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Pondering over the genesis of rocks and the evolution of lithosphere. Chen Guoneng 2011, 18(1): 1-8.  Abstract ( 7170 )   PDF (25443KB) ( 75027 )   Variation of intrinsic energy of the lithosphere results in forming and perishing of rocks. Evolution of the three kinds of rocks that constitute the lithosphere produces different tectonic effects on the earth surface, and the evolutional effects on the oceanic and continental crusts are found with complementing relationship: increasing intrinsic energy in the oceanic lithosphere leads to the birth of rocks, otherwise to the perish; and in the continental lithosphere, increasing intrinsic energy leads to the perish of rocks, otherwise to the birth. The former process creates a rocksequence in which the rocks become older from the mid oceanic ridge outwards either on a horizontal plane or on a vertical section, and the latter produces a rocksequence in which the rocks become younger from the core of a continent outwards on a horizontal plane and become younger from the MI upwards and downwards on a vertical section. Related Articles | Metrics

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A comparison between the Late Mesozoic DabieSulu orogenic belt and South China in terms of their granite spatialtemporal distributions and stress fields. DING Ru-Xin, ZHOU Jie-Yi 2011, 18(1): 9-14.  Abstract ( 4333 )   PDF (1326KB) ( 4635 )   The insitu remelting theory of granite opens a new perspective for the study of the tectonic cause of the spatial and temporal distribution of the Late Mesozoic (Late JurassicEarly Cretaceous) granite in South China. By comparison, we found that there is a high degree of similarity and consistency in the spatial and temporal distribution of granite and the stress field in the Late Mesozoic between the DabieSulu orogenic belt and its north vicinity (especially the Sulu orogenic belt and its north vicinity) and South China. That is, the granite distribution is mainly along the NE direction, turns from old to new from NW to SE, and is under the control of the same stress field caused by the highspeed subduction of the paleoPacific plate towards the Eurasia continent. On the basis of this theory, we may conclude that the Late Mesozoic (Late JurassicEarly Cretaceous) granite of the DabieSulu orogenic belt and its north vicinity and the Late Mesozoic (Late JurassicEarly Cretaceous) granite of South China were very likely formed by the same event, that is, the subduction of the paleoPacific plate towards the Eurasia continent. The linkage effects between the plates caused by the subduction of the paleoPacific plate led to the friction between the South China plate and the North China plate, and as a result, the temperature of the crust increased and the granite magma layer formed. With the change of subduction speed, the position of the granite remelting interface moved and thus brought about the tendency that the Late Mesozoic granite became newer from NW to SE (at least the Sulu orogenic belt seems to be like this). Related Articles | Metrics

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Timespace distribution and formation mechanism of the Mesozoic mafic dikes in Southeast China. 2011, 18(1): 15-23.  Abstract ( 6819 )   PDF (14024KB) ( 20642 )   Mafic dikes are found forming in different periods of the Mesozoic in Southeast China. Ages of the dikes show a spatial variation as that of the Mesozoic granites of this area, i.e. becoming younger from inland to coastal region, but the activityfastigia of mafic dikes and granites are not synchronous, and that of the former occurred relatively behind. Mafic dikes usually occurred limited in tensional cracks developed within granite bodies, seldom to perforate into the fractures in the country rocks of granite bodies. The mafic dikes generally occurred within the corresponding mafic volcanic belt that was located on the west of the intermediatedacid eruption belt of the same time, indicating that the mafic magma of eruption and intrusion should have been derived from the same source, i.e., the bottom part of the crustal magma layer or the mantle melt layer. Both reducing scales of the intermediatedacid eruption and the seaward migration of mafic eruption and intrusion belts after the Late Jurassic suggest decreasing crustal temperature of this area in the Late Mesozoic. Related Articles | Metrics

