碳酸岩岩浆作用过程的包裹体研究

碳酸岩是一种富含碳酸盐矿物(方解石，白云石，铁白云石等＞50％以上)的火成岩。通常以侵入的方式，与超基性岩和碱性岩共生，位于环状侵人体的中心部位；或以喷出的方式，与碱性岩等构成环状杂岩体。碳酸岩在喷出或侵入过程中，与上部地壳围岩发生以富含碱质(钠或钾)为主的蚀变作用，形成特征性的蚀变岩石——霓长岩。通过对碳酸岩中的包裹体研究，可以获得包括成岩成矿时的温度、压力、密度、流体组分、流体演化等大量信息。碳酸岩矿物中包裹体的研究已取得很大进展，并为了解碳酸岩岩浆演化性质和特征提供了许多重要的信息：(1)碳酸岩可以形成于流体和熔体两种介质条件下；(2)碳酸岩矿物中包裹体富含CO2；(3)在碳酸岩的起源和演化过程中伴随有岩浆的不混溶作用发生；(4)碳酸岩岩浆具有的较低的粘度和密度。为了保证对从碳酸岩中获得的包裹体资料的合理解释，在研究过程中必须结合碳酸岩产出的大地构造背景、典型岩石组合、典型蚀变岩石(霓长岩)、赋存的矿产特征等方面的资料。虽然目前在包裹体研究方面尚有许多不足，但作为自然界唯一能够保存有原始成岩成矿流体的地质样品，包裹体的研究具有其他方法不可替代的作用。

Fluid Inclusion Study Related to Cabonatitic Magmatic Process

Carbonatite is a light grey or offwhite igneous rock rich in carbonate minerals (calcite, dolomite, ankerite etc., above 50%). It is often associated with ultramafic and alkaline intrusives, being located in the centers of the ring intrusions; or is associated with alkaline extrusives as ring complexes. During its intrusions or extrusions, there often happens fenitization, a type of alkali rich (Na or K) wall rock alteration between carbonatite and wall rocks. By studying the fluid inclusions in carbonatites, we can obtain much rock forming and ore forming information, such as temperature, pressure, fluid density, fluid compositions and fluid evolution etc. Fluid inclusions study is an effective means to acquire information related to characteristics of volatiles in carbonatites, immiscibility features, viscosity, density and origin of carbonatite magmas etc. Results of fluid inclusion studies indicate that: (1) Carbonatite can be formed at magmatic to hydrothermal conditions. (2) CO 2 is the most abundant component of volatiles. At the later stage of carbonatitic magma evolution, CH 4 may appear as one of the major components of volatiles. (3) Immiscibility between carbonatite melt and silicate melt has been identified by fluid inclusion study which implies existence of independent carbonatitic magma. (4) Carbonatitic magma has low viscosity and density, which enables its easy propagation at shallow crustal levels through fissures and veins. Fluid inclusion study plays an important role in the study of carbonatite petrology and metallogenesis. It can provide unique data to help us to get better understanding of carbonatitic magmatic process and related mineralization.