陕西商南松树沟橄榄岩体的成因及侵位机制

Petrogenesis and Emplacement of the SongshugouPeridotite in Shagnan, Shaanxi

陕西商南县松树沟橄榄岩体是秦岭造山带中具重要意义和争议较大的岩体。本文通过岩体的结构、构造变形及相应的变质作用研究，提出了该橄榄岩体是由超基性岩浆在壳幔过渡带结晶而成，并经历了与围岩一致的麻粒岩相（≥８００℃）条件下的早期塑性变形以及角闪岩相和绿片岩相退化变质条件下与逆冲上升有关的韧性剪切变形。从而证明了松树沟橄榄岩体并不是上地幔岩石的残片，而是由岩浆在深部地壳环境下结晶而成并以固态构造侵位于地壳的上部。岩体的上升过程与晋宁期华北克拉通向南仰冲有密切关系。

The Songsugou peridotite in Shangnan, Shaanxi Province is an important but petrogenetically debated ultramafic massif in the Qinling orogenic belt. Based on the studies of petrotexture, structural deformation and the relevant metamorphism, this paper indicates that this peridotite massif is the product of ultramafic magma cumulated at the crustmantle transtion zone and has undergone the early stage of plastic deformation under the condition of granulite facies(≥800℃)and late ductile shearing at amphibolite and greenschist facies in relevance to uplifting. These studies , therefore, suggest that the Songsugou peridotite is not a tectonic massif of the upper mantle but a ultramafic magmatic rock body crystallized in deep crust and tectonically emplaced in the upper crust. The process of the uplifting is intimatedly associated with the south ward obduction of the North China Craton in Jinning movement.