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1
2013, 46(3): 1-38.
Abstract：
Supercontinents are assemblies of all or nearly all (> 90%) of the earth's continental blocks. The oldest supercontinent speculated is the one at 3.0 Ga termed as Ur. It is difficult to test the existence of this supercontinent due to its old age. There appear to have been twice in earth history when all of the continents were fused into one supercontinent. The first truly coherent supercontinent in earth history was probably Columbia, which formed between 1.85 and 1.90 Ga, began to fragment at ~1.6 Ga, and finally broke up at ~1.3-1.2 Ga. Columbia was followed by the second supercontinent Rodinia, which lasted from ~1100 Ma to 540 Ma. The Pangea (0.25 Ga) was not a true supercontinent, but an unusually large assembly of continents making a semi-supercontinent. The southern half (Gondwanaland) of this semi-supercontinent has a dispersion history, and the northern half (Laurasia, i.e. Paleo-Asia) has an amalgamation history. At present, the third supercontinent has not formed yet, and our planet is in midway to make a true supercontinent (Amasia) in the future. The mechanisms of formation and disruption of supercontinents have been two controversial topics. A synthesis of some of the recent conceptual models suggests that mantle dynamics exerted a significant control on the assembly and breakup of supercontinents through the history of the Earth. The formation process of supercontinents is controlled by super downwelling that develops through double-sided subduction zones as seen in present-day western Pacific, and also endorsed by both geologic history and P-wave whole mantle tomography. The super downwelling swallows all material like a black hole in the outer space, pulling together continents into a tight assembly. The fate of supercontinents is managed by superplumes (super-upwelling) which break apart the continental assemblies. With the advancement in numerical modeling techniques as well as the enhancement in computational power and resource, the numerical studies of mantle dynamics have markedly progressed toward the realization of seismic tomography images of mantle structure and a better understanding of geodynamic mechanisms. The solid Earth can be considered to comprise a plate tectonics domain with broadly horizontal motion in the upper mantle, plume tectonics dominated by vertical movements in the lower mantle region and an "anti-plate tectonics" zone characterized by horizontal movements at the bottom of the mantle. Although mantle tomography opens windows into the deep Earth, the imbricated remnants of "ocean plate stratigraphy" preserved in accretionary orogens still constitute useful geological tools to study subduction-accretion-collision history, particularly in relation to the assembly of older supercontinents on the surface of the globe. The dynamics of supercontinents also impact the origin and extinction of life, surface environmental changes as well as magmatism and metallogeny. Massive flow of material and energy was induced by mantle downwelling and upwelling accompanied by supercontinent assembly and breakup, which would also lead to large-scale magmatism and metallogeny, catastrophic environmental changes, sometimes even triggering mass extinction. When a rising mantle plume impinges the base of a supercontinent, the consequent continental rifting, formation of large igneous provinces, large scale metallogeny and volcanic emissions might lead to the initiation of a plume winter, the aftermath of which would be mass extinction and long-term oceanic anoxia. Supercontinent tectonics in relation to mantle dynamics thus provides a key to evaluate the history of evolution and destruction of the continental crust, to carry out the resource assessment, to understand the history of life, and to trace the major surface environmental changes of our planet.
Supercontinents are assemblies of all or nearly all (> 90%) of the earth's continental blocks. The oldest supercontinent speculated is the one at 3.0 Ga termed as Ur. It is difficult to test the existence of this supercontinent due to its old age. There appear to have been twice in earth history when all of the continents were fused into one supercontinent. The first truly coherent supercontinent in earth history was probably Columbia, which formed between 1.85 and 1.90 Ga, began to fragment at ~1.6 Ga, and finally broke up at ~1.3-1.2 Ga. Columbia was followed by the second supercontinent Rodinia, which lasted from ~1100 Ma to 540 Ma. The Pangea (0.25 Ga) was not a true supercontinent, but an unusually large assembly of continents making a semi-supercontinent. The southern half (Gondwanaland) of this semi-supercontinent has a dispersion history, and the northern half (Laurasia, i.e. Paleo-Asia) has an amalgamation history. At present, the third supercontinent has not formed yet, and our planet is in midway to make a true supercontinent (Amasia) in the future. The mechanisms of formation and disruption of supercontinents have been two controversial topics. A synthesis of some of the recent conceptual models suggests that mantle dynamics exerted a significant control on the assembly and breakup of supercontinents through the history