【摘要】 新疆新源县南部那拉提山北坡出露的石炭纪火山岩主要由玄武岩、玄武质粗面安山岩、粗面安山岩、安山岩、流纹岩和火山碎屑岩组成。该火山岩中玄武岩属于钙碱性系列,安山质岩石和流纹岩属于高钾钙碱性系列,其中轻稀土轻微富集而重稀土相对亏损,玄武岩富集大离子亲石元素、U、Th和Pb,亏损高场强元素。研究表明,该火山岩岩浆可能是由俯冲板片脱水产生的流体交代地幔楔后,地幔楔发生部分熔融的结果。微量元素模拟计算表明,该玄武岩岩浆可以由石榴石二辉橄榄岩经3%～6%的部分熔融得到;安山质岩浆可由玄武岩岩浆经15%～28%的分离结晶形成。更多还原

【Abstract】 The Xinyuan volcanic rocks in western Tianshan mountains mainly consist of basalts, basaltic trachyandesites, trachyandesites, andesites, rhyolites and pyroclastic materials. The basalts constitute calc-alkaline association, whilst the andesitic rocks and rhyolites belong to high-K calc-alkaline series. The REE patterns indicate that LREES are slightly enriched and HREES are comparatively depleted in the studied volcanic rocks. In the primitive mantle-normalized trace element diagrams, basalts show LILE, U, Th and Pb enriched patterns with HFSE troughs. This study displays that the volcanic magma probably came from the partial melting of the mantle wedge, which had undergone metasomatism induced by the subduction fluid. According to calculation, 3 to 6 percent partial melting of garnet-lherzolite could produce the basalt magma. The andesitic magma could be produced by the fractional crystallization of basalt magma, the fraction of which is 15 to 28 percent.更多还原