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The relationship between evolution of the intracrustal magma layer and development of basins: An example from the Mesozoic basins in Southeast China. 2011, 18(1): 24-31.  Abstract ( 1798 )   PDF (5264KB) ( 1855 )   Three different types of structural basins, i.e. downwarping, faulting and faultingblock basins were developed in the Mesozoic in Southeast China. The first type formed from the Late Triassic to the Early Jurassic with coalbearing strata; the second formed from the Middle Jurassic to the Early Cretaceous with volcanic strata; and the last from the Cretaceous to the Paleogene time with continental redbed. The formation of the three types of basins was closely related to the evolution of the Mesozoic intracrustal magma layer of this area. Subduction of the paleoPacific plate initiated at the Late Paleozoic increased the intrinsic energy of the lithosphere of this area, caused the formation and thickening of the intracrustal magma layer, brought on bendingdeformation of the cover over the magma layer, and thus resulted in the formation of numerous downwarping basins in the earlier Mesozoic. Multicrustal movements from the Indosinian to the Early Yanshanian period broke the crust and formed lots of faults that provided conduits for magma eruption and thus formed a series of volcanic basins controlled by faults in the eastern coastal area where the MI (Melting Interface understood as the upper face of the intracrustal magma layer) was imbeded relatively shallow. Decreasing intrinsic energy of the crustal melting system started at the end of the Late Jurassic and made the crust cool down and shrink, which resulted in faultblock movements under gravitation and thus produced lots of faultblock basins in the Late Mesozoic and the Early Cenozoic. Related Articles | Metrics

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Mechanism of the Cenozoic tectogeomorphologic evolution in the Southeast China continental margin. 2011, 18(1): 32-38.  Abstract ( 1836 )   PDF (2831KB) ( 3989 )    From the Mesozoic Andean continental margin to the presentday arcbasin system, the evolution of landform of Southeast China continental margin underwent three stages, i.e., Palaeocathysian mountains at the end of the Cretaceous, peneplain in the late Paleogene, and seabasins in the Neogene. Leveling of the Palaeocathysian mountains reduced the crustal thickness and thus decreased the imbedding depths of the Moho and increased the bouguer gravity. On the other hand, descending crustal temperature resulted in both the crystallizing of the Mesozoic crustal melting layer and the cutting down of the faults over the layer. Coupling of the above factors led to the downward movement of faultblocks in a large scale initiated in the Miocene along with development of the normal fault system in the seabasin, eruption of basaltic magma, lowering position of the Moho, and formation of the islandarc and blockmountains on the both sides of the subsiding region. Related Articles | Metrics

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Formation mechanism of the Guidong CGB in North Guangdong and the evolution of melting interfaces. 2011, 18(1): 39-48.  Abstract ( 2248 )   PDF (6700KB) ( 999 )   Reencoding of the geological and geochemical data concerning the Guidong Composite Granite Body(CGB) with the hypothesis of insitu melting and crustal convection suggests that the Guidong CGB was formed by repeated crustal melting of this area in the Mesozoic. On that basis, this paper rebuilds the melting interface(MI) formed in different Yanshanian periods: the MI formed in the Early Jurassic totally tilts from south to north, which resulted in the early Yanshanian granite cropping out from inner facies to transitional facies and to margin facies from south to north on the presentday denudation plane; the MI formed in the melting event of the Late Jurassic totally tilts from north to south, and the distribution of granite bodies formed in this period was basically limited within the old member of the Guidong CGB thus usually more acid than the old one; the melting event of the Early Cretaceous produced a southward tilting MI and formed two kinds of rocks, quartz syenite and subdaciteporphyry. Difference of the rocks is likely concerning with the source rocks involved into the melting event. Metallogenic prediction on the above model in the Xiazhuang orefield, eastern Guidong CGB, has been approved by drillings to a certain extent. Related Articles | Metrics

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Geological and geochemical evidences for insitu melting origin of the Xilingang granite in Guangdong Province. 2011, 18(1): 49-55.  Abstract ( 2395 )   PDF (19464KB) ( 1884 )    Lots of information concerning granite genesis can be obtained from the geological sections of Xilingang granite body in Guangdong Province. The sections indicate that the Baihedong Formation (K1bh) formed in the Early Cretaceous acted as a residual cap over the Xilingang granite body with abrupt contact in between. The granite underlying the contact contains numerous red bed clastics that reduce gradually with increasing depth in the rock body. The results of geochemical and mineralogical analysis suggested that materials of granite were from the insitu rockstrata including part of the red bed of Baihedong Formation. Differentiation during the meltingcrystallizing process led different elements to be enriched in different depths of the rock body. Growth of quartz crystals of granite is found in a stable environment and during crystallization of quartz, SiO2 supersaturation of magma gradually decreases. All the above data indicate that the Xilingang granite was formed by insitu melting of the crustal rocks, not the intrusion from a depth source. Related Articles | Metrics

