Indosinian Foreland Fold-and-Thrust Belt Bordering Yunnan and Guangxi, China

Recent discoveries of ophiolites indicate that there must be a Palaeotethyan geosuture zone bordering China and Vietnam, which separates the Vietbac block from the South China subcontinent. The Indosinian foreland fold-and-thrust belt bordering Yunnan and Guangxi provided further evidence for the palaeotethysides. The oceanic crust was subducted southwestwards while the magmatic arc migrated northeastwards, and the continent-arc collision occurred in the Late Triassic with the thrusting being extended towards the north or northeast. The features of thrust-nappe structure are discussed, which proved the continental margin of the Palaeotethyan ocean there to be a complicated one. A face-to-face collision occurred first along the NW-striking segment and then along the ENE-striking segment accompanied by transpression or oblique thrusting occurring along the NW-striking one.     

Genesis and Main Differences of Jiama and Qulong Super-Large Depoist in Gangdese Metallogenic Belt

Please refer to the attachment(s) for more details     

Ordovician and Silurian lithofacies and base‐metal deposits of the Lachlan Fold Belt

Two lithofacies maps of the Lachlan Fold Belt, one for the Ordovician and one for the Silurian, are illustrated. Both maps indicate shorelines in western New South Wales, Victoria and Tasmania.

The Ordovicoan map suggests open‐sea conditions eastwards from the shoreline with one major and two minor andesitic volcanoes (or volcanic centres). The Silurian map suggests segmentation of the Lachlan Fold Belt into the Melbourne Basin, Omeo Land, Newell Basin, and Budawang Land. The Newell Basin displays a nearshore (Louth‐Mitta Mitta) coarse clastics facies and an offshore (Wellington‐Cooma) platform carbonate facies. Acid volcanism was widespread over the Newell Basin in Silurian time, but did not occur in the Melbourne Basin.

The Louth‐Mitta Mitta and Wellington‐Cooma facies boundary coincides with the position of the Coolac‐Honeybugle Serpentine Belt and the outcrop area of the Girilambone Beds, suggesting that these features were already in some way prominent during the Silurian Period: the Serpentine Belt may have been a fault, and the Girilambone Beds may have been land.

The origin of base‐metal deposits in the Silurian rocks is thought to be somehow related to the heat generated in the subsurface during Silurian time as is indicated by the volcanism and granite intrusion; and also to the fact that the deposits occur in a transgressive sequence which contains the first phase of acid volcanism in the known geological history of the Lachlan Fold Belt.     

Volcanism in Sanjiang Tethyan Orogenic Belt:New Facts and Concepts

Sanjiang area in Southwestern China is tectonically sit-uated at the east end of Himalaya-Tethys tectonic do-main and at the conjunction of Tethyan MountainChain and Circum-Pacific Mountain Chain.It is one ofthe key areas to understand the global tectonics and alsoone of gigantic metallogenic provinces in China and evenin the world.Volcanism had occurred during the periodof time from Proterozoic to Cenozoic.The most impor-tant and active periods of volcanism,however,areCarboniferous,Permian and Triassic.The pattern ofspatial distribution of Sanjiang volcanic rocks andophiolites can essentially be described as that severalintra——continental micro-massif volcanic districts arerespectively sandwiched between each two of four couplingophiolite—are volcanic belts,which are successively fromwest to east:Dingqing-Nujiang belt,Laneangjiangbelt,Jinshajiang belt and Ganzi-Litang belt.Fourtectono-magmatic types of volcanic rocks have been recognized in Sanjiang area as follows:mid-ocean-ridge/para-mid-ocean-rid     

Geobarmal Gradient in Orogenic Belt and Metamorphism Caused by Ultrahigh Pressure

The components and structures of lithosphere,inhomogeneous,are changing incessantly in different periods.Therefore,the state of load,called the pressure,in lithosphere is also incessantly changing.When the lithosphere volume remains the same,namely on the premise of isovolumes,the geobarmal gradient is:(dp/dh)v=(p/(e)h)v (p/(e)T)v(dT/dh)v.If β=(dp/dh)v/(p/(e)h)v is supposed,then β=1 rg-1Cv (dT/dh)v.When the geothermal degree in (dT/dh)v is zero,then the pressure grade of lithosphere is equal to the lithostatic grade,which is the minimum value in the pressure grade of lithosphere.Suppose that the lithosphere is made only up of quartz,Cv≌Cp=0.782 5.718×10-4 T-1.883×104T-2 (J·g-1·K-1) is obtained,which is the minimum one in lithospheric rock,and then the geothermal grade value of 20 ℃/km is calculated according to the geophysical transection data of Qinling Mountain orogeny.The results show that the high-pressure and ultrahigh-pressure eclogites in Jiangsu Province and Huangzhen,Dabie may,on the condition of incompletely isovolumes,occur in the depths of 17-40 km with the increase in geothermal temperature,whose values of β do not correspond to the theoretic value of 3.08.     

