西秦岭糜署岭岩浆带成因及构造意义

糜暑岭岩浆带分布于西秦岭黄渚关EW向深大断裂带中，由2类岩石组成，酸性端元以草关、董河岩体为代表，岩性为中粗粒似斑状石英闪长岩-辉长闪长岩组合；基性端元以挖泉山岩体为代表，岩性为细粒辉长岩，而糜暑岭、黄渚关岩体则是2类岩浆的强烈混合产物，不仅大量的岩石学资料佐证了岩浆混合作用的存在，而且主岩与其混合作用形成的包体具有一致的同位素年龄，主岩中钾长石中的Pb同位素具有明显的幔源性质，因而是一个与幔源岩浆作用有关的构造岩浆带，这为确定区域性构造边界和大地构造单元划分提供了重要证据。同时，也为探讨本区中生代壳幔混合作用和地壳增生提供了新的信息。

THE ORIGINS AND TECTONIC SIGNIFICANCE OF THE MISHULING MAGMA ZONE IN WEST QINLING

The Mishuling magma zone is located in the Huangzhuguan latitudinal deep-fracture zone in west Qinling. It is composed of acid and basic magmas. The main rock is acid magma, which is represented by the Caoguang and Donghe rock bodies and is a medium to coarse grained quartz gabbro diorite. The rock of basic magma, which is represented by the Waquanshan rock body, is a fine-grained gabbro. The Mishuling and Huangzhuguang rock bodies are the result of the strong mixing and mingling of basic magma with acid magma. Petrology data indicates magma mixing. The host rocks and the mafic microgranular enclaves formed by the mixing have similar isotopic ages while the Pb isotopes show the mantle source features in K-feldspar in the host rocks. Therefore the magma zone is related to the mantle magma. This offers firsthand evidence for the determination of the regional tectonic boundary and the differentiation of the geotectonic unit, and also furnishes new information for the study of Mesozoic crust-mantle mixing and crustal accretion in the region.