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The ordering mode of geochemical differentiation index of elements in continental crust. 2011, 18(1): 56-62.  Abstract ( 2069 )   PDF (1130KB) ( 2398 )    This paper analyzes the compatibility of elements and the correlation between element partition coefficient in two phases and geochemical differentiation of elements in crust and mantle. On the basis of predecessors research, a geochemical differentiation model of elements in crust and mantle is developed, and the relationship between enrichment mechanism of numerous incompatible elements in the crust and the process of partial melting of rocks is proposed. We collected and collated average chemical composition of 60 kinds of elements in primary mantle and every layer of crust. On the basis of the theoretical model of geochemical differentiation of elements in crust and mantle, we have calculated the differentiation intensity index and analyzed its relation to the compatibility. Logarithm values of these indexes are arranged from high to low to make up a sequence of geochemical differentiation intensity of elements in the upper crust: at the left side of the sequence are strongly positive differentiation elements, namely strongly incompatible elements, enriched in the continental crust; at the right are strongly negative differentiation elements, namely strongly compatible elements, relatively depleted in the continental upper crust; the enrichment or depletion of elements whose differentiation index value are close to 1 is not obvious in the crust and they are called transition elements. According to this sequence, we propose a new geochemical classification of elements: strongly positive differentiation elements distributed in the left of the sequence are crustphilic; strongly negative differentiation elements distributed in the right of the sequence are mantlephilic; elements located in the middle of the sequence are crustphilicmantlephilic transition elements. The element positions and the law of their distribution in the periodic table of elements according to above categories, the variation of differentiation intensity index and its relationship with the properties of corresponding elements in the periodic table of elements are analyzed in this paper. Related Articles | Metrics

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A study of mineral composition and microtexture of the mafic microgranular enclave in granites in SE China. 2011, 18(1): 63-73.  Abstract ( 4753 )   PDF (5747KB) ( 5595 )    Observations of mineral composition and microtexture of the mafic microgranular enclaves (MMEs) from different granite bodies in SE China demonstrated that no matter what mineral, rockforming or accessory, two generations of the mineral were found coexisting in all samples of the MMEs. Most of the MMEs were not with igneous texture, as they were generally considered, but with the melting texture. Multitypes of textures coexisted in the same enclave suggested that the MMEs should have been derived from the residues of partial melting of rocks. Differences of mineral composition and microtexture between MMEs or between core and rim of one MME suggested a varying melting degree of source rocks, implying that the MMEs were in different evolution stages in magma. Related Articles | Metrics

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Genesis of mafic microgranular enclaves in granites in SE China. 2011, 18(1): 74-81.  Abstract ( 4147 )   PDF (3414KB) ( 4178 )   Combing the field investigation of mafic microgranular enclaves (MMEs) in granites and the studies of geometry, mineralogy, microtexture and petrochemistry of enclaves, we advanced a model of evolution of MMEs and their relationship to the development of restites produced by partial melting of rockblocks during the insitu melting process. The model reveals that the xenoliths are the precursors of MMEs, and that the xenoliths are the rockblocks coming into the magma from the cover of the magma layer during the melting and the MMEs are the mafic restites of the xenoliths. Variations in type, shape and maficity of MMEs reflect different melting degrees of rockblocks. Biotiterich enclaves are the final products of restite development, which will mix with the host granite magma in further melting, marking the end of the process from rockblock to granite magma. Related Articles | Metrics

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Genesis of mafic microgranular enclaves in granites in SE China. 2011, 18(1): 82-88.  Abstract ( 1894 )   PDF (3968KB) ( 2469 )   Combing the field investigation of mafic microgranular enclaves (MMEs) in granites and the studies of geometry, mineralogy, microtexture and petrochemistry of enclaves, we advanced a model of evolution of MMEs and their relationship to the development of restites produced by partial melting of rockblocks during the insitu melting process. The model reveals that the xenoliths are the precursors of MMEs, and that the xenoliths are the rockblocks coming into the magma from the cover of the magma layer during the melting and the MMEs are the mafic restites of the xenoliths. Variations in type, shape and maficity of MMEs reflect different melting degrees of rockblocks. Biotiterich enclaves are the final products of restite development, which will mix with the host granite magma in further melting, marking the end of the process from rockblock to granite magma. Related Articles | Metrics

