and is a large magmatic PGE deposit in the Emeishan Large Igneous Province (ELIP). The complex is mainly composed of wehrlites with ore body presented as stratoid or lentoid in wehrlites. Mantle is the most important source of forming the Ni and PGE deposits, thus the study of Ni, Cu and PGE geochemical behavior is important for understanding the genesis of magmatic Ni-Cu-PGE deposits. In this work we determined the PGE and Sr-Nd isotope contents in wehrlites from the Jinbaoshan intrusion. Combined with PGE studies on different series of rocks in the ELIP and research on the Dsul/sil for Ni, Cu and PGE by previous researchers, we suggest that the primitive magma is formed by moderate to high degrees of melting (25%40%), resulting in 12.8 ppb Pd, 9.8 ppb Pt, 0.6 ppb Rh, and 0.7 ppb Ir, close to the contents of the ELIP picrite. The Jinbaoshan intrusion has experienced 10%20% crustal contamination from the Yangtze upper crust during magma evolution. Based on the batch partial melting formula and Dmineral/melt parameters for the PGE, the PGE contents of Jinbaoshan mantle were calculated to be 5.3×10-9 Pd, 7.5×10-9 Pt, 0.75×10-9 Rh, and 1.5×10-9 Ir. Compared to primitive mantle, the mantle of the Jinbaoshan intrusion does not show obvious PGE enrichment. Therefore we may conclude that a large magmatic PGE deposit could be formed by moderate to high degrees of mantle melting accompanied by large scale mixing of magma and sulfides. References | Related Articles | Metrics

Select

Magma mixing of the Daocheng batholith of western Sichuan: mineralogical evidences. ZHANG Ruigang,HE Wenyan,GAO Xue,LI Mengmeng 2018, 25(6): 226-239.  DOI: 10.13745/j.esf.sf.2018.11.4 Abstract ( 226 )   PDF (3775KB) ( 304 )   The Yidun arc, located between the Songpan-Garze Terrane and Qiangtang Block of southwestern China, was formed in response to the Late Triassic large-scale subduction orogenic process. The Daocheng batholith consists of granite, granodiorite and K-feldspar granite. Abundant massive mafic microgranular enclaves (MMEs) developed mainly within the granodiorite and K-feldspar granite, forming clear contacts with the host granites. The MMEs are characterized by the quartz eye structure, quenched apatite, and plagioclases phenocrysts with obvious oscillatory zones. Based on the systematic petrographical, mineralogical and geochemical characteristics of plagioclase, hornblende and biotite from the host rock and MMEs of the Daocheng batholith of western Sichuan, we provide here not only the constraints on the physicochemical conditions for mineral and host rock formation, but also important insights into understanding the magma mixing process and structural setting. Our study shows that the plagioclases in the granodiorite and MMEs are all dominated by andesine with rounded or embayed cores. In the former, the An contents in the cores vary between 21 and 50, significantly higher than the An contents in the mantles (2134), and in the latter, the An contents (2944) are waved and concentrated in the mutation annulus. The overlap of An value between MMEs and host granite diorite indicates that magma mixing occurred during their formation. The An contents increase with the increase of Al2O3, FeO, MgO and CaO, but decrease with the increase of SiO2, Na2O and K2O. The hornblendes from the host rock and MMEs are rich in Mg and Fe, with CaB and Ti values of 1.561.75 and 0.080.13, respectively. They both belong to the calc-amphiboles, crystallized at 697725 ℃ and 680705 ℃, respectively. The biotites of granodiorite are enriched in iron, depleted in calcium and magnesium, which belongs to typical magmatic biotite. These biotites have Mg/(Mg+Fe2+) ratios of 0.370.45, TiO2 contents of 3.54%4.62%, oxidation coefficient of 0.080.11, Mg# values of 0.390.46, MF values of 0.360.44, AlⅥ value (molecular number of cations in one unit) of 0.030.11. The biotites from granodiorite display low CaO, MgO and AlⅥ values and high FeO and TiO2 contents, and were most likely crystallized between 584 ℃ and 624 ℃ as calculated by the cation numbers of Ti and Al. According to the tectonic setting discrimination diagrams and the geochemical features of biotites, we conclude that the Daocheng granodiorite belongs to the I-type granitederived from the partial melting of the Late Triassic arc lower crust with minor mantle-derived materials, and the MMEs were generated by the mixing of mafic and felsic magma. References | Related Articles | Metrics

