阳泉矿区泥岩地球化学特征及地质意义

Geochemical features of mudstone and geological significance in Yangquan Mining Area

为研究阳泉矿区太原组、山西组的沉积环境、物源及源区构造背景,对该区泥岩微量及稀土元素进行分析,结果表明:该区亲石元素较为富集,高场强元素Ti、Zr、Hf、Th丰度高于上地壳,Rb、Sr、Nb、Ta等元素有所亏损;稀土元素总量较高,轻重稀土元素比值及(La/Yb)N比值显示轻、重稀土分异明显,表现为轻稀土富集、重稀土相对亏损、Eu明显负异常、Ce微弱负异常的分布模式。对Sr/Cu、V/(V﹢Ni)、Sr/Ba、δCe和Ceanom等特征参数的分析,显示该矿区泥岩属于过渡相-陆相沉积,处于还原、厌氧、半咸水沉积环境。据泥岩微量、稀土元素组合及其判别图解,该矿区源岩以长英质岩石为主,与太原组相比,山西组物源明显受花岗岩的影响,物源区构造背景为大陆岛弧和活动大陆边缘。

In order to study a sedimentary environment of Taiyuan Formation and Shanxi Formation in Yangquan Mining Area,provenanceand source region structure background,an analysis was conducted on the trace element and rare earth element of the mudstone in the are-a. The results showed that the lithophile elements in the area were quite enrichment,the Ti,Zr,Hf and Th abundances of the high fieldstrength elements were higher than the upper crust and the Rb,Sr,Nb,Ta and other element were loss in some case. The rare earth elementtotal was high,the ratio of light and heavy rare earth elements and(La/ Yb)Nratio showed that the difference of the light and heavy rareearth was obvious and that the light rare earth was enrichment and heavy rare earth was loss relatively. Eu was obvious negative anomalyand Ce was in a weak negative anomaly distribution mode. The analysis on Sr/ Cu,V/(V ﹢ Ni),Sr/ Ba,δCe,Ceanomand other feature pa-rameters showed that the mudstone in the study area was a transition phase-continental facies sedimentation and in a reduction,anaerobicand brackish water sedimentary environment. Based on the combination of the mudstone trace elements and rare earth element and the dis-criminant illustrations,the source rocks in the study area were felsic rocks mainly. In comparison with Taiyuan Formation,the provenance ofShanxi Formation was obviously affected by the granite. The structure background of the provenance area could possibly be the island arc ofthe mainland and the edge of the active mainland.