西南天山哈拉达拉岩体的锆石SHRIMP年代学及地球化学研究  

Zircon SHRIMP chronology and geochemistry of the Haladala gabbro in south- western Tianshan Mountains

作　　者：薛云兴[1] 朱永峰[1] 

机构地区：[1]造山带与地壳演化教育部重点实验室,北京大学地球与空间科学学院,北京100087

出　　处：《岩石学报》2009年第6期1353-1363,共11页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40572033);国家科技支撑计划重点项目(2006BAB07BO8)资助成果.

摘　　要：西南天山哈拉达拉侵入体由橄长宕、橄榄辉长岩和辉长岩组成,橄长岩和橄榄辉长岩具有典型的堆晶结构,堆晶矿物以斜长石和橄榄石为主。辉石、角闪石和金云母主要为堆晶间隙矿物。辉长岩发育辉长—辉绿结构。结晶分异作用在岩浆演化过程中起重要作用。对从辉长岩中分选出来的锆石进行的SHRIMP年代学研究表明,辉长岩形成于308.3±1.8Ma(MSWD=0.86,n=15)。哈拉达拉岩体稀土元素配分模式与E-MORB相似,具有高Rb、Cs、Ba及Sr的特点,^(87)Sr/^(86)Sr初始比值0.7040～0.7050.这些特征表明,岩浆源区具有富集地慢的特征(古南天山洋俯冲流体交代形成了富集地幔)。根据平坦的稀土元素配分模式以及Gd、Sm、Nb、Zr等微量元素的地球化学行为判别,岩浆源区岩石为含角闪石的尖晶石二辉橄榄岩。批式熔融模拟计算显示,地幔岩10%～15%的部分熔融能够形成哈拉达拉岩体的母岩浆。母岩浆通过48%～50%的结晶分异作用则能够形成哈拉达拉岩体。早期结晶的橄榄石和斜长石通过堆晶作用形成橄长岩和橄榄辉长岩,剩余岩浆结晶形成辉长岩。The Haladala basic-ultrabasic pluton in southwest Tiansban Mountains consists of troctolite, olivine gabbro and gabbro. Typical cumulate textures; occur in the troctolite and olivine gabbro. The cumulate minerals tire mainly of olivine and plagioclase. The inter-cumulate minerals are mainly of pyroxene, amphibole mid phlogopite. Gabbro shows typical gabbro-ophitic textures. Fractional crystallization played an important role ill the formation of the Haladala intrusion. The zircon SHRIMP dating indicates that the gabbro crystallized at Late Carboniferous (308. 3 +/- 1. 8Ma, MSWD =0. 86, n = 15). The REE distribution pattern, of the Haladala rocks are Similar to that of the E-MORB. The studied samples With initial (87)Sr/(86)Sr of 0. 7040 -0. 7050 contain relatively abundant Rb, Cs, Ba and Sr. All these data suggest that the source Of the Haladala magma Was ail enriched mantle. Based oil their flat REE distribution patterns and geochemistry of other trace elements, We suggest that the rocks of mantle source. are amphibole-bearing spinel Iherzolite. The metasomatism caused by the subduction fluid of the Paleo- south Tianshan Ocean led to the formation of file enriched mantle. According to calculation, the primary magma of the Haladala pluton was formed by 10% similar to 15% partial melting of amphibole-bearing spinel Iherzolite.

关 键 词：西南天山 橄长岩 辉长岩 地球化学 哈拉达拉 新疆 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]