Select

Late Jurassic adakitic granites in northeastern Xingan block: geochronology and geochemical characteristics and tectonic significance. ZHAO Yuandong,CHE Jiying,XU Fengming,ZHU Qun,WANG Kuiliang 2018, 25(6): 240-253.  DOI: 10.13745/j.esf.sf.2018.11.18 Abstract ( 197 )   PDF (5326KB) ( 267 )   Although intense Mesozoic magmatism widely occurred in the Great Hinggan Range and is a hot topic in tectonic research, reports on the Late Jurassic granites is scarce. In this paper, we present three new LA-ICP-MS zircon U-Pb ages 158.5±1.6 Ma, 156.1±0.59 Ma and 154.1±1.1 Ma for granite outcrop in northeastern Xingan block to confirm that the granite emplacement occurred in the late Jurassic, not the early Mesozoic. These Late Jurassic granites are composed of medium coarse-grained granodiorite and monzonitic granite. Petrochemically they belong to peraluminous and high-K calc-alkaline series with high Si, K, Na and Al contents and low Fe, Mg and Ti contents. They are enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE, e.g. Rb, Ba, Th, U, Sr), depleted in heavy rare earth elements (HREE), Y and high field strength elements (HFSE, e.g. Nb, Ta, Zr, Hf), with high La/Yb, Sr/Y ratios and possibly belong to “C-type” adakites. Genetics of the granite is closely related to the continental collision orogeny caused by the closure of the Mongol-Okhotsk ocean. The magma originated from the partial melting of basic rocks of the thickened lower crust under the orogenic belt with the addition of rich Al crustal material during magmatic evolution. The difference between the Late Jurrasic adakitic and adjacent Early-Middle Jurassic TTG granites reflects the tectonic evolution of the Mongol-Okhotsk ocean from subduction to continental collision during the Jurassic. References | Related Articles | Metrics

Select

Geochemical characteristics, Sr-Nd Isotopic compositions and geological implications of metamorphic basalts from the Guishan complex in the Xinyang area, Henan Province. CHANG Qingsong,LI Chengdong,ZHAO Ligang,XU Yawen,WANG Shiyan 2018, 25(6): 254-263.  DOI: 10.13745/j.esf.sf.2018.9.5 Abstract ( 473 )   PDF (5021KB) ( 309 )   In this report, we present the geochemical characteristics and Sr-Nd isotopic compositions of Neoproterozoic metamorphic basalts from the Guishan complex in the Xinyang area, south of the Shang-Dan Fault. All basalt samples analyzed belonged to the sub-alkaline tholeiitic basaltic series and could be classified into high-Ti and low-Ti types. The low-Ti type basalts had higher Mg content, low degrees of LREE/HREE fractionation and enrichment of incompatible elements, and relatively enriched Sr-Nd isotopes, showing E-MORB characteristics. The high-Ti type basalts had higher Fe content, high degrees of LREE/HREE fractionation and enrichment of incompatible elements, and relatively depleted Sr-Nd isotopes—compatible with OIB features. The low-Ti type basalts might result from the partial melting of lithospheric mantle caused by a mantle plume, with some crustal contamination. The high-Ti type basalts, on the other hand, might be generated from the partial melting of a mantle plume with minor crustal influence. The geochemical discriminant diagrams of tectonic setting show that the metamorphic basalts erupted in the extensional mantle-plume environment, possibly as part of the Meso-Neoproterozoic magmatic activities in the extensional environment of the Shang-Dan Fault. References | Related Articles | Metrics

