贵州白层超基性岩对右江盆地燕山晚期拉张环境深源岩浆演化作用的启示——来自地球化学的证据

发布时间：2018-03-23 11:08

本文选题：扬子地台　切入点：超基性岩　出处：《地质通报》2017年Z1期

【摘要】：白层超基性岩产出于扬子地台西南缘,该区域存在多期次的岩浆活动,出露多处超基性岩体。对白层11件超基性岩样品进行了主量和微量元素(包括稀土元素)及铂族元素分析,结果表明,白层超基性岩主量元素变化范围不大,具低钠富钾钙碱性岩石的地球化学特征;该超基性岩富集Ba、Sr、Rb等大离子亲石元素及Nb等高场强元素;稀土元素总量高,球粒陨石标准化曲线呈强烈的右倾趋势,轻、重稀土元素分馏明显,Eu、Ce异常不明显;铂族元素总含量低,且分异不明显。该超基性岩的地球化学特征显示,其形成于燕山晚期右江盆地大规模岩石圈伸展减薄的构造背景下;岩浆来源于低程度部分熔融的超镁铁质地幔,石榴子石及硫化物在熔融过程中残留于源区。岩浆在上升过程中未发生明显的地壳物质混染。岩浆结晶分异程度不高,发生了橄榄石与单斜辉石的结晶分异但未发生斜长石的分离。
[Abstract]:The ultrabasic rocks occurred in the southwestern margin of the Yangtze platform, and there were many magmatic activities in this area. The principal and trace elements (including rare earth elements) and platinum group elements of 11 ultrabasic rock samples in the white layer are analyzed. The results show that the main elements of the ultrabasic rocks in the white bed have little change. The ultrabasic rocks are rich in large ion lithophile elements, such as Ba-Sr-Rb and NB, and have high rare earth elements, and the standardized curve of chondrites shows a strong right-dip trend, which is light, and it is characterized by the geochemical characteristics of low-sodium and K-rich calc-alkaline rocks, the ultrabasic rocks are enriched in large ion lithophile elements, such as Ba-Sr-Rb and NB and so on. The fractionation of heavy rare earth elements is not obvious, the total content of platinum group elements is low, and the differentiation is not obvious. The geochemical characteristics of the ultrabasic rock show that it was formed in the tectonic setting of large-scale lithospheric extension and thinning in the late Yanshanian basin. The magma originated from the low-degree partial melting ultramafic mantle, and the pomegranate and sulfides remained in the source region during the melting process. There was no obvious crustal material mixing during the magma rising, and the degree of crystallization differentiation of the magma was not high. The crystal differentiation of olivine and clinopyroxene occurs but no separation of plagioclase occurs.
【作者单位】：中国地质大学地球科学与资源学院;中国地质调查局成都地质调查中心;
【基金】：中国地质调查局项目《贵州贞丰金-铀多金属成矿区控矿因素与找矿方法研究》(编号:12120113094400)
【分类号】：P588.125;P588.115

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