Giant Mineral Deposits and Their Geodynamic Setting in the Lanping Basin, Yunnan, China

There are giant mineral deposits, including the Jinding Zn-Pb and Baiyangping Ag-Co-Cu, and otherimportant mineral deposits (e.g., Baiyangchang Ag-Cu, Jinman Cu deposits, etc.) in the Lanping Mesozoic-Cenozoic Basin, Yunnan Province, China. The tabular ore-bodies and some veins hosted in terrestrial clastic rocks of the Mesozoic-Cenozoic age and no outcropping of igneous rocks in the giant deposits lead to the proposal of syngenetic origin, but the giant mineral deposits are not stratabound (e.g. MVT, sandstone- and Sedex-type). They formed in a continental red basin with intense crust movement. The mineralization is controlled by structures and lithology and occurs in different strata, and no sedimentary nature and no exhalative sediments are identified in the deposits. The deposits show some relations with organic matter (now asphalt and petroleum) and evaporates (gypsum). The middle-low-temperature (mainly 110℃ to 280℃) mineralization took place at a depth of about 0.9 km to 3.1 km during the early Himalayan (58 to 67 Ma). The salinity of ore-forming fluids is surprisingly low (1.6% to 18.0 wt% (NaCl)eq). Affected by the collision of the Indian and Eurasian plates, the mantle is disturbed under the Lanping Basin. The large-scale mineralization is closely linked with the geodynamics of the crust movement, the mantle and mantle-flux upwelling and igneous activity. Giant mineral deposits and their geodynamic setting are unique in the Lanping Basin.

Metallogenesis related to Mesozoic Granitoids in the Nanling Range, South China and Their Geodynamic Settings

Affected by the compressive stress from the South-Central （Indo-China） Peninsula, the Indosinian orogenesis, characterized by collision, thrust and uplifting, took place inside the South China Plate during 250-230 Ma. The ages of the Indosinian granitoids in the Nanling Range and vicinity areas are mostly 240-205 Ma, indicating that they were emplaced in both late collision and post-collision geodynamic environments. No important granite-related metallogenesis occurred in this duration. A post-orogenic setting started at the beginning of the Yanshanian Period, which controlled large-scale granitic magmatism and related metallogenesis. This paper makes the first attempt to divide the Yanshanian Period into three sub-periods, i.e. the early, middle and late Yanshanian Periods, based mainly on the features of magmatism, especially granitoids and related metallogenesis and their geodynamic environments. The magmatic association of the Early Yanshanian （about 185-170 Ma） comprises four categories of magmatism, i.e. basalt, bimodal volcanics, A-type granite and intraplate high-K calc-alkaline （HKCA） magmatism, which indicates an extension-thinning of lithosphere and upwelling of mantle material to a relative small and local extent. Pb-Zn, Cu and Au mineralizations associated with HKCA magmatism represents the first high tide of Mesozoic metallogenesis in the Nanling Range area. During the middle Yanshanian, the lithosphere was subjected to more extensive and intensive extending and thinning, and hence mantle upwelling and basaltic magma underplating caused a great amount of crust remelting granitoids. This period can be further divided into two stages. The first stage （170-150 Ma） is represented by large-scale emplacement of crust remelting granites with local tungsten mineralization at its end. The second stage （150-140 Ma） is the most important time of large-scale mineralizations of non-ferrous and rare metals, e.g. W, Sn, Nb-Ta, Bi, Mo, Be, in the Nanling Range area. The late Yanshanian （140-65 Ma） was generally characterized by full extension and breakup of the lithosphere of South China. However, owing to the influence of the Pacific Plate movement, the eastern part of South China was predominated by subduction-related compression, which resulted in magmatism of calc-alkaline and shoshonite series and related metallogeneses of Au, Ag, Pb-Zn, Cu and （Mo, Sn）, followed by extension in its late stage. In the Nanling Range area, the late Yanshanian magmatism was represented by granitic volcanic-intrusive complexes and mafic dikes, which are genetically related to volcanic-type uranium and porphyry tin deposits, and the mobilization-mineralization of uranium from pre-existing Indosinian granites.