of the Earth. The formation process of supercontinents is controlled by super downwelling that develops through double-sided subduction zones as seen in present-day western Pacific, and also endorsed by both geologic history and P-wave whole mantle tomography. The super downwelling swallows all material like a black hole in the outer space, pulling together continents into a tight assembly. The fate of supercontinents is managed by superplumes (super-upwelling) which break apart the continental assemblies. With the advancement in numerical modeling techniques as well as the enhancement in computational power and resource, the numerical studies of mantle dynamics have markedly progressed toward the realization of seismic tomography images of mantle structure and a better understanding of geodynamic mechanisms. The solid Earth can be considered to comprise a plate tectonics domain with broadly horizontal motion in the upper mantle, plume tectonics dominated by vertical movements in the lower mantle region and an "anti-plate tectonics" zone characterized by horizontal movements at the bottom of the mantle. Although mantle tomography opens windows into the deep Earth, the imbricated remnants of "ocean plate stratigraphy" preserved in accretionary orogens still constitute useful geological tools to study subduction-accretion-collision history, particularly in relation to the assembly of older supercontinents on the surface of the globe. The dynamics of supercontinents also impact the origin and extinction of life, surface environmental changes as well as magmatism and metallogeny. Massive flow of material and energy was induced by mantle downwelling and upwelling accompanied by supercontinent assembly and breakup, which would also lead to large-scale magmatism and metallogeny, catastrophic environmental changes, sometimes even triggering mass extinction. When a rising mantle plume impinges the base of a supercontinent, the consequent continental rifting, formation of large igneous provinces, large scale metallogeny and volcanic emissions might lead to the initiation of a plume winter, the aftermath of which would be mass extinction and long-term oceanic anoxia. Supercontinent tectonics in relation to mantle dynamics thus provides a key to evaluate the history of evolution and destruction of the continental crust, to carry out the resource assessment, to understand the history of life, and to trace the major surface environmental changes of our planet.
2
Abstract：
The Tian shan Carboniferous-Early Permian riftrelated volcanism in northw estern China represents anewly-recognized largeigneous province extending over at least 1.7×106km2.The volcanic successions comprise thick piles of basaltic lavas and subord inate intermediate and silicic lavas and pyroclastics,and are in terpreted to result fromamantle plume with component of εNd(t)≈+5,(87Sr/86Sr(t)≈0.704 and La Nb≈0.9.On the basis of petrogeochemical data,the Carboniferous-Early Permian basic lavas can be classified in to high-Ti/Y(HT,Ti/Y>500)and low-Ti/Y(LT,Ti/Y<500)magma types.The LT lavas can be further divided in to four sub types:LT1,LT2,LT3 and LT4.The chemical evolution of the LT1,LT2(in central Tian shan and Baishan of Gansu),LT4(in western Tian shan, Jungar and Baishan of Xinjiang)and LT3,HT(Tarim)lavas is controlled by an olivine(ol)+clinopy roxene(cpx)fractionation,but gabbroic fractionation accounts for the chemical variation of the LT4 lavas from eastern Tianshan.Elemental and isotopic data suggest that the chemical variation of the Carboniferous-Early Permian riftrelated basic lavas in the Tianshan and their neighboring areas can not be explained by crystallization from a commonparental magma.The Sr-Nd isotopic variation of the crustally contaminated LT3 and LT4 lavas is related to the nature of lithosp here through which the plume-derived melts have erupted.
The Tian shan Carboniferous-Early Permian riftrelated volcanism in northw estern China represents anewly-recognized largeigneous province extending over at least 1.7×106km2.The volcanic successions comprise thick piles of basaltic lavas and subord inate intermediate and silicic lavas and pyroclastics,and are in terpreted to result fromamantle plume with component of εNd(t)≈+5,(87Sr/86Sr(t)≈0.704 and La Nb≈0.9.On the basis of petrogeochemical data,the Carboniferous-Early Permian basic lavas can be classified in to high-Ti/Y(HT,Ti/Y>500)and low-Ti/Y(LT,Ti/Y<500)magma types.The LT lavas can be further divided in to four sub types:LT1,LT2,LT3 and LT4.The chemical evolution of the LT1,LT2(in central Tian shan and Baishan of Gansu),LT4(in western Tian shan, Jungar and Baishan of Xinjiang)and LT3,HT(Tarim)lavas is controlled by an olivine(ol)+clinopy roxene(cpx)fractionation,but gabbroic fractionation accounts for the chemical variation of the LT4 lavas from eastern Tianshan.Elemental and isotopic data suggest that the chemical variation of the Carboniferous-Early Permian riftrelated basic lavas in the Tianshan and their neighboring areas can not be explained by crystallization from a commonparental magma.The Sr-Nd isotopic variation of the crustally contaminated LT3 and LT4 lavas is related to the nature of lithosp here through which the plume-derived melts have erupted.
