华南地区中生代Cu (Mo) W Sn矿床成矿作用与洋岭/转换断层俯冲

华南地区是我国重要的金属矿产资源产地，除了发育大量的钨锡钼铋和稀土等金属矿产外，还有铜金矿床分布。本文通过对华南地区29个典型CuMoWSn矿床的时空分布及其与之有关的花岗质岩体的侵位年龄分析，探讨了与不同成矿类型有关的花岗质岩石的地球化学特征。本文认为华南地区10个典型的与Cu有关的矿床主要发生在180~170Ma、160~150Ma以及105~90Ma三个时期，而10个钨矿床主要集中于170~130Ma；4个WSn矿床集中于170~130Ma和120~110Ma；而5个Sn矿床则发育于170~150Ma、130~110Ma以及100~90Ma三个时期。Cu矿床主要与同熔型花岗岩有关，而Mo、WSn既与同熔型花岗岩有关，又与改造型花岗岩有关。在岩石地球化学上，与Cu(Mo)WSn成矿作用有关的花岗质岩石也表现出不同的地球化学特点，如，从Cu(Mo)矿床到WSn矿床SiO2含量有逐渐增大、氧化性逐渐降低、还原性逐渐增加以及分异演化程度有逐渐增高的趋势。与Cu(Mo)Au矿床有关的花岗质岩石具有较低的SiO2（60.3%~68.1%），氧化性较高（Fe2O3/FeO=0.31~1.81），分异演化程度较低（Rb/Sr=0.05~3.3）的特点；与Cu(Pb)(Zn)矿床有关的花岗质岩石具有相对较高的SiO2（73.3%~75.2%），氧化性稍高（Fe2O3/FeO=0.68~1.74），分异程度稍低（Rb/Sr=10.8~57.8）的特点；而与Mo矿床有关的花岗质岩石具有较宽的SiO2（67.3%~76.2%）变化范围，氧化性稍低（Fe2O3/FeO=0.68~1.74），分异演化程度稍低（Rb/Sr=0.6~9.29）；与W矿有关的花岗质岩石的SiO2含量为69.9%~80.1%，还原性稍低（Fe2O3/FeO=0.19~0.76），分异演化程度稍高（Rb/Sr=21.9~61.7）；与WSn矿床有关的SiO2为74.8%~78.7%，还原性较低（Fe2O3/FeO=0.08~0.59），分异程度较高（Rb/Sr=10.8~139）；与Sn矿床有关的花岗质岩石的SiO2为64.8%~76.9%，还原性高（Fe2O3/FeO=0.01~0.58），分异演化程度高（Rb/Sr=1~530）。在结合华南地区花岗岩类岩石的分布特征以及盆岭构造的特点，本文提出华南地区CuMoWSn矿床的成矿作用是不同时期大洋板块或者洋岭多阶段俯冲结果的新成因模型，即早侏罗世休眠的FarallonIzanagi洋岭俯冲导致早—中侏罗世Cu成矿作用；中—晚侏罗世活动的FarallonIzanagi洋岭和转换断层俯冲是中晚侏罗世Cu(Mo)(W)成矿作用以及多阶段WSn成矿作用的触发动力，而白垩纪Izanagi大洋板块俯冲则是白垩纪斑岩型CuWSn成矿作用的诱因。该模型的提出较好地解释了华南中生代大规模岩石圈拆沉—减薄—伸展的机制及其大规模成矿作用的动力。

Mesozoic Cu-Mo-W-Sn Mineralization and Ridge/ Triple Subduction in South China

The paper mainly focuses on the temporal and spatial distributions of 29 typical Cu-Mo-W-Sn deposits in South China, and the ages of related intrusive granitic rocks, and discusses the geochemical features of granitic rocks associated with various metallogenic types, such as SiO2 content, Fe2O3/FeO ratios, and Rb/Sr ratios. This study shows that 10 typical copper deposits in South China occurred mainly at 180~170Ma, 160~150Ma and 105~90Ma., and are associated with syntexis granites (I type), whereas W-Sn are associated with both syntexis (I type) and transformed granite rocks(S type). Copper mineralization occurred at three episodes, namely, 180~170Ma, 160~150Ma and 150~90Ma. Tungsten was mineralized dominantly at 170~130Ma, W-Sn deposit at 170~130Ma and 120~110Ma, and tin deposits at 170~150Ma, 130~110Ma and 100~90Ma, respectively. The granites related to Cu-Mo-W-Sn mineralization show different geochemical characteristics. For example, SiO2 contents increase, oxidation state decrease, redox state increase gradually and higher fractionation occurs from Cu (Mo) deposits to Sn-W deposits. The granites related to Cu-(Mo)(Au) deposits contain less SiO2 (60.3%~68.1%),high oxidization (Fe2O3/FeO=0.31~1.81), less fractionated (Rb/Sr=0.05~3.3) intrusions. In contrast, Cu-(Pb)(Zn) deposits have a high content of SiO2(73.3%~75.2%) and fractionated (Rb/Sr=10.8~57.8) with similar oxidation (Fe2O3/FeO=0.68~1.74) intrusions. Mo-bearing deposits have a wide range of SiO2 (67.3%~76.2%), lowest fractionated (Rb/Sr=0.6~9.29), and low oxidation (Fe2O3/FeO=0.29~0.92) intrusions. The granites related to W deposits are associated with fractionated intrusion (Rb/Sr=21.9~61.7) of intermediate oxidation state (Fe2O3/FeO=0.19~0.76) and higher SiO2 (69.9%~80.1%). However, the W-Sn deposits is related to the intrusion, highly fractionated (Rb/Sr=10.8~139) and low reduced (Fe2O3/FeO=0.08~0.59), with SiO2 content from 74.8% to 78.7%; whereas the granitic rocks hosting Sn mineralization have a wide range of SiO2 (64.8%~76.9%), are highly fractionated (Rb/Sr=1~530) and reduced (Fe2O3/FeO=0.01~0.58). Combined with distribution of granitic rocks and characteristics of basinal ridges in South China, this study proposed that the Cu-Mo-W-Sn mineralization in South China was the result of oceanic plates in several stages and/or multi-stage ridge subduction, i.e., Early Jurassic Farallon Izanagi active ridge subduction responsible for the Early Jurassic Cu mineralizations, middle Later Jurassic Farallon Izanagi triple ridge subduction and transfaults subduction resulting in the Middle Jurassic Cu(Mo)(W) mineralizations and subsequently large scales W-Sn mineralizations in several episodes, the Cretaceous Izanagi plate subduction beneath the South China craton is the source of Cretaceous porphyry Cu, W and Sn mineralizations.