河南石瑶沟钼矿床花岗岩成因及构造背景

石瑶沟钼矿床位于河南省栾川县境内,是近年来探明的大型钼矿床,大地构造位置处于华北地台南缘与东秦岭褶皱带的衔接部位。通过对比石瑶沟矿区花岗斑岩锆石U-Pb定年结果及辉钼矿Re-Os同位素定年结果及花岗斑岩矿化蚀变特征研究,认为该区钼矿化与早白垩世岩浆活动具有密切的时空关系。花岗斑岩具有富硅、铝,富碱,低钙、镁的特点;稀土元素中轻稀土富集,δEu具轻度亏损;微量元素中强烈富集Rb、Th、U,轻度亏损Sr。主、微量及稀土元素地球化学特征总体显示该岩体属于钾玄岩系列、过(准)铝质S型花岗岩。结合区域地质背景、岩石学及地球化学特征,认为该岩体是在板块碰撞后造山带垮塌、伸展构造环境下,由上地壳变质砂屑岩受地幔岩浆底侵加热、同化混染及源区白云母的脱水作用而发生部分熔融形成的。

Genesis and tectonic background of granite intrusion related with Shiyaogou molybdenum polymetallic mineralization, Henan

The large-sized Shiyaogou Mo deposit is located in the Luanchuan county, Henan Province, which was found and explored in recent years. Tectonically the deposit occurs at the convergence area between the southern margin of North China Craton and Qinling fold belt. By comparing isotope dating results of Zircon U-Pb from Early Cretaceous granite porphyry and the Re-Os isotope from molybdenite as well as mineralization and alteration characteristics of granite porphyry, it is thought that the Mo polymetallic mineralization had close temporal-spatial relationship with Early Cretaceous magma activities. The granite porphyry was rich in silicon, aluminum, alkalis and poor in calcium, magnesium and showed enrichment of LREE, and mild europium depletion. Also Rb, Th, U enrichment, and mild Sr depletion. The geochemical characteristics of major, trace and rare earth elements suggested that the granite porphyry belongs to shoshonite series and per-aluminous (quasi-aluminum) S-type granite. In combination with regional geological background and petrological, geochemical characteristics, the granite porphyry was possibly formed by melt partially of upper crust metamorphic psammite under heating of underlying magmatic mantle, assimilating hybridism and dehydration process of muscovite from source area under the tectonic setting of collapsing, stretching tectonic setting after the plate collision.