Abstract:Western Tianshan Orogen, located in the conjunction of the Kazakhstan-Junggar Plate and the Karakum-Tarim Plate, has been regarded as the collision zone and metallogenic zone consisting of a series of Precambrian blocks, Paleozoic oceanic crust, and continental marginal arcs. The study of the orogenic-metallogenic processes of western Tianshan Mountain have received extensive attention. In this paper, the authors established the tectonic framework of western Tianshan Orogen in the Paleozoic on the basis of the tectonic division, and proposed a five-stage model of the tectonic evolution in Paleozoic:Rodinia supercontinental breakup and the formation of the early Paleozoic archipelagic ocean in northern Tianshan Mountains (Z-O₂), closure of the early Paleozoic archipelagic ocean in northern Tianshan Mountains and the incipience of the southern Tianshan oceanic basin (O₃-S), formation and development of the northern and southern Tianshan oceanic basins in the late Paleozoic (D-C₁), closure of the northern and southern Tianshan oceanic basins and the subsequent formation of Tianshan orogenic belt (C₁-C₂) and, finally, the post-collision stage of the intraplate environment (C₂-P).

Abstract:Gold is a dominant mineral species in South America, whose importance is only second to that of copper. According to gold reserves statistics from the USGS, the gold reserves were 2800 tons in Peru and 2400 tons in Brazil in 2016, and 3900 tons in Chile in 2014. The main 31 large and superlarge gold deposits were comprehensively studied in this paper on the basis of the geological background analysis of gold deposits in South American Andean metallogenic belt and South American platform. The spatial and temporal distribution and geological characteristics of gold deposits, such as porphyry copper-gold deposits, epithermal gold deposits, IOCG gold deposits, and orogenic gold deposits, were analyzed in detail. The authors rearranged the characteristics of the metallogenic region and found out the relationship between regional tectonic magmatic and mineralization evolution, with the purpose of providing scientific basis for future exploration and exploitation of gold mines in South America. In the Andean metallogenic belt, the gold mineralization was closely related to the subduction of the Pacific plate to the South American Plate. The large and superlarge gold deposits are mainly porphyry copper-gold deposits, epithermal gold deposits, IOCG gold deposits and so on. The main gold mineralization is concentrated in the new generation, forming a number of famous gold deposits in the world. In the South America platform,the gold metallogenic belt is located at the edge of the Amazonian block and was influenced by the Trans-Amazonian cycle in Paleoproterozoic (2.5-1.8 Ga), which had undergone repeated subduction and orogeny. The large and superlarge gold deposits are main orogenic gold deposits. The metallogenic period is mainly the Archean-Late Proterozoic period. The gold resources are quite rich in South America, and it has great potential for exploration and exploitation in the future.

Abstract:The Tethyan domain hosts the world's most abundant Mississippi Valley-Type (MVT) Pb-Zn deposits, which occur in fold-thrust belts and forelands on both sides of the continent-continent collisional zone through the whole Tethyan domain. Mineralization commonly took place when the ore districts were experiencing strike-slip or extensional deformation, which occurred after regional compression or during the late stage of a compressional deformation event. The main ore-controlling factors include extensional faults, evaporite diapir, carbonate dissolution and collapse, evaporite dissolution and collapse, porous dolostone, and barite-bearing strata. Records of hydrocarbon fluids are present in many Pb-Zn deposits and ore districts of the Tethyan domain. They reacted with (dissolved) sulfate to provide reduced sulfur for the ore formation. The generation of such abundant MVT Pb-Zn deposits in the Tethyan domain can be attributed to the continent-continent collisional tectonic setting, large amounts of evaporites, and plentiful hydrocarbon fluids. This study raises the exploration potential for MV TPb-Zn deposits in the Tethyan domain.

Abstract:South America is rich in iron ore resources, which are characterized by widely distributed world-class iron deposits, high grade of orebodies, and a variety of deposit types. An analysis of tectonic framework of South America shows that the most important types of iron deposits include sedimentary metamorphic type which is distributed in cratonic shield area and its edge, and volcanic origin type which is distributed in Andean coastal orogenic belt. The former mainly formed in the Archean Proterozoic, whereas the latter mainly formed in Mesozoic and Cenozoic. The results of comprehensive studies show that 10 important iron metallogenic zones can be delineated:Bolivar iron zone of Venezuela, Amapa iron zone of Brazil, Para iron zone of Brazil, Minas gerais iron zone of Brazil, Rio Grande do Norte iron zone of Brazil, balaiba iron zone of Brazil, Bahia iron zone of Brazil, Mato Grosso do Sul iron zone of Brazil, Santa Cruz iron zone of Bolivia, Ika-Arequipa iron zone of Peru, and Calama-Santiago coastal iron zone of Chile. Based on an analysis of typical deposits in important metallogenic zones and statistical analysis methods, the authors have summarized the temporal and spatial distribution regularities of iron mineralization in South America with the purpose of providing references so as to find more iron ore resources in this area in the future.