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Ionic structure of oreforming elements and their behaviors in mineralization related to granite formation. 2011, 18(1): 89-94.  Abstract ( 1813 )   PDF (3845KB) ( 2083 )    Oreforming elements related to formation of different types of rocks are found with different kinds of ionic structures: those with the inertgaseous ionic structures generally enriched in the formation of sedimentary rocks, while those with the transitional or cupreous ionic structure are affinitive with the formation of magmatic rocks. Further researches indicate that various elements involved in the rock melting process are redistributed within and over the continental crust during the crystallization of crustal magma layer: the lithophile elements held the position of magma layer while the sulphophile elements moved to the cover of the layer, and the hydrophile elements migrated to hydrosphere while the atmophile elements to the atmosphere. Consistency of geological and geochemical structures of continental crust illustrated by the above processes reveals the unity between the microcosm and macrocosm of the natural world. Related Articles | Metrics

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Metallogenesis of subgroup elements and related ore fields.  2011, 18(1): 95-101.  Abstract ( 3879 )   PDF (15551KB) ( 7198 )   Insitu melting (remelting) not only results in formation of granite, but also in enrichment of subgroup elements to form different types of oredeposits. The subgroup elements include oxyphiles and sulphophiles, and thus the related orefield can be divided into three types, i.e. of oxyphiles, of sulfophiles and of both composited. The first type that occurred in granite body with the ages similar to that of the host rock is controlled by magmatic differentiation and its appearance depends on the erosion depth of the rockbody. The occurrence of the second type generally with different distance from the source granite body is controlled by both the depth of protuberant magma interface (MI) and the attitude of orecontrolled structure. The formation of the third type is related to multiple melting (remelting), which is characterized by oxyphile (especially uranium) oredeposit within granite and oredeposit of sulfophiles in the surrounding of the rock body. Related Articles | Metrics

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Metallogenetic zonation and exploring direction of oredeposits in the ChangkengChashan orefield, Guangdong Province. 2011, 18(1): 102-109.  Abstract ( 2586 )   PDF (25211KB) ( 1416 )   Among the 17 endogenic metallic oredeposits (prospects) in the ChangkengChashan orefield, central Guangdong Province, we selected three deposits, i.e. the Changkeng AuAg deposit, the Hengjiang and the Chashan polymetallic deposits, respectively in the north, middle and south of the orefield, as the examples for the research of metallogenetic zonation. The results show that though the three deposits have different locations, scopes and oreforming elements, they all have the same metallogenetic zonation as Cu→Zn→Pb→Ag→Au from the bottom upwards of an ore body. Further study on the above basis indicates that all the deposits (prospects) as a whole in the orefield surrounding two granite bodies, of which one outcrops and one is concealed, exhibit the same metallogenetic zonation as that of a single deposit. The above findings would be helpful for the exploration in this area. Related Articles | Metrics

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The relationship between granite evolution and uraniumthorium enrichment: An example from the Guidong granite body, North Guangdong Province. 2011, 18(1): 110-117.  Abstract ( 4255 )   PDF (31677KB) ( 7516 )   The study of variations of uranium and thorium abundances in the Guidong granite body suggested that the insitu melting resulted in enrichment of uranium and thorium elements at the top of the crustal granite layer, and caused spatial separation of the two elements which is shown by the fact that the maximal abundance zone of uranium in a granite body is generally located over that of thorium. Multiple insitu melting led not only to the formation of a composite granite body (CGB), but also to the enrichment of uranium in the younger members of the CGB. Characteristics of relatively higher uranium and lower thorium contents in the eastern part of the Early Yanshanian granite of Guidong CGB are considered to be related to the original buried depth of the sourcelayer of uranium (the SinianPrecambrian strata) while the difference of uranium abundance from south to north of the CGB is related to the attitude and erosion of the MI of the latest stage. It is concluded that the coexistence of high uranium content and high U/Th ratio usually indicates the possibility of a concealed granite body, which is of practical significance for exploration of concealed uranium deposits. Related Articles | Metrics