3
Abstract：
The Nagengkangqieer silver polymetallic deposit, with proved silver quantity of over 2 000 tons, is a large-scale deposit recently discovered in the eastern part of the East Kunlun area, which has become the first large independent silver deposit discovered in Qinghai Province and also has a potential of being supergiant one in size. Based on the study of the geological background, deposit characteristics, ore structure and country rock alteration of the mining area, the ore controlling elements and prospecting direction of this deposit have been analyzed in this paper, and the origin of this deposithas been discussed, which is considered to be related to the volcanic activity of Triassic continental facies. The ore body is located in the volcanic formation, mainly consisting of rhyolite, andesite and dacite, which has been controlled by the NW fault and belongs to the continental volcanic-subvolcanic type of the epithermal deposit(also known as the volcanic hydrothermal type).
The Nagengkangqieer silver polymetallic deposit, with proved silver quantity of over 2 000 tons, is a large-scale deposit recently discovered in the eastern part of the East Kunlun area, which has become the first large independent silver deposit discovered in Qinghai Province and also has a potential of being supergiant one in size. Based on the study of the geological background, deposit characteristics, ore structure and country rock alteration of the mining area, the ore controlling elements and prospecting direction of this deposit have been analyzed in this paper, and the origin of this deposithas been discussed, which is considered to be related to the volcanic activity of Triassic continental facies. The ore body is located in the volcanic formation, mainly consisting of rhyolite, andesite and dacite, which has been controlled by the NW fault and belongs to the continental volcanic-subvolcanic type of the epithermal deposit(also known as the volcanic hydrothermal type).
4
Abstract：
Kuzigan alkaline complex is one of the major parts of the Taxkorgan alkaline complexterrane. It is mainly composed of aegirine-augite syenite, quartz aegirine-augite syenite, and alkali granite. There is great difference among the three rocks in the content of SiO2, 50.26%-54.11%, 59.74%-60.43% and 69.59%-72.13% for aegirine-augite syenite, quartz aegirine-augite syenite and alkali granite, respectively. Aegirine-augite syenite and quartz aegirine-augite syenite has similar Rittman index, namely 7.83-10.97 and 8.51-9.05, distinctly differing from 2.49-3.71 of alkali granite. These three rocks are strongly enriched in light rare earth elements (LREE) as well as some large ion lithophile element (LILE), such as Rb, Ba, Sr, and depleted in High Field Strength Element (HFSE) such as Nb, Ta and Ti. Abnormal high Sr, Ba and ∑ REE content may imply the mixing of enriched mantle materials. LA-ICP-MS in-situ zircon U-Pb dating obtain the ages of 10.9±0.1 Ma and 11.9±0.4Ma for the quartz aegirine-augite syenite and alkali granite respectively, representing the crystallization ages of the two rocks. The εHf(t) values of the quartz aegirine-augite syenite and alkali granite are of -9.78-3.24 and -13.54-5.78, showing the crust-mantle mixing in magma source area. According to the comprehensive analysis and combined with regional geological data, we preliminarily hypothesized that the Kuzigan alkaline complex is a product of the crust-mantle mixing, which is caused by the asthenosphere flowing northward due to the delamination of the Tibetan plateau at ~25Ma, and the asthenosphere upwelling as a result of the obstruction of the root of the Tarim craton lithosphere. Therefore, the formation of the complex is a fernwirkung of the magmation after Tibetan plateau large-scale delamination, and it signifies that during ~11 Ma the study area was in extensional tectonic setting.
Kuzigan alkaline complex is one of the major parts of the Taxkorgan alkaline complexterrane. It is mainly composed of aegirine-augite syenite, quartz aegirine-augite syenite, and alkali granite. There is great difference among the three rocks in the content of SiO2, 50.26%-54.11%, 59.74%-60.43% and 69.59%-72.13% for aegirine-augite syenite, quartz aegirine-augite syenite and alkali granite, respectively. Aegirine-augite syenite and quartz aegirine-augite syenite has similar Rittman index, namely 7.83-10.97 and 8.51-9.05, distinctly differing from 2.49-3.71 of alkali granite. These three rocks are strongly enriched in light rare earth elements (LREE) as well as some large ion lithophile element (LILE), such as Rb, Ba, Sr, and depleted in High Field Strength Element (HFSE) such as Nb, Ta and Ti. Abnormal high Sr, Ba and ∑ REE content may imply the mixing of enriched mantle materials. LA-ICP-MS in-situ zircon U-Pb dating obtain the ages of 10.9±0.1 Ma and 11.9±0.4Ma for the quartz aegirine-augite syenite and alkali granite respectively, representing the crystallization ages of the two rocks. The εHf(t) values of the quartz aegirine-augite syenite and alkali granite are of -9.78-3.24 and -13.54-5.78, showing the crust-mantle mixing in magma source area. According to the comprehensive analysis and combined with regional geological data, we preliminarily hypothesized that the Kuzigan alkaline complex is a product of the crust-mantle mixing, which is caused by the asthenosphere flowing northward due to the delamination of the Tibetan plateau at ~25Ma, and the asthenosphere upwelling as a result of the obstruction of the root of the Tarim craton lithosphere. Therefore, the formation of the complex is a fernwirkung of the magmation after Tibetan plateau large-scale delamination, and it signifies that during ~11 Ma the study area was in extensional tectonic setting.