Deformation Characteristics and Tectonic Evolution of the Eastern Qinling Orogenic Belt

The Qinling Mountains separating the northern from the southern China plate is a key region for the study of structural evolution of eastern Asia. It is composed of the Palaeozoic fold belt in its northern part and the Variscan and Indosinian fold belts in its southern part. The evolution of the former is marked by the closure of a northward subducting oceanic basin in the early stage, followed by southward obduction of ophiolites and intracontinental thrusting during the Variscan; whereas that of the latter is represented by intracontinental, shallow crustal deformation on the basis of a large-scale detachment structure(with a horizontal slip of at least of 100 km). Since the late Palaeozoic, however, both of the belts have been cut by a series of east-west sinistral strike-slip faults.     

High-Pressure and Ultrahigh-Pressure Metamorphic Belt in Tongbai-Dabie Mountains,Central China

There are four units of high-pressure to ultrahigh-pressure metamorphism extending from south to north across the Tongbai-Dabie Mountains: the epidote-blueschist-facies unit, the low-temperature eclogite facies unit , the ultrahigh-pressure eclngite facies unit and the medium-temperature eclogite facies unit . The later two units were formed during the Caledonian subduction between the Tongbai-Dabie microplate and the North China plate ,the former two units are the products of Indosinian continental-continental subduction and collision between the Yangtze and the North China plates.     

Fluid Activity and Tectonic Evolution in the Northern Qilian High-pressure Metamorphic Belt

The Northern Qilian high-pressure metamorphic belt has experienced multiple deformation-metamorphism, which consists of at least four stages.In 550.8-526 Ma, eclogites were formed. High temperature and pressure caused the escape of a large quantity of gas-liquid fluids from rocks while silicate melt was generated. In the late stage, small amounts of CO2 and H2O infiltrating along fractures were introduced.In the formation of glaucophane schist (447-362 Ma), devolatilization reactions were dominated during the subduction-uplift stage of the paleoplate.In the uplift-exhumation stage (400-380 Ma) the increase of internal space of fractures in the rocks favoured fluid infiltration and concentration. These fluids participated in hydration reactions in the retro-metamorphism. The fluids participating in the mineral reactions have the compositions of CaCl2-NaCl-H2O.In subsequent thrusting (<380 Ma), the metamorphic terrain was uplifted to the shallower crust and ductile-shearing deformation took place, which c     

Classification and Type Association of Tin Deposits in Southeast Yunnan Tin Belt

Pneumato-hypothermal to meso-epithermal tin-polymetallic(W, Be,Bi,Mo,Cu,Pb,Zn and Ag) deposits ,dominated by cassiterite-sulfide type and cassiterite-quartz type,are extensively developed around granite intrusives in the Southeast Yunnan Tin Belt genetically related to Yenshanian tecto-magmatism.Thd deposits are grouped into two classes,four associations and fourteen type according to the classification scheme proposed by the author to reflect their geological and genetic characteristics as well as economic implications.The deposits are arranged in an appar-ent zonal pattern from the granite body outwards in terms of “association“(cassiterite-feldspar→cassiterite-quartz→cassiterite sulfide),typical ore-forming metals(Sn-W-Be-Mo-Nb-Ta-Tr→Sn-W-Cu-In→Sn-Pb-Zn-As-Cd),and formation conditions(pneumato-hypothermal→hypothermal-mesothermal→mesothermal-epithermal),although such distribution pattern may be more or less complicated by local specialities of granit4 petrochemistry,host rock lithology and structure.     

Water Security and the Countermeasures in South Asia Based on the “Belt and Road” Initiative

South Asia is the subregion of Asia with the most neighbors of China. Although the high mountains in the Great Himalayas spatially separate South Asia from East Asia along the border of China’s autonomous region of Tibet, the geographical items such as mountains and rivers link the countries in South Asia with China, resulting in a special and complex geopolitical environment and relationship. In this geopolitical relationship, the transboundary rivers are becoming a key issue of this region in an era of increasing water stress. Depleted and degraded transboundary water supplies have the potential to cause social unrest and spark conflict within and between countries in South Asia, and complicate the geopolitical relationship among them. In addition, the increasing impacts from climate change and human activities will definitely bring many transboundary eco-environmental issues in this region, projecting a big challenge to regional stability and development. The key issues related to the water resources supplement and exploration require the transboundary rivers to be a positive role in regional water resources utility and exploration, and the result will definitely affect regional relationship and water security. How to handle these issues and challenges will be a question for the countries in this region with a long time. Currently, the “Belt and Road” Initiative represents an opportunity to build a shared vision for common prosperity through regional cooperation and is a way to inject new positive energy into world peace and development. In the light of this, the countries with transboundary rivers in South Asia must come together to construct a cooperative mechanism of water security, and adopt a win-win cooperation for the use of transboundary rivers under the principles of “equal”, “equitable” and “reasonable”.     