Geology and Geochemistry of the Shizitou Molybdenum Deposit, Jiangxi Province： Implications for Geodynamic Setting and Metallogenesis

The Shizitou molybdenum （Mo） deposit in Yongping, Jiangxi, is an important, recently discovered deposit in the eastern section of the Qin-Hang metallogenic belt. The Mo deposit is located in the outer contact zone behveen the porphyritic biotite granite and the Neoproterozoic migmatite, and present in the deep central part of the intrusion. Re-Os dating and S and Pb isotopic analysis have been conducted to assess the metallogenesis of the Shizitou Mo deposit. S, Pb and Re isotopes show that the ore-forming materials were derived from the porphyritic biotite granitic magma, which originated from the mixing of mantle and crust. Re-Os dating of molybdenite from the ores gives a model age from 156.9±2.2 to 158.5±2.4 Ma, with a weighted mean age of 158±1 Ma and an isochron age of 158.0±2.5 Ma. Geological and geochemical characteristics of the ore deposit and the related granitoids indicate that the Shizitou deposit is a Climax-type Mo deposit. Based on previous studies of the Qin-Hang metaliogenic belt, two metallogenic events are believed to have occurred during 172-145 Ma and 137-132 Ma. These two metallogenic periods are consistent with the timing of two metallogenic peaks during the middle to late Jurassic and the Cretaceous in South China. These events represent responses to the partial backarc extension associated with the subduction of the Izanagi plate beneath the Eurasian continent and the rapid northeastward movement of the subducting Izanagi plate.

The geology and geochemistry of the Shizitou molybdenum deposit, Jiangxi province, China: Implications for the geodynamic setting

1 Introduction The Qin-Hang suture zone is the most important polymetallic metallogenic zone in southern China[1-2]and has the greatest resource potential.In recent years,a group of molybdenum(Mo)deposits have been discovered in the northeastern part of the Qin-Hang belt[3].From Mar.2006to Dec.2014,the Jiangxi Copper Group Geological Exploration Engineering Co.,Ltd.conducted prospecting,

Tectonic and Geodynamic Setting of Oil and Gas Basins in China

About 26 sedimentary basins bearing oil and gas are developed in China. They can be classified into two main types . extensional basins and foreland basins . The former are chiefly distributed in the eastern part and the latter in the central and northwestern parts of the country . The present paper discusses the structural characteristics of these basins . including subsidence history , thermal history and structural style and kinematics . Combined with tectonic setting analysis of geophysical data and eruptive rocks , the geodynamic setting of the basins is established , and the formation mechanism of the basins is deduced to have been related to the subduction of the Izanagi and west Pacific plates and the closing of the Tethys ocean .

Metallogenesis and Geodynamic Setting of the Early Paleozoic Orogenic Gold Deposits in the North Altyn

The North Altyn has underwent a complex tectonic history in the Early Paleozoic and formed a number of orogenic gold deposits controlled by ductile to brittle shear zones adjacent to the southern side of the Northern Altyn Tagh fault e.g. the Dapinggou, Beiketan and Xiangyun. The Dapinggou gold deposit, a typical orogenic gold deposit in North Altyn, is predominantly hosted in the Precambrian carbonate and Cambrian volcano- sedimentary rocks which were strongly deformed and were subjected to low-grade metamorphism. The ore bodies occurred in K-feldspar quartz veins and hydrothermally altered mylonite within the ductile shear belt. Hydrothermal alteration including silicification, pyritization.

Geochronology of the Gabbro-mafic Microgranular Enclaves-granite Associations in the Gejiu District, Yunnan Province and Their Geodynamic Significance

Many igneous rocks distribute in Gejiu tin polymetallic ore-field at Yunnan province, rocks including basalt, gabbro, mafic microgranular enclaves, granites （porphyritic granite and equigranular granite） and akaline rocks. The ages of the granites and akaline rocks which are considered to have genetic connecting with the mineralization have been comfirmed, but the gabbro- mafic microgranular enclaves-granite assemblage＇s ages are still unknown. By means of LA-ICP-MS zircon U-Pb dating, the data of Shenxianshui equigranular granite, the mafic microgranular enclave in Jiasha area, the host rock of the mafic microgranular enclaves and the Jiasha gabbro are around ~80 Ma. Besides the above mentioned data, a group of new ages at ~30 Ma were discovered in this study, which is from gabbro and mafic microgranular enclaves. Based on the previous data and the new data gained this time, we suggest the major geochronology framework of the magmatism and mineralization events in Gejiu area is ~80 Ma, which is consistent with the Late Cretaceous magmatism and mineralization events in the whole southeast Yunnan and west Guangxi area and they were suggested to belong to the same geotectonic setting in late Yenshannian. And the new ages of the ~30 Ma obtained in this study is considered to represent a responding to the complicate tectonic evolution history of the Tibetan orogenic events in Cenozoic.

