一种特殊类型的夕卡岩—镁铝夕卡岩的矿物特征

在研究我国河北省邯邢铁矿的过程中,发现了一种矿物组成比较特殊的夕卡岩。其组成矿物主要有富铝透辉石、绿脆云母、尖晶石、钙镁橄榄石、钙铝榴石、富铝角闪石、硅硫磷灰石、及蓝色方解石等。与我国常见的钙夕卡岩及镁夕卡岩有明显不同。它作为一个早期独立的阶段分布在各矿区,因其组成的矿物中富含镁、铝,故名“镁铝夕卡岩”。其后期的热液蚀变产生了众多的罕见矿物如雪硅钙石、碳硅钙石、吉水硅钙石、硅灰石膏等及大量沸石类矿物,但无石英,酷似基性火山岩的蚀变产物。矿物学研究表明,这种夕卡岩形成于一种富镁、铝而SiO_2不饱和的地球化学环境和高温低XCO_2的条件。

The Mineralogical Characteristics of an Unusual Type of Skarn-"Mg, Al-skarn

There axist an unusual type of skarn occurring as an early independent stage of the Hanxing type iron deposit in Hebei province. It is characterized by consisting of minerals riched in aluminium and magnesium such as Al-diopside, grossularite, clintonite, monticellite, spinel, Al-amphibole, vesuvianite, corundum, hibonite, wilkeit and blue calcite and obviously in composition different from those of normal skarns (i. e., Ca-skarn and Mg-skarn) in China, so that the "Mg,Al-skarn" is properly named.On the late stage of hydrothermal alteration for Mg,Al-skarn, many of the rare minerals and zeolitic minerals are formed, such as tobermorite, scawtite, gyrolite, gismondine, wilkeite, thomsonite, heulandite, stilbite and apophyllite etc., of which the mineral association are similar to the products in hydrothermal alteration of basic eruptive rocks.The mineral evidence given in this paper indicate that the skarn form at a Mg-rich, Al-rich and SiO2 under saturation geochemical environment as well as high temperature and low-XCO2 condition.