Geochemical study of Cretaceous magmatic rocks in Chuzhou region, Low Yangtze River Metallogenic Belt:Implications for petrogenesis and Cu-Au mineralization
Geochemical study of Cretaceous magmatic rocks in Chuzhou region, Low Yangtze River Metallogenic Belt:Implications for petrogenesis and Cu-Au mineralization
复制标题
长江下游成矿带滁州地区白垩纪岩浆岩地球化学研究:对岩石成因及铜金成矿的启示
DOI：
10.1080/00206814.2017.1373606
复制
发表时间：
2017
影响因子：
2.6
通讯作者：
Lee IS
中科院分区：
文献类型：
--
作者：
Hu ZL;Yang XY;Lee IS
长江下成矿带是中国最重要的多金属矿床带之一。LYRMB中的楚县、马厂和上姚铺侵入岩为中间岩系，主要由二长岩和石英二长岩组成。本研究分析了大块岩石主微量元素、锆石U-Pb定年和Hf同位素。得到了5个年龄，分别为(1)楚县121.8±1.9和124.0±1.4 Ma,(2)马场侵入123.1±2.0 Ma,(3)上姚铺126.6±1.8和123.4±1.9 Ma，表明区域火成岩活动发生在早白垩世，与东部燕山期大规模岩浆活动相一致。这3块侵入岩均为高mg埃达克岩，大部分具有高Si、高Na、低Sr的地球化学特征，可解释为洋壳俯冲部分熔融作用。高mg#特征表明岩浆与地幔发生反应。这些埃达克岩的负锆石ε值表明，岩浆同化了古地壳物质，如太古宙大陆地壳，南郯城-庐江断裂基底。黑云母钛温度结果（约700℃）表明侵入岩浆温度较低。约1.25 ~ 1.8亿年间，太平洋板块向西南向LYRMB方向俯冲，可以解释该区的岩石成因和区域铜金成矿机制。俯冲洋壳部分熔融形成的岩浆具有系统高的Cu-Au含量，有利于相应的成矿作用。
The low Yangtze River metallogenic belt (LYRMB) is one of the most important poly-metal deposit belts in China. The Chuxian, Machang and Shangyaopu intrusions in the LYRMB are intermediate rock series, mainly composed of monzonite and quartz monzonite. In this study, bulk rock major and trace elements, zircon U–Pb dating and Hf isotope were analysed. Five ages have been obtained as (1) Chuxian, 121.8 ± 1.9 and 124.0 ± 1.4 Ma, respectively, (2) Machang intrusion, 123.1 ± 2.0 Ma and (3) Shangyaopu, 126.6 ± 1.8 and 123.4 ± 1.9 Ma, indicating that the regional igneous activity was in Early Cretaceous, being consistent with the massive Yanshanian magmatic events in eastern China. These three intrusions are identified as a high-Mg adakite, most of them showing geochemical features of high Si, high Na and low Sr, which can be interpreted as partial melting of subducted oceanic crust. High Mg# characteristics indicate the magmas reacted with the mantle. The negative zirconεHfvalues of these adakites suggest that the magmas have assimilation of old crustal material, e.g. Archaean continental crust, the basement of the south Tancheng–Lujiang (Tan–Lu) fault. Biotite Ti temperature result (about 700°C) shows that intrusive magma has a relatively low temperature. Petrogenesis and regional Cu–Au mineralization mechanism may be explained by Pacific plate subduction during about 125–180 million years subducted to southwest towards the LYRMB. Magmas formed by partial melting of subducted oceanic crust have systemically high Cu–Au contents, which are conducive to corresponding mineralization.