【摘要】 分布于哀牢山-红河断裂带西南侧的金平上二叠统玄武岩属于低钛拉斑玄武岩（LT）（Ti/Y<500）。其地球化学特征总体与洋岛玄武岩（OIB）相似。根据其岩相学、主量元素、微量元素特征,将其划分为LT1和LT2两个地球化学亚类型。它们的分布和主要地球化学标志为:LT1分布于下部,高Mg^#（48～63）,SiO₂（50％～56％）,高∑REE（118～145μg/g）、低Fe₂O₃（1.36％～1.63％）,Na₂O（1.88％～3.17％）,TiO₂（1.37％～1.92％）,高Th、U,低Nb、Ta和Sr负异常;LT2分布于上部,低SiO₂（47％～56％）,Mg^#（34～59）,低∑REE（75～117μg/g）,高Fe₂O₃（1.56％～2.47％）、Na₂O（2.33％～5.03％）、TiO₂（1.49％～2.34％）,Sr强负异常。二者地球化学特征的差异是同一母岩浆经不同的分离结晶和同化混染作用的结果。金平与宾川峨眉山的化学地层学对比表明,金平LT1和LT2玄武岩与宾川峨眉山玄武岩下部的LT1、LT2十分相似,它们可能是同时,或在类似的环境下形成的。金平玄武岩属于峨眉山大火山岩省的一部分,同为峨眉地幔柱早期活动的产物。新生代哀牢山-红河断裂的左滑剪切运动导致了宾川与金平玄武岩的错位。更多还原

【Abstract】 The late Permian flood basalts at Jinping area, located to the SW of Ailaoshan-Red River fault in SW Yunnan province, are characterized by low-Ti tholeiite, which has low TiO2 contents (<2. 5%) and low Ti/Y ratios (<500). Their geochemical characteristics are similar to those of the oceanic island basalt (OIB). Based on their petrography, major elements and trace elements data, they are further sub-divided into two geochemical types, i. e. LTl and LT2 basalts. The LTl basalts at the lower part exhibit high Mg# (49 - 63), SiO2 (47% - 53%), Th, U and ΣREE(118-145μg/g), and low Fe2O3(l. 36%- 1.63%), Na2O(1.88%-3. 17%), TiO2(l. 37% - 1. 92%) and Nb, Ta, and negative Sr anomalous. The LT2 basalts at the upper part exhibit relatively lower Mg# (30 - 59), ΣREE(72 - 117μg/g), higher Fe2O3(l. 56% - 2. 47%), Na2O(2. 33%- 5. 03%), TiO2(1.49% - 2. 34%), and strong Sr negative anomaly. Element data suggest that chemical variations of the LTl and LT2 lavas are evolved from a common parental magma by different degree of crystallization and crustal contamination. The lavas might be generated from a shallow volatile metasomatism mantle with high-degree of partial melting, and then experienced garnet + clinopyroxene fractional crystallization and crustal contamination. The LTl lavas had obtained more significant crustal component (contamination) than the LT2 lavas. Comparing their geochemical stratigraphy with that of the Emeishan basalts in the Binchuan area, these features are similar to the LTl and LT2 basalts of Binchuan area respectively, which were generated from a shallow volatile metasomatism mantle at the early active stage of the Emeishan mantle plume. These basalts are the products of Emei mantle plume and are a part of Emeishan flood basalts. The sinistral movement of the Ailaoshan-Red River shear zone resulted in the displacement of Jinping and Binchuan basalts.更多还原