Select

Zircon U-Pb chronology, Hf isotopic compositions, geochemistry characteristics and geological significance of Shouwangfen complex in Yanshan region. DONG Pengsheng,DONG Guochen,SUN Zhuanrong,LI Huawei,WANG Shushu,WANG Weiqing,GENG Jianzhen 2018, 25(6): 264-276.  DOI: 10.13745/j.esf.sf.2018.9.9 Abstract ( 174 )   PDF (3714KB) ( 256 )   The Shouwangfen complex is composed of biotite quartz diorite and quartz monzonite. Our LA-ICP-MS zircon U-Pb chronological study shows the quartz diorite and quartz monzonite ages are 128±1 Ma, suggesting the Shouwangfen complex formed in the Early Cretaceous, closely coincides with the period of large-scale magmatic activity in the eastern North China Craton. The Shouwangfen complex belongs to the quasi-aluminous rock of alkaline series (A/CNK ranged 0.690.89, A/NK ranged 1.191.35, Na2O+K2O ranged 8.48%9.06% and K2O ranged 3.874.96%), enriched in Rb, Ba and Sr and depleted in Nb, Ta, Th and P. It has the characteristics of high Sr ((6841018)×10-6) and Ba ((11631506)×10-6) contents, high Sr/Y(43102) and La/Yb (3191) values, low Y ((7.1916.55)×10-6) and Yb ((0.471.28)×10-6) contents, enrichment of light rare-earth element (LREE), and no Eu anomalies. The quartz diorite and quartz monzonite have low εHf(t) values of -18.1 to -11.1 and -18.6 to -13.2, respectively. Geochemical characteristics indicate the Shouwangfen complex formed under the tectonic setting of extension environment created by the ancient Pacific plate subduction to the Eurasian continent. The complex originated from the partial melting of Paleoproterozoic crustal material with varying contributions from enriched mantle. The high Sr/Y value, however, is not a source feature due to its positive correlation with SiO2, but a result of fractionation during emplacement. References | Related Articles | Metrics

Select

Fluid Earth Science and Earth System Science. LUO Zhaohua 2018, 25(6): 277-282.  DOI: 10.13745/j.esf.sf.2018.11.17 Abstract ( 382 )   PDF (1210KB) ( 739 )   In recent years, Earth System Science (ESS) gradually becomes the new trend of the Earth Science. However, Solid Earth Science (SES) has hardly merged with it. This is because ESS is the application of system- or complex-science to the Earth Science, while SES is essentially a category of pure Earth Science, in which linear Earth processes are mainly concerned, or non-linear Earth processes are researched using pure Earth science approaches. Fluid Earth Science (FES), on the other hand, not only encompasses studies of the fluid system of the Earth, but also the strong and weak interactions between fluid and solid systems. Consequently, only FES can mediate the integration of SES into ESS. References | Related Articles | Metrics

Select

Fluid minerals, mineral assemblages, fluid rocks: significance in the studies of rocks and ore deposits. SU Shangguo,CUI Xiaoliang,LUO Zhaohua,JIAN Dongchuan,HOU Jianguang,NING Yage,LIU Lulu,ZHANG Bo,LIU Meiyu,JIANG Junyi,GU Dapeng,HUO Yanan 2018, 25(6): 283-289.  DOI: 10.13745/j.esf.sf.2018.11.6 Abstract ( 183 )   PDF (2367KB) ( 373 )   Fluids play a key role in the origin of rocks and ore deposits. They are the connecting media for the interaction between different Earth layers. Currently in fluid research, most geologists mainly study fluid alteration of existing minerals and rocks while a few geologists pay attention to minerals crystallized from fluids. In this paper, we present the definition and characteristics of fluid minerals, mineral assemblage and fluid rocks based on many years of research. Our recent study shows that magma may contain large amounts of fluids, originated from fluid concentration during magma evolution, magma-country rock interaction or external sources. Putting forth the concept of fluid mineral shall deepen our understanding of geologic processes hence develop new frontiers in petrologic and ore deposit research. The concept can be useful in mineral exploration and metallogenic prediction. References | Related Articles | Metrics