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Tectonic characteristics of the Xiazhuang uranium orefield and its hydrothermal uranium mineralization. 2011, 18(1): 118-125.  Abstract ( 1982 )   PDF (2127KB) ( 1222 )   The Xiazhuang hydrothermal uranium orefield is located in the east part of IndosinianYanshan Guidong composite granite body, where developed three systems of NWW, NNE and NENEE faults. On the basis of the former research and our field and thin section investigations, the fault features, their active history and tectonic stress field since Indosinian tectonic movement are preliminarily revealed. Combining the explanation of insitu melting theory of granite, we have reached the following considerations: the NWW faults and NNE faults that were probably originated from conjugation shearing joints in the Late Jurassic had developed into two major fault systems in the orefield in the early Cretaceous. The former were extended so as to control the intrusion of diabase magma, and the latter were sheartensional so as to control coarse to microcrystallized quartz veins and various alterations. Nearly at the end of the early Cretaceous the NNE faults developed into ductile shear zones and then in the late Cretaceous changed to dextral tensional activities, which partly controlled intrusion of diabase magma. NENEE structures were mainly folds and reverse faults in the Jurassic and the NENEE faults changed to sinistral compressshear ones in the early Cretaceous and then changed to tensional ones in the late Cretaceous, which controlled the formation of the red bed basin. In transitional period from the early to late Cretaceous, regional compression stress changed from NWSE to NESW. The Guidong granite body experienced multimelting in IndosinianYanshan tectonic movement, provided very good conditions for reactivation, migration and enrichment of uranium. Two mineralization stages of uranium in the early and late Cretaceous are considered to be related to two remelting events of granite magma layers. When melting interface (MI) moved upwards and granite magma layer melted, faults cut shallowly into remelting layer and became “gateways” for magma hydrothermal fluid. However, when MI moved downwards and granite magma layer crystallized, faults could cut deeply down into the lower part of remelting layer and became “gateways” for basic magma. Because of more intensive tension, NWW faults were major “gateways” for basic magma. NENEE faults were relatively smaller ones, often acted as “host structure”. Whereas NNE faults as relatively larger ones were tensional in the early to late Cretaceous so as to become major “gateways” for uprising of uranium bearing fluid and became important “gateway structure”. When upward migration of the oreforming fluid met diabase dyke, the uranium was reduced so that was enriched. When entering into NENEE faults, the uranium bearing fluid was “jammed” and concentrated. The two locations were all favorable places for mineralization of hydrothermal uranium. Layer granite+“uranium mineralization horizon”+faults are thought to be guiding principles for finding deeper and hidden uranium mines in the Xiazhuang orefield. Related Articles | Metrics

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Mineralization relevant to repeated crustal melting: An example from the ZCGB, Gansu Province. 2011, 18(1): 126-132.  Abstract ( 1725 )   PDF (2091KB) ( 1223 )   On the basis of the insitu melting model of granite genesis, the authors reencoded the geological, geochemical and mineralogical data concerning the Zhongchuan composite granite body (ZCGB) and found that the ZCGB was formed by repeated crustal melting in the earlier Mesozoic. Repeated crustal melting resulted in not only the formation of a homocentric structure and the evolution of chemical composition of the ZCGB, but also the mineralization of different oreforming elements. Relatively high goldbearing rockstrata involved in the earlier Mesozoic melting process of this area led to the enrichment of gold in hydrothermal stage and the formation of numerous gold and polymetal sulfide deposits in the covering strata over the Indosinian and the Early Yansanian granite layers. According to the NNE fracture system developed within the ZCGB and the remnants of hydrothermal activity within the fractures, a remelting event was very likely to occur in the Late Cretaceous to the Early Cenozoic in the lower part of the Early Mesozoic granite layer.  Repeated melting would increase oxygen fugacity f(O2) of magma system, leading U4+ to change into U6+ that would be not able to enter the lattice of silicates and thus be expelled out of the magma system during the hydrothermal stage, forming the “granitetype” uranium veins within the fracture in the old covering granite layers. Related Articles | Metrics

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Mineralization mechanism of the Daguanchang UMo polymetallic deposit and its application in ore prospecting. 2011, 18(1): 133-140.  Abstract ( 4226 )   PDF (17412KB) ( 4804 )   The UMo polymetallic deposits located in the Guyuan volcanic basin in the northern rim of northern China terrain attract more and more attentions of geoscientists in China. The UMo polymetallic deposits were considered to have genetic relation to the orehosted volcanic rocks. On the basis of the insitumelting model of granite origin, together with geologic and geophysical features of the Daguanchang UMo polymetallic deposit, it is concluded that the Daguanchang UMo deposit was originated from the activities of porphyries in the deeper localities under the volcanic rocks. It is also proposed that the upheaval domain of the granitic remelting interface was located at the axial region of the anticline where is suggested to be the optimum locality for porphyry Mo ore prospecting. Related Articles | Metrics