Abstract:The Cretaceous is an important period in which occurred many geological events, especially the OAEs (Oceanic Anoxic Events) characterized by black shales, and theoxic process characterized by CORBs (Cretaceous Oceanic Red Beds). This paper describes the causative mechanism which explains how the oceanic environment changed from anoxic to oxic in Cretaceous. Two typical events show different results that caused by interactionsoftheEarthSpheres. Here we propose that the rise of atmospheric CO₂ occurred because the enhanced submarine volcanism-was abruptly and permanently diminished during the Cretaceous. The Cretaceous large-scale submarine volcanism caused the concentration of CO₂. The releasing of the inner energy of the lithosphere and thedistribution oflandwhich caused the increasing of atmospheric temperature. This change presented the same trend as the oceanic water temperature, and caused the decreasing of O₂ concentration in the Cretaceous ocean, and then the OAEs occurred. The lithosphere produced volume of lava in the upper oceanic crustwhich contained Fe in the seafloor. When thehydrothermal fluids alteration of oceanic crust and the seawater/basalt interactions (including microbes alteration of submarine basaltic glass), the element Fe dissolved in seawater. Iron is a micronutrient essential for the synthesis of enzymes required for photosynthesis in oceanic environment, it could spur phytoplankton growth rapidly. The photosynthesis of phytoplankton which can consume carbon dioxide is in much of the world's oceans, wherever they are in atmosphere or in ocean. This process could produce equal oxygen. And then, the oxic environment characterized by red sediment which is rich in Fe³⁺ appeared. The data show rhythm of the anoxic and oxic from south Tibet and DSDP/ODP section, which the anoxic is often accompanied by the occurrence of oxygen rich environment.Undoubtedly, the anoxic andoxic in the Cretaceous Ocean were controlled by the mutually dependent processes of the Earth system which included lithosphere, hydrosphere, atmosphere and biosphere. An important conclusion of this study is that the black shalesand the oceanic red beds are caused by the same reason, but led different results. The anoxic and oxic in the Cretaceous ocean were caused by volcanic activities, but they were of different causative mechanisms. The former was based on physical and chemical process, while the latter involved more complicated bio-oceanic-geochemistry process.

Abstract:Located in the central part of Pamir, Tajikistan, near the Rushan-Pshart suture zone, the Murgab pluton separates the middle Pamir from southern Pamir. Petrologically, the pluton consists of gabrro and diorite which intruded into the epimetamorphic detrital rocks of late Proterozoic (?). LA-ICP-MS zircon U-Pb dating shows that the age of gabbro and that of diorite is 232±1.5 Ma and 231.5±1.9 Ma respectively, which represents the formation age of this pluton. The ε_Hf (t) values of the zircon are in the range of 4.8-12.1 and 6.4-10, with a weighted average of 8.1±1.5 (MSWD=6.5) and 7.9±0.8(MSWD=2.4), suggesting that its original rock was derived from mantle materials. The one-stage Hf model ages (T_DM1) are 477-621 Ma, 391-672 Ma respectively indicating an original rock of Cambrian-Precambrian basement. The lithogeochemical data shows that gabbros are characterized by rich Mg and, poor Al and alkali, thus belonging to low-potassium rocks, whereas the diorites are rich in Si, Al and poor in Mg, Ti, hence belonging to calc-alkaline to high K calc-alkaline rocks. The gabbros and diorites share similar REE and trace elements features, which are characterized by high total REE content and rich LREE with slight normal Eu anomaly. The trace elements are characterized by rich LILEs and poor HFES. Based on geochemical characteristics, the authors infer that the pluton formed in an island-arc environment. The subduction was continuing during late Triassic, which indicates that the Rushan Ocean basin was closed at least later than 232 Ma.

Abstract:At present, there are many different interpretations for the genesis of the vanadium-titanium magnetite deposits in the mafic-ultramafic complex, which has to a certain extent caused confusion to the resource exploration of these deposits. Therefore, it is very important to discuss the mechanism of large-scale aggregation of ore-forming minerals in mafic-ultramafic intrusion. The Zhaka rock mass in the Alaotra Lake area of the northeast of Madagascar is a typical mafic layered intrusion with a very large vanadium-titanium magnetite deposit. The Shenyang center of CGS has found the vanadic titianomagnetite deposit with 800 million tons of iron ore (including 333),associated with 60 million tons of Ti and 2.3 million tons of V. These results provide a good condition for clarifying the genesis of the vanadium and titanium magnetite deposit. This paper reports the geology, orebody geology, petrography, mineralogy and petrological geochemical characteristics of the Zhaka rock mass. The main conclusions are as follows:(1) The rhythmic layering is a typical mafic layered rock mass, whereas the pegmatite can form an independent invasive unit; (2) orebodies mainly occur in the layered rock mass, and can be divided into three different types, i.e., integrated type, unconformity type and pegmatite type; (3) gabbro has the crystallization sequence of olivine → plagioclase → clinopyroxene or olivine → plagioclase + clinopyroxene, suggesting that the Zacha rock mass is a shallow stratigraphic rock mass, with the emplacement depth of~3 km; (4) ore mineral and silicate minerals are thermodynamically unbalanced and shared with water-dark mineral minerals, suggesting that mineralization occurred in the rich volatiles in the late magma evolution; (5) The REE quadruple effect of dense massive iron ore also indicates that the mineralization process was accompanied by fluid activities of F, Cl and other components. It is held that the formation of vanadium-titanium magnetite deposit in the Zacha rock mass was related to the process of the magmatic fluid.

