豫西雷门沟钼矿区西段隐爆角砾岩地球化学特征及地质意义

东秦岭雷门沟钼矿是近年来在豫西新探获的一处超大型钼矿床,同时在隐爆角砾岩中发现了钼矿体。为查明隐爆角砾岩与成矿作用的关系,本文对矿区内隐爆角砾岩中角砾和胶结物进行了岩相学、地球化学的分析和研究。主量元素表明角砾属于过铝质高钾钙碱性-碱性岩石系列,而胶结物属于弱过铝质高钾拉斑系列。角砾和胶结物的稀土元素含量∑REE变化较大,均显示不同程度的轻稀土元素富集和负铕异常,微量元素蛛网图显示胶结物呈富集大离子亲石元素(Cs、Rb、Ba、K和Pb),相对亏损高场强元素(Ta、Nb、Ti),与新太古界太华群片麻岩、花岗斑岩特征类似。综合东秦岭年代学资料和区域构造演化背景,雷门沟隐爆角砾岩可能形成于造山后伸展体制,其隐爆作用伴随着钼成矿过程。

Geochemical characteristics of cryptoexplosive breccias in the western part of Leimengou Mo deposit in western Henan and their geological significance

Leimengou Mo deposit is a super large deposit recently discovered in the western Henan Province, and Mo ore was present mainly in the cryptoexplosive breccia. In order to find out the genesis of the cryptoexplosive breccia and its relationship to metallogenesis, the major elements, trace elements, and rare earth elements of the breccias and cements in the cryptoexplosive breccia was analyzed. The values of major elements of the breccias show the peraluminous high potash calc-alkaline and alkaline series and of cements weak peraluminous high potassium tholeitic series. The total values of rare earth elements of the breccias and cements varied relatively widely, both showing enriched LREE and obviously negative Eu anomaly in different degrees. The spider diagram of trace elements shows the cements exhibits the enriched characteristics of LILE (Cs, Rb, Ba, K, Pb), and relatively depleted HFSE (Ta, Nb, Ti), similar to Archaean gneiss of the Taihua Group and the granite porphyry. Combined with the geochronological data of the East Qinling and the regional tectonic evolution, it was inferred that the Leimengou cryptoexplosive breccia was possibly formed in the post-orogenic extensional setting, and the cryptoexplosive process was accompanied by the molybdenum mineralization.