陕西勉略宁地区赵家坪-苍社一带碳酸岩地质地球化学特征与成因探讨

Geological,Geochemical Characteristics and Origin Discussion of Carbonatite in Zhaojiaping-Cangshe,Mian-Lue-Ning Area

在陕西勉略宁地区赵家坪-苍社一带的中-上元古界碧口群火山岩中发现的碳酸岩具有疑似火成碳酸岩的特征,通过对碳酸岩体的形态、产状以及与围岩接触关系的调查研究,结合镜下鉴定与地球化学研究,证实了本区碳酸岩为岩浆成因碳酸岩;初步认为其为幔源成因,碳酸岩浆可能源于中-晚元古代扬子陆缘裂解作用背景下,地幔富碳酸盐的碱性岩浆上升至相对低压环境、发生碳酸盐-硅酸盐岩浆的不混溶作用。

The type of carbonate intrusions discovered in the mid-upper Proterozoic Bikou group' s volcanic rocks from Zhaojiaping-Cangshe,Mian-Lue-Ning area,Shanxi province,are characterized by features of suspected igneous carbonatite,which has been firstly confirmed based on the geological survey of shapes,occurrences and contact-relations with wall-rocks,combined with microscopic and geochemical studies. It's preliminarily considered that these carbonate intrusions are mantle-derived origin. The carbonate magma that had formed these carbonate intrusions might be originated from the immiscibility of carbonate-silicate magma when the carbonate-rich alkaline magma reached the environment under low pressure from the upper-mantle,under the cracking background of Yangtze continental margin,in mid-latter Proterozoic era.