川西拗陷中段蓬莱镇组物源的地球化学示踪

探讨川西拗陷中段上侏罗统蓬莱镇组物源问题。采用地球化学示踪方法,通过岩石薄片、痕量元素和稀土元素等综合分析,结合前人的研究成果,对蓬莱镇组源区背景属性和物源特征进行研究。结果表明:研究区蓬莱镇组砂岩碎屑组分以石英为主,其次是长石及各种岩屑;REE配分模式与大陆上地壳稀土元素配分模式基本一致,轻稀土元素富集,Eu负异常较为明显。其源区的构造环境是从海相过渡到陆相,最后演化成复杂的源区。川西拗陷中段蓬莱镇组有龙门山、大巴山-米仓山多个物源区,北部的主要物源区为大巴山-米仓山,南部的物源区为龙门山,中部则为混源区。

Provenance of depositional sources of the Penglaizhen Formation in west Sichuan depression:Evidence from geochemistry

Geochemical tracer method,combined with the study of rock thin sections,trace elements and rare earth elements analysis,previous research results,et.al.,is used to investigate provenance of Upper Jurassic Penglaizhen Formation in west Sichuan depression.It shows that the detrital components of sandstone are composed of mainly quartz,the rest are feldspar and other clasts. Geochemical analysis shows that the REE distribution pattern in the study area is basically similar with those in the earth’ s continental crust.Light rare earth elements are enriched,and Eu negative anomaly is obvious. The structural setting of provenance transits from marine environment to continental sedimentary environment and to complicated provenance.It reveals that the provenance of Penglaizhen Formation sandstone in west Sichuan depression is from the Longmen Mountains,Daba Mountains-Micang Mountains.The provenance of Penglaizhen Formation in the middle north area of west Sichuan depression is mainly from Daba Mountains-Micang Mountains region, and the provenance of Penglaizhen Formation in the south of west Sichuan depression is from Longmen Mountains,while the provenance of Penglaizhen Formation in the central region is of mixed sources area.