Select

Research on the current status and future of U-Pb chronology study of uranium minerals from the sandstone-type uranium deposits. ZHOU Hongying,TU Jiarun,LI Guozhan,XIAO Zhibin,GENG Jianzhen,GUO Hu,YE Lijuan,XU Yawen,ZHANG Jian,LI Huimin 2018, 25(6): 290-295.  DOI: 10.13745/j.esf.sf.2018.11.5 Abstract ( 168 )   PDF (887KB) ( 347 )   In recent years we have conducted in-depth studies on the genetic mineralogy and U-Pb geochronology of uranium minerals (uraninite, coffinite, brannerite, etc.) and U-bearing minerals (rutile, apatite, etc.) from sandstone-type uranium deposit, using jointly secondary ion mass spectrometry, laser ablation multi-collector inductively coupled plasma mass spectrometry, electron probe microanalysis and isotope dilution-thermal ionization mass spectrometry. New methods of U-Pb isotopic dating for uranium minerals, however, should be tested and established in order to acquire accurate formation time for rocks and minerals from sandstone-type uranium deposit. Such knowledge is important for a comprehensive and accurate understanding of the formation and evolutionary history of the sandstone-type uranium deposit and for developing a new mineralization theory for sandstone-type uranium deposit. The new isotopic dating methodology will also have a broad application in uranium geological exploration. References | Related Articles | Metrics

Select

Discussions on crust-mantle structure during the formation of Yanshanian of large-super large scale deposits in the Jiaodong Gold Ore District: constraints from ore-forming igneous assemblage. Earth Science Frontiers, 2018, 25(6): 296-307 LIU Cui,DENG Jinfu,LI Shengrong,XIAO Qinghui,JIN Tianjie,SUN Hao,DI Yongjun,LIU Yong,ZHAO Guochun 2018, 25(6): 296-307.  DOI: 10.13745/j.esf.sf.2018.11.16 Abstract ( 185 )   PDF (2832KB) ( 381 )   The deep material composition and crust-mantle structure when large-super large scale metal deposits are forming have always been the focus of research and challenging pursues. The Jiaodong Gold Ore District developed many Yanshanian large-super large scale gold deposits. Based on plate tectonic theory and through examination of regional and ore-forming igneous assemblages and their characterics, the authors discuss in this paper the material composition in earths depth and crust-mantle structure during the gold forming period. The regional igneous assemblages prior to ore forming period are mainly granodiorite-granite(G1G2 suites) and some tonalite-trondhjemite (TT suites) assemblages. The volcanic rock assemblages of the Qingshan Formation are basaltic andesite-andesite-dacite-rhyolite-trachyteandesite-shoshonite-trachyte assemblages, which include high Mg andesite (HMA) and Mg andesite (MA). The ore forming igneous assemblages in the district are wide-spectrum dyke swarm (WSDS) of basic to acid igneous rocks, which include high Mg dirorite (HMgδ) and Mg dirorite (Mgδ). The above-mentioned igneous assemblages and the special igneous rocks of the TTG1, HMA, MA, HMgδ and Mgδ are igneous assemblages of arc setting and have the corresponding characteristics. Therefore they were formed in oceanic subduction environment and have the corresponding crust-mantle structure and material composition. These igneous rocks came from partial melting of different parts of subduction belt, including oceanic crust, mantle wedge and continental crust, revealing a hot crust-mantle structure during the Yanshan era. Both ore-forming igneous and gold metallogenic events resulted from large-scale intrusive magmatic activity of crust (or crust-mantle). References | Related Articles | Metrics