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A discussion on the formation of granite in the Pearl River Mouth Basin and its implication to hydrocarbon resource. 2011, 18(1): 141-148.  Abstract ( 2131 )   PDF (1668KB) ( 5161 )   The analysis of the geochemical and geophysical characteristics of Yanshan Period granite in the Pearl River Mouth Basin suggested that the uplifting of the lithosphere isothermal surface and multiple melting of the upper crust, which resulted from the subduction of the Pacific plate under the South China plate, gave rise to the formation of the granite. The granite dome and drape anticline on the uplifting part of the basin was formed by the regional erosion and the sedimentation in the Cenozoic afterwards. The drape anticline was one of the most important tectonic types of oil and gas bearing structure in Pearl River Mouth Basin. The Dongsha Rise and its northern region are characterized by hightemperature geothermal field in the Mesozoic and the granite, while the southern depression is featured by lowertemperature geothermal field and the Mesozoic sedimentary. Owing to the low thermal evolution of source rock in the southern depression, there was a possibility that secondary hydrocarbon generation could occur in the Cenozoic. Related Articles | Metrics

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Geology, geochemistry and chronology of Lailisigaoer3571 porphyry CuMo orefield, western Tianshan, Xinjiang. 2011, 18(1): 149-165.  Abstract ( 2797 )   PDF (4376KB) ( 2503 )   It faces much difficulty to find the porphyry copper deposit in western Tianshan, Xinjiang, and it is essential to research on the CuMo mineralization. The 3571 Cu deposit was recently found next to the Lailisigaoer Mo deposit, and they constitute the Lailisigaoer3571 CuMo orefield. It is suggested that the CuMo orefield occurred in the Early Carboniferous continental margin arc which was formed by the Junggar oceanic crust subduction under the KazakhstanYili Plate. The Siluric siltmud hornstones were intruded by several small granodiorite porphyry bodies in the orefield, and CuMo mineralization may have happened during the structure movement, magma activity and hydrothermal processes on the continental margin arc setting. The CuMo sulfide orebody in shape of veins, tabular and lens occurred in the top or edge parts of the granodiorite porphyry, contact belts and the wallrock nearby. The hydrothermal alterations changed from Ksilication to sericitization, and then propylitization, and the mineralization shows the change in the structure of ores from dissemination to veindissemination, and then veins. The major ore minerals include molybdenite, chalcopyrite, pyrrhotine, bornite, and pyrite. The mineralization is characterized by a porphyry CuMo type. The granodiorite porphyry is rich in Si, Al, K, Na, Rb, Ba, Th, and poor in Mg, Ta, Hf, Zr, Sm, Sr, Y, and Yb, and the trace element character is similar to that of continental margin granites. The average ∑REE of the porphyry is 133.84×10-6 and lower than that of Stype granites. ISr is from 0.7079 to 0.7103, εNd(t) is from -0.61 to -3.71, and the magma was from the mantlecrust mixing or the lower crust. The ore δ34SVCDT is from 2.7‰ to 4.3‰, 206Pb/204Pb from 18.0997 to 18.2588, 207Pb/204Pb from 15.6052 to 156242, 208Pb/204Pb from 38.1245 to 38.3078, and the metal was from the upper mantle and lower crust directely related to the continental margin arc magma. The δ18OH2O VSMOW of the late stage oreforming fluid is from -1.33‰ to 5.46‰,  δDH2O VSMOW from -81‰ to -101‰, and the water in the oreforming fluid is mainly the magma water with meteoric water mixed. The porphyry was dated as 346±1.2 Ma in the Lailisigaoer Mo oredistrict and 350±0.65 Ma in the 3571 Cu oredistrict by LAICPMS UPb method. The CuMo mineralization occurred in the Early Carboniferous Period. The Lailisigaoer3571 CuMo orefield should have been in the same metallogenic series with the Axi Au orefield, and this is very important for the exploration in western Tianshan, Xinjiang. Related Articles | Metrics

