新疆老山口金矿岩浆隐爆角砾岩地质地球化学

新疆东准噶尔老山口金矿区发育有与金矿化密切有关的次火山闪长玢岩及与之密切伴生的闪长玢岩质隐爆角砾岩和闪斜煌斑岩质隐爆角砾岩 ,它们是在陆相火山作用下由同源岩浆分异演化而形成的产物。角砾岩具有浅成—超浅成环境及热塑、高压释放状态下的成岩特征。角砾岩的角砾、胶结物和次火山岩三者的岩石类型、岩相学特征和地球化学特征基本一致 ,具有稀土总量较低 ,轻稀土相对富集 ,重稀土相对亏损 ,铕异常不明显 ,大离子亲石元素相对富集 ,高场强元素相对亏损等特征。结合其构造背景、地质产状、岩石学和地球化学特征分析 ,这套岩石来源于受俯冲洋壳释放富含大离子亲石元素或强不相容元素流体交代过的亏损地幔楔。

GEOLOGY AND GEOCHEMISTRY OF MAGMATIC CRYPTOEXPLOSION BRECCIA IN LAOSHANKOU GOLD DEPOSIT, XINJIANG

In the Laoshankou gold deposit, eastern Junggar, Xinjiang, there occurred diorite-porphyrite cryptoexplosion breccia, spessartite cryptoexplosion breccia and associated subvolcanic diorite-porphyrite. They were differentiated and evolved from co-magma, and are closely associated with gold mineralization. Diagenetic characteristics of these magmatic cryptoexplosion breccia show they were formed in hypabyssal-shallow-hypabyssal or subvolcanic environment and in thermoplasticity and high pressure. Their rubbles and cements as well as the subvolcanic diorite-porphyrite are alike or similar in petrography and geochemistry. They are relatively poor in total rare-earth elements (REE), rich in light-REE and large ion lithophile elements (LILE) and depleted in heavy-REE and high field strength elements (HFSE), with no Eu-anomaly. Based on the analysis of tectonic setting and geological, petrological and geochemical characteristics, it is concluded that the set of magmatic cryptoexplosion breccia and subvolcanic rock may be derived from depleted mantle wedge which was metasomatized by certain fluid rich in large ion lithophile elements or highly incompatible elements.