大兴安岭松岭地区早白垩世花岗岩地球化学特征及构造意义

Geochemical characteristics and tectonic significance of early Cretaceous granites in Songling area of Greater Khingan Range

对大兴安岭松岭地区早白垩世二长花岗岩、正(碱)长花岗岩进行岩相学和地球化学特征研究,确定其岩石类型、岩石成因及构造环境。地球化学结果显示,岩石具有高硅、高钾、富碱以及贫镁铁钙的特征;富集亲石大离子元素K、Rb,亏损高场强元素P、Ti、Nb;轻稀土元素较富集,重稀土元素相对亏损,具明显的负Eu异常,为铝质A型花岗岩。结合区域资料分析,岩石可能形成于蒙古-鄂霍次克洋闭合后的岩石圈伸展环境之下,岩浆起源于下地壳火成岩物质的部分熔融。

In this paper, the petrographic and geochemical characteristics of the Early Cretaceous monzonitic and(alkaline) syenogranites in the Songling area of Greater Khingan Range were studied to identify their rock types, petrogenesis, and tectonic environments. Geochemical results show that these rocks are aluminum A-type granites of high silicon, high potassium, alkali-rich and magnesium-depleted calcium. They are enriched with lithophile K, Rb, and deplete high field strength elements P, Ti, Nb. Their light rare earth elements are rich while heavy ones are relatively deficient, with a significant negative Eu anomaly. Through analyzing the regional data, it is found that the rocks may be formed under the lithospheric extension environment after the Mongolia-Okhotsk Ocean closed and the magma originated from the partial melting of igneous rocks in the lower crust.