Geochronology and Geochemistry of the Early Paleozoic Ore-host Volcanic Sequence in the Kalatag Area,East Tianshan,NW China:Implications for the Tectonic Evolution

The East Tianshan contains many late Paleozoic magmatic and polymetallic deposits.Recent studies demonstrate that the early Paleozoic volcanic rocks discovered in the northern region of East Tianshan can be subdivided into the Daliugou,Hongliuxia and Kalatag formations.Here,we report zircon U-Pb ages of volcanic rocks and quartz diorite porphyry,together with whole-rock geochemical and Sr-Nd isotope data of early Paleozoic volcanic rocks,in order to investigate their petrogenesis and geodynamic setting.Zircon U-Pb analyses of the rocks suggest that the Kalatag Formation formed at ca.438-413 Ma.Geochemical characteristics of the early Paleozoic volcanic rocks exhibit typical subduction-related features.They have high Mg^(#)(44-75),positiveε_(Nd)(t)values(0.25-7.88),low^(87)Sr/^(86)Sr ratios(0.70457 to 0.70588)and young two-stage Hf isotope model ages(551-446 Ma),consistent with a depleted mantle origin with limited crustal contamination.The basaltic andesite and andesite have relatively high MgO contents(6.1-9.4 wt%),suggesting that they belong to high-magnesian andesites.They were most likely derived from the partial melting of mantle peridotite caused by the addition of fluids released by subducted oceanic slab.Based on regional geology,geochemical characteristics and previous studies,we infer that the southward subduction of the Junggar Ocean slab resulted in the generation of early Paleozoic volcanic rocks and arc setting-related metallogenic systems in the Kalatag area.

Laser Ablation ICP-MS U-Pb Zircon Geochronology of Granitoids and Quartz Veins in the Shihu Gold Mine, Taihang Orogen, North China: Timing of Gold-mineralization and Tectonic Implications

The Shihu gold deposit, situated in the Taihang Mesozoic orogen of the North China Craton （NCC）, is hosted by ductile-brittle faults within Archean metamorphic core complex. The deposit is characterized by gold-bearing quartz-polymetallic sulfides veins. The Mapeng granitoids stock and intermediate-basic dikes intruded the metamorphic basement rocks, and are spatially related to gold mineralization. Detailed laser ablation inductively coupled plasma mass spectrometry （LA ICP-MS） U-Pb zircon ages of the granitic rocks, dykes and mineralized quartz veins in the studied area reveal its magmatic and mineralized history. The mineralized quartz veins contain inherited zircons with ages of about 2.55 Ga and 1.84 Ga, probably coming from the basement. These two Precambrian events are coeval with those in other parts of the NCC. The Mapeng granitoid stock, the largest intrusion in the area, was emplaced at ca. 130 Ma, and is coeval with magmatic zircon populations from diorites and quartz diorite pophyrites in the same region. The ca. 130 Ma magmatism and gold mineralization were most likely related to an underplating event that took place in the Taihang orogen at Late Mesozoic. The timing of gold mineralization with respect to felsic magmatism in the area is similar to those observed in other major gold-producing provinces in the NCC. This episode is simultaneous with those in the eastern margin of NCC, indicative of a widespread late Yanshanian metallogenic event that was a response to the Early Cretaceous lithosphere in the eastern NCC, in which the mesothermal gold deposits were formed from similar tectono-magmatic environments.