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Constraints of dike thicknesses on the metallogenesis and its application to the Shihu gold deposit. 2011, 18(1): 166-178.  Abstract ( 2189 )   PDF (3075KB) ( 1502 )   According to the metallogenic theory of the transmagmatic fluids, the magma body is not the source of orebearing fluids, but the channel for the fluids. Thus, it will be an effective way to estimate the ore forming potential by calculating the content of fluids injected into the magma body. Onedimensional heat transfer model is used to calculate the cooling time with different thicknesses of three representative types of dikes (granite porphyry, quartz diorite and diabase) in Shihu gold mine. The change rate of magma viscosity during the cooling is also estimated. Assuming that these magmas have been emplaced at ～6 km depth and that the orebearing fluid could not be effectively injected into the magma body only after these magmas were fully crystallized, we obtained the minimum critical thickness of mineralization of three representative types of dikes as follows: 3345 m for granite porphyry, 822 m for quartz diorite and 102 m for diabase in Shihu gold mine. Simulation results are consistent with the occurrence of ore bodies, suggesting that they are of practical value. According to the length/width ratio of the dike, the minimal critical oreforming intrusion outcrop area is estimated: 3121561 m2 for diabase, 00140068 km2 for quartz diorite and 00110034 km2 for granite porphyry. This kind of estimation provides a qualitative standard for field geological prospecting, and has certain reference value for rapid exploration. Related Articles | Metrics

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C, O, S and Pb isotopes characteristics and sources of the ore metals of the Lengshuikeng AgPbZn ore field, Jiangxi. 2011, 18(1): 179-193.  Abstract ( 5121 )   PDF (2810KB) ( 10430 )   The Lengshuikeng ore field in Jiangxi Province is one of the most important AgPbZn deposits in northern Wuyi Mountains, China. It is a rare typical porphyry AgPbZn deposit in the world and a volcanic sedimentaryhydrothermal reworked deposit with unique features, so it is worthy of detailed research. The δ34S values of chalcopyrite, pyrite, sphalerite, and galena sulfides collected from the Lengshuikeng ore field range from -380‰ to +694‰ with an average of +187‰. The narrow distribution of δ13C values around -411‰ and the δ34S values with ~+2‰ peak value suggest that the sulfur and carbon of the oreforming fluid were derived from hypomagma, but it did not exclude the possibility that a certain amount of sulfur and carbon were provided by the hosted strata. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulfide ores range respectively within 1777117867, 1556415685 and 3823538652. But, the volcanic rock, volcanicsedimentary rock, and metamorphic rock contain higher radiogenic lead with the 206Pb/204Pb ratios of 1789918220, showing both relevance and disparity between rock lead and ore lead. However, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of the ore and granite porphyry leads are similar and lie on the same lines in the diagrams of 208Pb/204Pb vs. 207Pb/204Pb and 207Pb/204Pb vs. 207Pb/204Pb. For the mixing lines, the two end members are respectively upper crust and mantle, which means mixing the matters of the upper crust and of the mantle. All the evidences strongly support that the metallogenic elements were carried by the porphyry magmatic system and strata. Therefore, the Lengshuikeng ore field is a typical magmatichydrothermal type of ore deposit associated with subvolcanic rocks, and formed on the intracontinental setting in Eastern China during the midYanshanian period. Related Articles | Metrics

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Actual traces of mantle fluid of Jinding superlarge PbZn deposit and the mechanism of crustmantle overlapping 2011, 18(1): 194-206.  Abstract ( 2682 )   PDF (4010KB) ( 1403 )    On the basis of  the studies of sandstonetype and brecciolatype ores from Jinding superlarge leadzinc deposit in western Yunnan Province by systematically using petrography, electron microprobe, scanning electron microscopy and energy spectroscopy, and combined with the studies of isotopic geochemistry, we confirmed that the black opaque cements are the microproducts of speedily cooling of carbonatite melt which mixed heterogeneously with sulfides, and that they are the relic actual traces of mantle fluid contaminated with crustal fluid. The crustmantle transitive characteristics of noble gases in fluid inclusions from ore minerals suggested that during the transportation and mineralization processes of mantle fluid, the crustal fluid had made great contribution. The distribution style of Pb isotope provides a new understanding of the behaviors of Pb isotope in the crustmantle overprinted processes. We propose the main geochemical mechanism of the Jinding leadzinc deposit as follows: the mantle fluid derived from alkalirich porphyry transported along deep faults, metasomatically altered host rocks and was overprinted by crustal fluids. Related Articles | Metrics