Crustal Texture and Rheological Evolution of Tongbai－Dabie Orogenic Belt，China

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Geological and Geochemical Characteristics and Petrogenesis of the Anqing—Lujiang Quartz Syenite Rock Belt,East China

The Anqing-Lujiang quartz syenite rock belt consists of the Huangmeijian, Chengshan and Dalongshan composite batholiths which intruded into the Mesozoic strata. The country rocks were subjected to thermal contact metamorphism with little sign of folding and regional metamorphism. The rock belt is Late Yenshanian in age with a Rb-Sr isochron age of 135 Ma. Major rock types are quartz syenite and, to a lesser extent, syenite porphyry and alkali feldspar granite. Rock-forming minerals are dominantly potash feldspar (more than 50%) and lesser amounts of plagioclase and quartz. Mafic minerals, mostly Mg-biotite with lesser amounts of amphibole and pyroxene, are rare. Occasionally, alkalic mafic minerals (aegirine, riebeckite) are found. Characteristic accessary minerals of the earlier intrusives are magnetite, sphene and apatite and those of the later intrusives are ilmenite and zircon. Typologic distribution and evolutionary trend of zircon population are very similar to those of granites of mantle origin as suggested by Pupin, J. P. Petrochemically, the rock belt is poor in Ca but rich in alkali and Al with Na₂O+K₂O > 10%. It belongs to the K-Na transitional series, with a high alkalinity ratio (A. R. = 3–7) and a K /Na (atom) ratio close to unity. Rocks in the belt are rich in REE which tends to decrease from the early to the late stage, belonging to LREE type. The initial Sr ratio is 0.7078–0.7064. The rock belt is the Mesozoic anorogenic product of alkalic magmatic activity from a deep-seated source. According to a mantle-crust mixing model for Sr and Pb isotopes, it is estimated that 60.2–53.8% of the materials has been derived from the mantle. Additionally, its rich alkali, poor water content and anorogenic characteristics suggest that the belt is similar to the A-type granites.     

Tectonic Evolution of Tertiary Basins in circum-Pacific Belt of China and Their Geodynamic Setting

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Relationship between the TanLu Fault and Dabie Orogenic Belt in Eastern China

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Polyphase Tectonic Events and Cenozoic Basin-Range Coupling in the Tianshan Belt, Northwestern China

Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision     

Geochemical Types of Granitoids of the Mongol—Okhotsk Belt and Their Geodynamic Settings

The following geochemical types of granitoids have been investigated in the Mongol-Okhotsk belt:tholetitic,palingenic calc-alkaline,latitic,plumasitic and arpaitic rare-metal granites.Plagiogranites of the tholeiitic series occur within the Mongol-Okhotsk suture,indicating a subduction environment.The calc-alkaline granitoids responsible for the batholith-like intrusions and their formation are related to collision environments.The latest granitoids of the latite series and rare-metal granites came into existence after the collision of continental masses,providing evidence of intraplate magmatism.     

Isotopic Ages of the Penglai Group in the Jiaobei Belt and Their Geotectonic Implications

The Penglai Group in the Jiaobei Belt is the only remaining cover of the Archaean to Early Proterozoic crystalline basement in eastern Shandong. The ages of deposition of the Penglai Group and of its deformation and metamorphism have long been a subject of speculation. Whole-rock Rb-Sr ages, illite-whole-rock pair Rb-Sr ages and illite K-Ar ages recently obtained from the Penglai Group slates are reported and interpreted in this paper. On the basis of structural and metamorphic studies coupled with analyses of illite crystallinity, XRD and SEM , a whole-rock age of 473±32 Ma (Ordovician) is interpreted as the time of termination of burial metamorphism experienced by the Penglai Group. Therefore, the age of the Penghai Group is older than Ordovician. The first-phase folding and syntectonic low greenschist facies metamorphism in the Penglai Group, i.e. the Penglai Movement, took place before 299±4 Ma B.P., i.e in the Late Carboniferous. The Penglai Movement that occurred in the Jiaobei Belt on the south     

Geology and Genesis of Peraluminous Granites in East Tianshan Upper Paleozoic Island Arc Belt

A peraluminous granite belt occurs along the connecting zone between the Turpan-Hami Precambrian block and the Upper Paleozoic island arc belt. Muscovite granite and twomica granite are the essential lithological components of that belt. All the potassium feldspars in these granites are microcline. Heavy minerals are dominated by magnetite. SiO₂ contents of these granites are greater than 73% with most of the A/NKC values greater than 1.1, normative corundum values greater than 1. Plots of CIPW norms in the (Al-K-Na)-Ca-(Fe²⁺+ Mg) diagram are mostly situated in the plagioclase-cordierite-muscovite region. The rocks are characterized by very low contents of minor elements and ΣREE with strong Eu depletion, δ¹⁸O values between 6.6‰ and 7.0‰, Rb-Sr isochron age of 260.2 ± 6.2 Ma and an initial⁸⁷Sr/⁸⁶ Sr ratio of 0.7052. These granites might have been produced by partial melting of moderately acidic volcanites and low-maturity sediments in the basement sequences and could be genetically connected with the southward A-type subduction of the Turpan-Hami block following the closure of the Middle Carboniferous back-arc basin.