摘要
主要从岩石学、矿物学、岩石分类、C、O、Sr同位素、碳酸岩与矿化的关系等各方面对 (碱性 )碳酸岩的研究进行了较为全面的总结 ,并结合近 2 0年来实验岩石学、流体包裹体研究、CO2 H2 O NaCl流体体系的性质的研究 ,对碳酸岩岩浆的来源及成因、岩浆—热液的演化进行了分析和探讨。碳酸岩形成至少经历了三个阶段 ,即岩浆阶段、岩浆期后阶段 (气相碳酸岩 /岩浆热液阶段 )、交代碳酸岩阶段。而作为与碳酸岩在空间和成因上有密切联系的基性、超基性岩、碱性岩杂岩体 ,则经历了碳酸岩成岩阶段以前的岩浆不混熔作用、结晶分异作用、岩浆结晶作用以及碳酸岩形成之后的围岩蚀变 (霓长岩化 )
On the basis of mineralogy, petrology, carbon, oxygen and strontium isotopes and the relationship between carbonatite and mineralizations, the originand features of carbonatite is summarized. The carbonatites mainly occurred in the rift zones of cratons and within plates. They are often associated with mafic, ultramafic and alkaline rocks as a ring complex. The carbonatites might be accompanied by various mineralizations of Nb, Ta, P, REE, F, Ba and etc. Carbon and oxygen isotopic studies show that most of carbonatites are derived from the mantle, and they are in agreement to the associated mafic ultramafic rocks in C and O isotopic features. The initial Sr ratios of carbonatites are similar to that of mantle, except for some due to the crustal contamination. In combination with experimental petrology, fluid inclusions and the property of CO 2 H 2O NaCl fluid system, the carbonatitic magma is inferred being generated from the mantle except for those of re melting type. The CO 2and H 2O play an important role in the generation and formation of carbonatitic magma during metasomatism and partial melting in the mantle. The investigation on melt/fluid inclusions of carbonatites revealed a whole evolutional order from magmatic to hydrothermal stages. Experimental studies confirmed the evolution series from early magmatic system typical with K, Na, Ca and Mg to the hydrothermal system with alkaline ions such as Na and K. The fenitization of wall rocks occurred in later hydrothermal stage. The formation of carbonatites includes at least three stages: the magmatic crystallization stage, the post magmatic (gaseous carbonatitic) stage, and the metasomatic carbonatitic stage. And the mafic, ultramafic and alkaline rocks, closely related to carbonatite in space and origin, are suffered the immiscible phase segregation, the differentiation of magma, the crystallization and the fenitization.
出处
《地球科学进展》
CAS
CSCD
2001年第4期501-507,共7页
Advances in Earth Science
基金
国家攀登计划预选项目"Pb
Zn大规模爆发性成矿"(编号 :95 -预 -2 5 )资助
