湖北襄阳地区龙潭组富锂黏土岩地球化学特征及其对物源和古沉积环境的指示

Geochemical Characteristics,Provenance and Palaeosedimentary Environment of Lithium-rich Claystone in Longtan Formation in Xiangyang Area,Hubei Province

湖北襄阳地区二叠系龙潭组底部发育一套富锂黏土岩,其形成的古环境条件对黏土型锂矿找矿勘查具有重要指示作用。采集大坪矿区的龙潭组黏土岩样品,通过主量、微量和稀土元素分析,恢复黏土岩的古沉积环境和物源。结果表明,大坪矿区龙潭组黏土岩SiO_(2)含量为22.38%~41.08%,Al_(2)O_(3)含量为19.36%~34.80%,TFe_(2)O_(3)含量为1.36%~25.62%,整体呈现富硅、富铝、富铁的特征;Li_(2)O含量与累托石(r=0.738)、Cu(r=0.594)、Zn(r=0.724)具有较强的正相关性;Sr/Ba比值主要为2.62~14.00,指示古盐度为海相咸水;V/Cr比值为0.535~1.84,V/(V+Ni)比值为0.77~0.99,δCe为1.04~1.67,说明其沉积时属于还原环境;Sr/Cu比值为4.14~11.27,CIA值为76.20~88.11,指示古气候趋向于温暖或炎热的潮湿环境,物源区风化强烈。结合区域地质演化史,推断物源可能为勉略缝合带和南秦岭构造带中形成的与俯冲有关的岩浆岩,以及淮阳古陆出露的碳酸盐岩。在襄阳地区可以充分利用前人累托石黏土矿勘查成果,推进龙潭组黏土型锂矿的找矿勘查工作。

A set of lithium-rich claystone is developed at the bottom of the Longtan Formation of Permian in Xiangyang area,Hubei Province.The paleosedimentary conditions of its formation have an important indication for the prospecting and exploration of clay-type lithium deposits.The claystone samples of Longtan Formation in Daping mining area were collected,and the paleosedimentary environment and provenance of claystone were discussed through the analysis of major,trace and rare earth elements.The results show that the content of SiO_(2)is_(2)2.38%to 41.08%,Al_(2)O_(3)is 19.36%to 34.80%,and TFe_(2)O_(3)is 1.36%to_(2)5.62%in Longtan Formation claystone in Daping mining area,which is rich in silicon,aluminum and iron.Li_(2)O content has a strong positive correlation with rectorite(r=0.738),Cu(r=0.594)and Zn(r=0.724).The Sr/Ba ratio is mainly_(2).62 to 14.00,indicating that the paleosalinity is marine salt water.The V/Cr ratio is 0.535 to 1.84,the V/(V+Ni)ratio is 0.77 to 0.99,and theδCe is 1.04 to 1.67,indicating that it was deposited in a reducing environment.The Sr/Cu ratio is 4.14 to 11.27,and the CIA value is 76.20 to 88.11,indicating that the paleoclimate tends to be warm or hot humid environment,and the provenance area is strongly weathered.Combined with the regional geological evolution history,it is inferred that the provenance may be the subduction-related magmatic rocks formed in the Mianlue suture zone and the South Qinling tectonic belt,as well as the carbonate rocks exposed in the Huaiyang ancient continent.In Xiangyang area,the previous exploration results of rectorite clay deposits can be fully utilized to promote the prospecting and exploration of clay-type lithium deposits in Longtan Formation.