5
2013, 46(3): 212-221.
Abstract：
Due to the fact that gold deposits in the Xiqingshan area is significantly controlled by tectonic structures, studying the structure of this area is the key of metallogenic prediction. In this paper, based on field geological investigation and remote sensing interpretation method, we studied the remote sensing geology and the gold distribution regulation of the Xiqingshan area. The results showed that: in the Xiqingshan area, a NWW gold deposit belt was formed, west from the Nanmurang, by Zhongqu and Dashui gold deposits, east to the Junmuchang. There are four gold ore fields equidistantly in this gold deposit belt. From west to east, they are Nanmurang gold ore field, Zhongqu gold ore field and Dashui gold ore field. Each of them has a number of gold deposits and gold ore occurrence. The Junmachang area in the east is the centralized area of remote sensing mineralization information, and may become a potential gold ore field. In each ore field, the favorable position of gold deposit is the centralized interchange of the NWW faults with the NW, NNE and NE fault, and near the edge of the ring structure. On this basis, we predicted 7 favorable metallogenic zones.
Due to the fact that gold deposits in the Xiqingshan area is significantly controlled by tectonic structures, studying the structure of this area is the key of metallogenic prediction. In this paper, based on field geological investigation and remote sensing interpretation method, we studied the remote sensing geology and the gold distribution regulation of the Xiqingshan area. The results showed that: in the Xiqingshan area, a NWW gold deposit belt was formed, west from the Nanmurang, by Zhongqu and Dashui gold deposits, east to the Junmuchang. There are four gold ore fields equidistantly in this gold deposit belt. From west to east, they are Nanmurang gold ore field, Zhongqu gold ore field and Dashui gold ore field. Each of them has a number of gold deposits and gold ore occurrence. The Junmachang area in the east is the centralized area of remote sensing mineralization information, and may become a potential gold ore field. In each ore field, the favorable position of gold deposit is the centralized interchange of the NWW faults with the NW, NNE and NE fault, and near the edge of the ring structure. On this basis, we predicted 7 favorable metallogenic zones.
6
Abstract：
By studying the geological features of Lüliangshan copper deposit and Shuangkoushan lead-zinc deposit in the northern margin of Qaidam Basin Mountains,the author indicate that the adjacent rock of that two deposit is Ophiolite tectonic blocks that subjected to intense tectonic deformation fold and lower green-schist facies metamorphism,ore body which shows veined or like-layered occurs in the strong ductile shear zone band,respectively link to the two collision orogenesis,Caledonian and late Variscan to Indo-Chinese epoch,and probably corresponds with the formation of orogenic gold deposits of this area simultaneously.A series of Au dispersed flow element anomalies which has been found in the periphery district of Lüiangshan Copper and the Shuangkoushan lead-zinc are the cludes to looking for important target areas of potential orogenic-type gold deposits,and the indicating location of previously discovered VHMS copper mineralization in the Lüliangshan and SEDEX lead-zinc mineralization in the Shuangkoushan is important target area to look for post-transformation Qinglongtan-type copper mineralization and Xitieshan-type lead-zinc mineralization.
By studying the geological features of Lüliangshan copper deposit and Shuangkoushan lead-zinc deposit in the northern margin of Qaidam Basin Mountains,the author indicate that the adjacent rock of that two deposit is Ophiolite tectonic blocks that subjected to intense tectonic deformation fold and lower green-schist facies metamorphism,ore body which shows veined or like-layered occurs in the strong ductile shear zone band,respectively link to the two collision orogenesis,Caledonian and late Variscan to Indo-Chinese epoch,and probably corresponds with the formation of orogenic gold deposits of this area simultaneously.A series of Au dispersed flow element anomalies which has been found in the periphery district of Lüiangshan Copper and the Shuangkoushan lead-zinc are the cludes to looking for important target areas of potential orogenic-type gold deposits,and the indicating location of previously discovered VHMS copper mineralization in the Lüliangshan and SEDEX lead-zinc mineralization in the Shuangkoushan is important target area to look for post-transformation Qinglongtan-type copper mineralization and Xitieshan-type lead-zinc mineralization.
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