Metallogenic‘factories’and resultant highly anomalous mineral endowment on the craton margins of China

The current margins of the North China and Yangtze Cratons provide arguably the best examples globally of anomalously high mineral endowment within a 100 km buffer zone,hosting 66 diverse world-class to giant ore systems that help explain China’s premier position as a producer of multiple metal and mineral commodities.After the cratonization of these crustal blocks during the Neoarchean-Paleoproterozoic,with incorporation of iron ores on assembled micro-block margins,the margins of the cratons experienced multiple convergence and rifting events leading to metasomatism and fertilization of their underlying sub-continental lithospheric mantle.The rifted margins with trans-lithosphere faults provided pathways for Cu-Au(Mo-W-Sn)-bearing felsic to Ni-Cu-bearing ultrabasic intrusions and REE-rich carbonatite magmas,and for the development of marginal sedimentary basins with both Cu-Pb-Zn-rich source units and reactive carbonate or carbonaceous host rocks.There was diachronous formation of hydrothermal orogenic gold,antimony,and bismuth systems in the narrow orogenic belts between the cratons.Complexity in the Mesozoic Paleo-Pacific subduction systems resulted in asthenosphere upwelling and lithosphere extension and thinning in the North China Craton,leading to anomalous heat flow and formation of orogenic gold deposits,including those of the giant Jiaodong gold province on its north-eastern margin.These gold deposits,many of which formed from fluids liberated by devolatilization of previously metasomatized sub-continental lithospheric mantle,helped propel China to be the premier gold producer globally.The thick sub-continental lithospheric mantle of the cold buoyant cratons helped the preservation of some of the world’s oldest porphyry-skarn and epithermal mineral systems.Although craton margins globally control the formation and preservation of a diverse range of mineral deposits,China represents the premier example in terms of metal endowment due to the anomalous length of its craton margins combined with their abnormally complex tectonic history.

Geochronology and geochemistry of the five magmatic rocks in the Ningzhen region,China

The Ningzhen region of China is located in the easternmost part of the middle-lower Yangtze River Cu–Fe polymetallic metallogenic belt. From west to east, it comprises five main intermediate–acidic intrusive complexes: the Qilinmen, Anjishan, Xiashu–Gaozi, Shima, and Jianbi complexes. Geochemical investigations show that these five intrusive complexes exhibit high contents of SiO_2, at 64.74–73.40 wt%, Al_2O_3, at 14.15–17.37 wt%, and K_2O + Na_2O, at 6.49–8.68 wt%. The majority of the samples belong to the high-K calc-alkaline series, with a few samples plotting in the calc-alkaline and tholeiitic series. Trace element analysis shows that the samples are enriched in large ion lithophile elements(LILE) and are depleted in high field strength elements(HFSE).The chondrite-normalized rare earth element(REE) patterns are characterized by right-inclined curves, showing light rare earth element(LREE) enrichment. In addition,the(La/Yb)Nratios are high at 15.02–37.28, with an average of 29.13, and slightly negative or none Eu anomalies are present. In the(La/Yb)N–d Eu diagram, the samples plot within the crust-mantle type field. Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) zircon U–Pb dating yielded ages of122.0 ± 1.0 Ma, 106.1 ± 0.8 Ma, 108.7 ± 1.4 Ma,103.5 ± 1.9 Ma, and 96.8 ± 1.7 Ma for the Qilinmen,Anjishan, Xiashu–Gaozi, Shima, and Jianbi complexes,respectively. On the basis of this research and knowledge of several known metal deposits related to these complexes, we suggest that the Mesozoic large-scale diagenesis and metallogenesis in the Ningzhen region may have ceased at 100 Ma or about 95 Ma.

Jurassic Intra-plate Basaltic Magmatism in Southeast China:Evidence from Geological and Geochemical Characteristics of the Chebu Gabbroite in Southern Jiangxi Province

