长江中下游铜陵地区宝山岩体地球化学研究

发布时间：2018-06-02 02:15

本文选题：埃达克岩 + 岩浆混合　；参考：《地球化学》2017年05期

【摘要】：长江中下游地区与铜金矿床有关的埃达克岩成因仍然存在分歧。对铜陵宝山地区的侵入岩和其中的包体进行了系统的矿物学、岩石学和元素地球化学研究。结果表明:(1)宝山岩体岩性变化较大,从辉石闪长岩到花岗闪长岩均有;(2)暗色基性岩常常被淡色酸性的花岗闪长岩所包裹,部分界限呈过渡状态;(3)LA-ICPMS锆石U-Pb定年结果表明,宝山花岗闪长岩和其中的辉石闪长岩包体分别形成于(143.8±3.2)Ma(2σ,MSWD=2.3)和(142.9±2.9)Ma(2σ,MSWD=2.2),属于早白垩世;(4)宝山岩体地球化学特征表明其主体具有典型的埃达克岩特征,如较大SiO_2含量变化范围(52.88%~63.66%),高Al_2O_3含量(平均值为16.03%)、高Sr/Y(33.4~102,平均为72.9)和Sr/La比值,低Y和Yb含量、低(La/Yb)N(14.6~26.6,平均值为21.4)和K_2O/Na_2O(平均值为0.39)比值。(5)野外岩石接触关系和岩石地球化学特征表明,宝山埃达克质岩可能为岩浆混合成因,混合的两个端元分别为高硅和低硅端元。高硅端元为俯冲洋壳熔融形成的熔体并发生不同程度磁铁矿的结晶分异,而低硅端元为高Ni、Cr、V、Co的岩石圈地幔熔体。铜陵宝山岩体的地质与地球化学研究结果表明,铜陵地区中生代埃达克质岩和大规模铜金成矿作用可能形成于俯冲背景之下。
[Abstract]:In the middle and lower reaches of the Yangtze River, there are still differences in the genesis of the adakite associated with the copper and gold deposits. The mineralogy, petrology and element geochemistry of intrusive rocks and inclusions in Baoshan area of Tongling are studied systematically. The results show that there is a great variation in lithology of Baoshan rock mass, from pyroxene diorite to granodiorite, the dark basic rocks are often surrounded by light-colored acidic granodiorite, and some of the boundaries are in a transitional state. The U-Pb dating results of zircon show that: 1. The geochemical characteristics of Baoshan granodiorite and its pyroxene diorite xenoliths formed in 143.8 卤3.2)Ma(2 蟽 MSWD2. 3) and 142.9 卤2.9)Ma(2 蟽 m MSWD2. 2, belonging to the early Cretaceous, indicate that the main body is characterized by typical adakite features. If the range of variation of SiO_2 content is 52.88 and 63.66, the content of Al_2O_3 is high (the average is 16.03, the average value is 16.03, the average is 72.9) and the ratio of Sr/La, the contents of Y and Yb are low, the contents of Y and Yb are 14.626.6, the average is 21.4) and the ratio of K _ 2O / na _ 2O (average is 0.39). Baoshan adakitic rocks may be of magmatic mixing origin, and the mixed two terminal elements are high silicon and low silicon end elements respectively. The high silicon end element is the melt formed by subduction oceanic crust melting and the crystallization differentiation of magnetite occurs to different degrees, while the low silicon terminal element is the lithospheric mantle melt with high NiCrCrVPco content. The geological and geochemical results of Tongling Baoshan rock body indicate that the Mesozoic adakitic rocks and large-scale copper-gold mineralization may have been formed in the subduction setting in Tongling area.
【作者单位】：合肥工业大学资源与环境工程学院;合肥工业大学矿床成因与勘查技术研究中心;中国科学技术大学;中国地质大学(北京);
【基金】：国家自然科学基金(41373035,41203028) 合肥工业大学中央高校基本科研业务费专项资金(112-4115102017)
【分类号】：P584;P618.41;P618.51

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