Abstract:The Chambishi copper mine in Zambia is located in the central Africa copper-cobalt metallogenic belt. The bedded orebodies occur in the Neoproterozoic sandshales of Roan Formation. The Roan Formation unconformably overlies the Early Proterozoic sandy conglomerate of Muwa System, which in turn overlies the lower Chambishi granite basement. U-Pb zircon dating yielded the age of 1984 ±6-1986 ±6 Ma for Chambishi granite, and the upper age limit is 1932 ±8 Ma for Muwa System. The lithogeochemistry and chondrite-normalized REE patterns of Chambishi granites have the characteristics of S-type granites. Combined with the data of regional geological evolution, the authors believe that Archean Congo craton may have experienced activation over a large area during Early Proterozoic period, and a stable ancient block had been formed in the Early Proterozoic period.

Abstract:The world's most important and older Archaeozoic metamorphic basement is exposed in Carajas province of Brazil, it is known as one of the metallogenic provinces that have most abundant ore deposit types and highest extent of resource aggregation. Its basement of Xingu complex is the Southern American Craton's older Archaean greenstone-gtanite body. Based on the investigation of geological features of the basement complex, the authors studied the chronology of metamorphic pluton that intruded into the metamorphic basement and put forward the understanding concerning composition, structure and tectonics of the basement complex. It is thought to be the ancient metamorphic basement with granulite-amphibolite facies gneisses and complex as the main body. The authors peeled off the charnockite and tonalite-trondhjemite granitic gneiss and further decomposed the metamorphic intrusions in different periods. The LA-ICP-MS ages of zircons in (2899±45) Ma, (2742±9.5) Ma and (2831±19) Ma were acquired in gneissic granite, and this further confirms the fact that the age of Xingu complex is Mesoarchean within 3.05-2.85 Ga, and the Xingu complex also includes two tectonic periods of supracrustal rock and gneiss suite with age of 3.05-2.96 Ga and 2.96-2.85 Ga.

Abstract:Zhuguangshan granitic composite batholith situated in Hunan-Jiangxi-Guangdong border area is an important part of Nanling large granite province, with the total area of northern and southern body being greater than 5000 km². The results of zircon SHRIMP U-Pb geochronology of granitoids of northern Zhuguangshan show that the granitic body was formed in three periods with ages varying from the Caledonian through Indosinian to Yanshannian. Caledonian granodiorite was formed in late Silurian period, Indosinian biotite adamellite was formed in late Triassic period and Yanshannian dimicaceous adamellite was formed in late Jurassic period, with SHRIMP zircon U-Pb ages being (414.5±4.5) Ma, (417.3±4.8) Ma, (207.5±2.7) Ma, and (148.2±1.7) Ma respectively. The results obtained by the authors provide important geochronologic basis for the study of geology and mineralization in this area.

Abstract:The Dushan antimony ore concentration area in Guizhou Province is one of the most important Devonian antimony metallogenic regions. It has superior ore-forming geological conditions and abundant mineral resource. In the Dushan antimony ore concentration area,1 large, 2 middle, 5 small and 13 antimony ore spots have successively been found. Based on antimony metallogenic conditions, geochemical anomaly, geophysical anomaly and remote sensing image interpretation, the authors summarized exploration indicators of strata and lithology, tectonic, alteration, geochemistry, remote sensing and geophysics. In the prospecting toward the deep subsurface of the the Banpo antimony deposit in Dushan County, the authors used exploration indicators of metallogenic fault, closed high resistance body of geophysical anomaly from CSAMT geophysical anomaly, drilled engineering validation holes, found a new concealed rich antimony orebody, and achieved a deep concealed ore prospecting breakthrough. In the comprehensive study of various kinds of abnormal information and on the basis of exploration marks, the authors delineated and optimized the three prospecting target area of Banpo periphery, Nongjiang-Guixiu-Jiabai-Beida and Weizhai areas. In the course of ore comprehensive prospecting in the future, it is expected to achieve new prospecting breakthrough through optimization and integration of detection technologies and new evaluation of the old mine.

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