The ore deposits of the Mesozoic age in South China can be divided into three groups, each with different metal associations and spatial distributions and each related to major magmatic events. The first event occurred in the Late Triassic (230–210 Ma), the second in the Mid–Late Jurassic (170–150 Ma), and the third in the Early–Mid Cretaceous (120–80 Ma). The Late Triassic magmatic event and associated mineralization is characterized by peraluminous granite-related W–Sn–Nb–Ta mineral deposits. The Triassic ore deposits are considerably disturbed or overprinted by the later Jurassic and Cretaceous tectono-thermal episodes. The Mid–Late Jurassic magmatic and mineralization events consist of 170–160 Ma porphyry–skarn Cu and Pb–Zn–Ag vein deposits associated with I-type granites and 160–150 Ma metaluminous granite-related polymetallic W–Sn deposits. The Late Jurassic metaluminous granite-related W–Sn deposits occur in a NE-trending cluster in the interior of South China, such as in the Nanling area. In the Early–Mid Cretaceous, from about 120 to 80 Ma, but peaking at 100–90 Ma, subvolcanic-related Fe deposits developed and I-type calc-alkaline granitic intrusions formed porphyry Cu–Mo and porphyry-epithermal Cu–Au–Ag mineral systems, whereas S-type peraluminous and/or metaluminous granitic intrusions formed polymetallic Sn deposits. These Cretaceous mineral deposits cluster in distinct areas and are controlled by pull-apart basins along the South China continental margin. Based on mineral assemblage, age, and space–time distribution of these mineral systems, integrated with regional geological data and field observations, we suggest that the three magmatic–mineralization episodes are the result of distinct geodynamic regimes. The Triassic peraluminous granites and associated W–Sn–Nb–Ta mineralization formed during post-collisional processes involving the South China Block, the North China Craton, and the Indo-China Block, mostly along the Dabie-Sulu and Songma sutures. Jurassic events were initially related to the shallow oblique subduction of the Izanagi plate beneath the Eurasian continent at about 175 Ma, but I-type granitoids with porphyry Cu and vein-type Pb–Zn–Ag deposits only began to form as a result of the breakup of the subducted plate at 170–160 Ma, along the NNE-trending Qinzhou-Hangzhou belt (also referred to as Qin-Hang or Shi-Hang belt), which is the Neoproterozoic suture that amalgamates the Yangtze Craton and Cathaysia Block. A large subduction slab window is assumed to have formed in the Nanling and adjacent areas in the interior of South China, triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic W–Sn mineralization. A relatively tectonically quiet period followed between 150 and 135 Ma in South China. From 135 Ma onward, the angle of convergence of the Izanagi plate changed from oblique to parallel to the coastline, resulting in continental extensional tectonics and reactivation of regional-scale NE-trending faults, such as the Tan-Lu fault. This widespread extension also promoted the development of NE-trending pull-apart basins and metamorphic core complexes, accompanied by volcanism and the formation of epithermal Cu–Au deposits, granite-related polymetallic Sn–(W) deposits and hydrothermal U deposits between 120 and 80 Ma (with a peak activity at 100–90 Ma).

Major types and time–space distribution of Mesozoic ore deposits in South China and their geodynamic settings

Phanerozoic continental growth and gold metallogeny of Asia

Cretaceous tectonic evolution of South China: A preliminary synthesis

A tectono-genetic model for porphyry-skarn-stratabound Cu-Au-Mo-Fe and magnetite-apatite deposits along the Middle-Lower Yangtze River Valley, Eastern China

The Eastern Qinling region, located in the southern margin of the North China Craton, is characterised by widespread granitoid intrusions Precise geochronological constraints on the age and timing of these intrusions are lacking In this paper, we report SHRIMP zircon U–Pb ages of 12 representative granitoid plutons, together with one syenite stock, dolerite, diorite and granitic dykes in Eastern Qinling The results revealed two main magmatic events, which occurred in the Late Jurassic–Early Cretaceous (158 ± 3 to 136 ± 2 Ma) and the Early Cretaceous (134 ± 1 to 108 ± 2 Ma), respectively The granitoids formed in the early magmatic event are similar in composition and are characterised by a mantle source mixed with variable amounts of crustal components, whereas those resulting from the late-stage magmatism show characters of I-, S- and A-types granite and coexist with coeval dolerite dykes and syenite stocks A similar magmatic age distribution is also recognised in other belts or regions in East China

Late Jurassic–Early Cretaceous granitoid magmatism in Eastern Qinling, central-eastern China: SHRIMP zircon U–Pb ages and tectonic implications

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Spatial-Temporal Distribution of Mesozoic Ore Deposits in South China and Their Metallogenic Settings

Gejiu is the largest polymetallic tin ore-field over the world. Kafang copper deposit is a main copper provider in Gejiu. There are two kinds of ore-body in Kafang copper deposit. One is stratiform-like ore-body, and the other is contact ore-body. The main wall-rock alterations comprise skarnization, actinolitization and phlogopitization. The analytical results of electron microprobe show that the clinopyroxene is diopside-andradite series. The end member of garnet is dominated by andradite and grossular, with minor spessartine and almandine. Fluid inclusion analysis indicate that the temperature of ore-forming fluid decreased significantly (260-360°C to 160 - 280°C) and the salinity of ore-forming fluid keeps constant basically ( 1.74% - 12.51% to 1.74% -11.93% ) from main mineralization stage to post mineralization stage. Hydrogen isotope analysis and oxygen isotope analysis show that the ore-forming fluid is dominated by magmatic water in the early stage, but in late stage, it could be mixed with magmatic and meteoric water. The compositions of sulfur isotope show that sulfur of stratiform-like ore-body was derived from Triassic basalt, yet both of Triassic basalt and Yanshanian granite provide sulfur for contact ore-body. The compositions of lead isotope show that the source of ore-forming material of stratiform-like ore-body is Triassic basalt, yet the source of lead of contact ore-body is Yanshanian granite.

Geology, geochemistry and genesis of Kafang copper deposit in Gejiu, Yunnan Province

Diabase dyke swarms are widespread in the East Tianshan and Beishan regions. LA-ICP-MS zircon U-Pb ages of these diabase vary from 305 Ma to 278 Ma, showing that these dykes were formed during Late Carboniferous-Early Permian magmatism. All diabase samples are subalkali calc-alkali, characterized by slight LREE and LILEs enrichment, and weak negative Ti, Nb and Ta anomalies. The diabase samples have positive e(Nd)(t) values (>+3), high Sr isotopic compositions (initial 87Sr/86Sr values=0.7030–0.7097), and large variation of Pb isotopic compositions, indicating they were derived from a deplete mantle source. Regional geology and geochemistry evidences indicate that these diabase dyke swarms were generated in a lithosphere extensional setting and had the same magma sources. Initial magmas may be a mixture of depleted asthenosphere mantle and enriched lithospheric mantle during rapid magma ascending.

Cheng Yanbo

Papers

Major types and time–space distribution of Mesozoic ore deposits in South China and their geodynamic settings

Spatial-Temporal Distribution of Mesozoic Ore Deposits in South China and Their Metallogenic Settings

Geology, geochemistry and genesis of Kafang copper deposit in Gejiu, Yunnan Province

Geochronology, Geochemistry and Petrogenesis of Diabase Dyke Swarms in East Tianshan, Xinjiang, NW China