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Geochronological study of magmatic intrusions and mineralization of Machangqing porphyry CuMoAu deposit,Western Yunnan Province 2011, 18(1): 207-215.  Abstract ( 1784 )   PDF (1731KB) ( 1218 )    The Machangqing porphyry CuMoAu deposit is one of the typical deposits associated with the alkalinerich porphyry in the JinshajiangAilaoshan tectonic belt of the Himalayan epoch. Alkalite intrusive rock is a superimposed intrusive complex formed by multiperiodic and multistage magmatic activities. The time limit of magmatic activity is 6429 Ma. In situ zircon LAICPMS UPb ages and molybdenite ReOs ages indicate that the age of orebearing granite prophyry is 3793±082 Ma, whereas the mineralization age is 3472±05 Ma, which shows that the mineralization mainly related to the later magmatic activity. The closeness among zircon UPb, molybdenite ReOs, and KAr ages in the Machangqing porphyry indicates that the oreforming system cooled from about 800 ℃(zircon crystallization temperature) through 500 ℃(closure temperature for ReOs in molybdenite) to below 300 ℃(closure temperature for Ar in biotite) in a very short period. The duration of the Machangqing giant oreforming system is less than 2 Ma. The porphyry copper and molybdenum deposit of JinshajiangAilaoshan mineralization belt was the product of the synmineralization, and the mineralization time limit focused on 4035 Ma. Related Articles | Metrics

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Modal analysis of montmorillonite in bentonites using phase mixing equation: A comparative study. 2011, 18(1): 216-221.  Abstract ( 1660 )   PDF (854KB) ( 1117 )    According to the mass balance principle, the mineral contents of the bentonites from Yangxian of Shaanxi Province, Queshan of Henan Province, and Chifeng of the Inner Mongolia Autonomous Region were estimated by solving the phase mixing equation constructed from the data of Xray diffraction, microprobe analysis of montmorillonite grains, and wet chemical analysis of the bentonites. The crystal formulas of montmorillonite in the bentonites were calculated by using the anion hydrogen equivalent method. The cell lattice constants of the principal minerals in the bentonites were calculated with a FORTRAN90 program CELLSR. Compared with both methods of the methylene blue absorption and XRD Rietveld multiphase analysis, the phase mixing equation was confirmed to be the most accurate modal analysis method for determining the content of montmorillonite in bentonites with several minerals coexisted. Related Articles | Metrics

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Female cones of Elatides from the Lower Cretaceous Bantou Formation of Yongan, Fujian Province. 2011, 18(1): 222-230.  Abstract ( 1774 )   PDF (3729KB) ( 823 )   Some female cones of Elatides were collected from the Lower Cretaceous Bantou Formation, Yongan City, Fujian Province. The present authors have studied the gross morphology and cuticular features of them. These cones are all detached from the vegetative shoots, quite small and compact, with many cone scales. They are helically arranged along the cone axis, and their apices are spiny. The characteristics described above are consistent with the genus Elatides. According to the morphological characters of the cones, and the features of the cone scales and axis, these cones are recognized as three species: one new species Elatides yonganensis Dai et Sun, sp. nov., one published species Elatides cf. curvifolius and one indeterminate species Elatides sp. The morphology of new species E. yonganensis has been especially described and compared in detail with other Chinese and European species. Elatides Yonganensis is different from the previously published species by its characters of flexuous cone axis, much longer and spiky apex of bracts, membranous ligules with serrate distal margin and probably five seeds on every adaxial cone scales. Additionally, the fossil records of Elatides in China have been reviewed and discussed. The occurrence of the Elatides cones in the Bantou Formation of Yongan City, Fujian Province, has extended the distribution range of Elatides to 25°N, and added the fossil records. Related Articles | Metrics

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Clarification of the physical definition of a field. 2011, 18(1): 231-235.  Abstract ( 1643 )   PDF (3768KB) ( 1047 )    This paper clarifies a misleading in the definition of physical field made by authoritative English dictionaries. The Longman Modern English Dictionary,  the Longman Dictionary of Contemporary English, the Oxford Advanced Learners Dictionary, the MerriamWebsters Advanced Learners English Dictionary,  the Encyclopedic Dictionary of Applied Geophysics as SEGs standard for terms particular to geophysical technology,  Chinese geophysical textbooks, monographs, and dictionaries  have defined physical field as an area, a space or a region. The definitions differ significantly from another definition in the theory of fields and another geophysical literature, which is usually given as an effect or a force. Defining the physical field as an area, a space or a region confuses the field itself with the space throughout which the field exists, and is not a standard physics definition of a field. A new definition of the physical field based on the theory of fields is proposed as follows: a physical effect existing in a space. Related Articles | Metrics