Select

The Yinachang deposit in central Yunnan Province, Southwest China: A “Bayan Obo-type” Fe-Cu-REE deposit. WEN Ligang,ZENG Pusheng,ZHAN Xiuchun,FAN Chenzi,SUN Dongyang,WANG Guang,YUAN Jihai,FEI Xiaojie 2018, 25(6): 308-329.  DOI: 10.13745/j.esf.sf.2018.9.3 Abstract ( 394 )   PDF (3906KB) ( 646 )   The Yinachang Fe-Cu-REE deposit is one of representative Proterozoic Fe-Cu-REE deposits in central Yunnan, SW China. Besides Fe and Cu, rare-earth elements (REEs, mainly La, Ce), Nb, Y, Mo and Co coexist in the deposit. Study has shown that REE contents are relatively high in both banded and vein ores ranging in (1446.8311259.23)×10-6 and (2020.923415.51)×10-6, respectively, with light REEs (e.g., La, Ce) especially enriched. Also, the content of rare element Nb reaches up to (278.8529.0)×10-6 in the banded ores. However, it has long been difficult to study mineral characteristics, especially occurrence characteristics, of rare and rare-earth minerals using traditional testing techniques, which were inadequate to identify these minerals due to complex mineral composition of ore deposit and relatively low mineral contents in ores. In this study, we used automated mineral identification and characterization system (AMICS)—the most up-to-date mineral automatic analysis system in mineralogy and geology in the world, combined with scanning electron microscope and X-ray energy dispersive spectrometer (SEM-EDS) microstructural in-situ analysis technique, to complete quantitative mineral identification in the Yinachang Fe-Cu-REE deposit, an undertaking unattainable by conventional means of rock-mineral identification. The results demonstrate that the deposit contains large quantities of parisites and bastnaesites and small quantities of monazites, allanites, columbites, fergusonites, yttrialites and Nb-bearing rutiles. Bastnaesites, monazites, columbite and fergusonite are mainly concentrated in the banded ores and closely associated with iron oxide minerals (magnetites), siderites, apatites, flourite and early sulfides such as chalcopyrite, pyrite, etc, while parisites, allanite, yttrialite and Nb-bearing rutile are enriched in vein ores coexisting mainly with chlorites, calcite, quartz and late sulfides such as chalcopyrite, pyrite, etc. Plainly, both iron oxide and copper sulfide mineralization stages are associated with REE mineralization. We identified two main mineralization stages, i.e., iron oxide-apatite-REE (Ⅱ-1) and Cu sulfides(-Au)-REE (Ⅱ-2) mineralization stages, both were apparently related to the deep (mantle) magmatic activities: bastnaesites, monazites, columbite and fergusonite primarily formed in the Ⅱ-1 stage, likely during the breakup of the Columbia supercontinent; and parisites, allanite, yttrialite and Nb-bearing rutile mainly formed in the Ⅱ-2 stage, possibly during the breakup of the Rodinia supercontinent. Through comparative studies, we found that the Yinachang Fe-Cu-REE and giant Bayan Obo Nb-Fe-REE deposits are comparable in tectonic settings, metallogenic element assembles, ore-hosting rock series, mineral compositions, ore-forming ages and material sources. Therefore, we propose, preliminarily, that the Yinachang Fe-Cu-REE deposit is a “Bayan Obo-type” deposit. References | Related Articles | Metrics

Select

Apatite fission track analysis of tectonic activity in the Dongshangen mining area, East Kunlun, QinghaiTibet Plateau. CHEN Xue,YUAN Wanming,YUAN Erjun,WANG Ke,FENG Zirui 2018, 25(6): 330-337.  DOI: 10.13745/j.esf.yx.2018.9.50 Abstract ( 132 )   PDF (2901KB) ( 257 )   Through the analysis of seven apatite samples collected from the Dongshangen mining area of east Kunlun Mountain, Qinghai Province, we showed that the apatite fission track ages vary from 136 to 67 Ma. The ages can be divided into three groups of 136112, 10195 and 7467 Ma to better reflect the uplifting and exhumation events occurred in this region. The thermal history of the Dongshangen mining area are delineated into four stages by fission track modeling. The first stage (160120 Ma) corresponds to the compressive movement of both the Qiangtang and Lhasa blocks towards the Eurasian Plate. The second stage (12015 Ma) coincides with the Aerjin fault strike-slip, the northern Tibetan Plateau uplifting and the northward subduction movement of the Gangdese block in the Late Yanshan period. This stage experienced rapid cooling and uplifting until the end of the Early Cretaceous. In the third stage (8023 Ma) the region was relatively stable, cooling down slowly, while the fourth stage (23 Ma to present) undergoes rapid cooling and uplifting, corresponding to the collision of the Indian Plate towards the Eurasian Plate. References | Related Articles | Metrics