铜陵舒家店矿床年代学-地球化学特征及其意义

本文对铜陵舒家店辉石闪长岩开展了年代学和地球化学的系统研究。结果表明,舒家店辉石闪长岩的侵入年龄为140.5±1.4Ma,低于铜陵地区花岗闪长岩年龄。辉石闪长岩是矿床赋矿岩石,据此推测成矿时代也应该同为140.5Ma左右,或稍晚于岩浆岩侵位的时代。舒家店辉石闪长岩的地球化学特征表明其SiO2含量为50%左右,属于稍偏基性的岩类,并且具有大离子亲石元素(LILE:Ba,Sr,Th,Pb)的富集,而相对亏损高场强元素(HFSE:Zr,Nb,Hf),反映出该侵入岩的原始岩浆可能来源于受到了板片俯冲作用改造的富集地幔。舒家店岩体及铜金矿床形成的大地构造背景可能与古太平洋板块俯冲密切相关,位于大陆边缘岩浆弧的内陆一侧环境,它可能是俯冲洋壳部分熔融形成的熔体或流体交代地幔楔并使地幔楔发生部分熔融而形成的玄武质岩浆侵位到地壳浅部过程中混染了大量地壳物质而成。

Chronological-Geochemical characteristics and its significance of the Shujiadian intrusion, Tongling orefield

The Tongling region of Anhui Province is an important ore district in the famous Lower and Middle Yangtze River Cu-Au-Fe-S metallogenic belt in eastern China. It is also a good example of skarn deposits in the world. Recently, a porphyry Cu-Au deposit associated with pyroxene diorite was discovered in the Shujiadian region. Given that this is the first porphyry deposits found in Tongling ore district, detailed petrological and geochemical work may have significant implications for future exploration. Here we report chronology and element geochemistry studies on Shujiadian pyroxene diorite. The LA-ICP-MS zircon U-Pb dating result reveal the pyroxene diorite from Shujiadian region is 140.5±1.4Ma, which is younger than the granodiorite in Tongling. And the metallogenetic epoch of the Shujiadian pyroxene diorite maybe slightly younger than 140.5Ma. Our results show that the tectonic setting of the Shujiadian pyroxene diorite should be closely related to the paleo-Pacific plate subduction of the continental margin. It may form during the ascend and emplacement processes of magma which is derived from mantle wedge partial melting by subducted oceanic slab fluids metasomatism, during which the mantle source magma might have been transformed with crustal contamination.