内蒙古哈达庙含金侵入杂岩体稀土元素地球化学研究

GEOCHEMISTRY OF RARE EARTH ELEMENT IN THE HADAMIAO GOLD-BEARING INTRUSIVE COMPLEX, XIANGHUANGQI, NEI MONGGOL (INNER MONGOLIA)

本文利用哈达庙含金侵入杂岩体各主要岩石类型REE分析数据,结合野外地质产状和地球化学特征,论证了杂岩体REE贫化、富集规律与成岩岩浆结晶演化的关系.在此基础上,提出了成岩过程早期以矿物结晶分异作用为主,而晚期阶段受热重扩散效应制约的成岩模式,二种分异作用的交替进行为金矿床的形成提供了物质基础.同非金斑岩体热液蚀变岩相比,含金斑岩体的热液蚀变岩以LREE丰度明显增高为特征,其独特的分布型式和组成特点可作为该区斑岩体含金性评价的地球化学标志之一.

The systematic analysis and the patterns of REE of mjor rock phase from the Hadaminjo intrusive complex are presented here, which furnish further evidence for rock-forming process.1. The REE patterns of major rock phase from the complex all exhibit a rightward decline curve with a faint negative Eu-anomaly. REE content increases progressively from dioriteporphyrite (58.52ppm) through quartz diorite (110.888ppm) and cryptoexplosion volcanic breccia (108.55ppm) to granodiorite (134.38ppm) and grannodiorite porptwry (134.01ppm), whereas dropped distinctly from granodiorite porphtry to graniteporphyry (96.93ppm). It was suggested that the former is attributed to mineral crystalline differentiation of magma, the latter is the result of integrate effect of multiple differentiation.2. The REE content increases from unaltered to altered rock sample in the Hadamio gold - bearing graniteporphtry. Conversly, REE content has obviously depletion from unaltered to altered rock sample in Yihenwusu gold-free granodiorite porphyry.3. The REE patterns of rhyolites (REE = 390.65ppm) has a v-shaped curve with a strong negative Eu anomaly. Study shows that rhyolite is quite different form the complex on their original magma.In term of these REE characters, isotopic data and other geological evidences, it has been suggested that rock-forming material was originated mainly from the partial melting or anatexis of proterozoic basement 1300Ma. ago. Major rock phase of the complex were formed at different evolutionary stage of a comagma. REE patterns of the gold - bearing altered rocks from the graniteporphry can be taken as an indicator for gold prospecting in this area