Geochemical and isotopic investigations have been carded out on the Chebu gabbroite in southern Jiangxi Province, southeast China and these results are compared with gabbro bodies along the coast of Fujian Province in order to understand their magma sources and tectonic implications. The Chebu intrusion formed at the beginning of the Middle Jurassic （172~4.3 Ma）. These rocks are Ti-rich and Al-poor in major elements, characterized by strong enrichment in large-ion lithophile elements （LILE） and moderate enrichment in high field strength elements （HFSE） and light rare-earth elements CLREE）, without pronounced Nb or Ta anomalies. Age-correlated Sr-Nd isotope ratios show moderately high ranges of （^87Sr/^86Sr）i from 0.7065 to 0.7086 and 0.5124 to 0.5125 of （^143Nd/^144Nd）i. The geochemical characteristics of the Chebu gabbroite suggest that it is notably different from island-arc basalt and similar to intra-plate basaltic rocks. By combining interpretations of its geological and geochemical characteristics and the regional geological development history, the Chebu gabbroitic intrusion is thought to be the product of asthenosphere upwelling and rapid lithosphere extension during a transition of tectonic systems in southeast China. The tectonic environment and source characteristics of the intrusion are different from Cretaceous gabbro bodies along the coast of Fujian Province, The former formed in a tectonic environment of rapid intra-plate lithospheric extension and the source characteristics were of a weakly enriched primitive mantle, whereas the latter originated mainly in a volcanic-magmatic arc extensional tectonic environment and the nature of the source was an enriched mantle with more subduct subducted components.

Genesis of Makeng-type Fe-polymetallic deposits in SE China:New constraints by geochronological and isotopic data from the Dapai–Makeng metallogenic system

The southwestern Fujian depression belt(SFDB)is an economically important Mesozoic Fe metallogenic belt in South China and is renowned for its Makeng-type Fe deposits,in which stratified skarn Fe orebodies generally occur in or near the contact zone between late Paleozoic carbonate sequences and Mesozoic granites.However,the genesis and geodynamic setting of these deposits remain unclear because the characteristics of the widely distributed Pb–Zn–Cu and Mo orebodies in these deposits and the temporal,spatial,and genetic relationships between magmatism and mineralization are poorly defined.The Dapai Fe polymetallic deposit in the SFDB is a typical example of Makeng-type Fe deposits but also has regional significance,whereby the stratified skarn Fe orebodies have overprinted the stratabound Pb–Zn–Cu mineralization followed by final fissure-filling by vein-disseminated Mo mineralization.A detailed geological investigation suggests that episodic magmatic–hydrothermal events were involved in the formation process of the Dapai Fe polymetallic deposit.Pyrite and sphalerite from the Pb–Zn–Cu orebodies yield an Rb–Sr isochron age of 175.5±3.3 Ma,which is regarded as the timing of Pb–Zn–Cu mineralization.Zircon grains from Fe-mineralized granodiorite porphyry and Mo-mineralized monzogranite yield weighted-mean 206Pb/238U ages of 146.3±0.9 Ma and 131.7±0.4 Ma,interpreted as the timings of Fe and Mo mineralization,respectively.Six zircons from granodiorite also yield a 206Pb/238U model age cluster of184 Ma,which coincides reasonably with the timing of Pb–Zn–Cu mineralization and implies the existence of an unidentified ore-related intrusion in the Dapai deposit.Five further zircons from the porphyritic granodiorite yield an age cluster of-150 Ma,consistent with the timing of Fe mineralization.Galena,pyrite,and sphalerite from the Dapai and Makeng deposits have similar S–Pb isotopic compositions and suggest a magmatic source.Combining our results with published isotopic data for the SFDB,we suggest that the Pb–Zn–Cu mineralization in this area was derived from crustal magmas that mixed with mantle-derived magma prior to emplacement.The d56Fe and d57Fe values of magnetite from Dapai and Makeng are both slightly lower than those of the orerelated granites,suggesting that Fe in the initial fluid in both deposits was derived mainly from coeval granitic rocks.The Fe isotopic variation between intrusions and skarn Fe orebodies is interpreted as resulting from mass fractionation that occurred during fluid exsolution from melt.Contents of Re in molybdenite from published data for the SFDB indicate crust–mantle mixed sources of Mo and Re.The Makeng-type Fe polymetallic deposits formed as a result of three magmatic–hydrothermal episodes,generating Pb–Zn–Cu mineralization at 185–160 Ma,Fe–Mo mineralization at 150–140 Ma,and Mo–Fe mineralization at 135–130 Ma.The different metal associations formed during multiple stages of magmatism caused by ongoing subduction and rollback and/or retreat of the paleo-Pacific Plate.