【摘要】 广西元宝山区的层状基性-超基性岩带是桂北花岗-绿岩带的超镁铁质熔岩,其岩石化学特征与科马提岩相似,与之有成因关系的矿产,不仅有铂钯矿,还有具很大经济价值的锡矿。后者是一种新型锡矿床,与产于花岗岩内外接触带的锡矿完全不同,它产于基性-超基性杂岩之内,呈层状产出,随地层褶曲而褶曲。矿物组合、地球化学特征均与超基性岩有密切关系,但受到后期热液(含花岗岩事件所产生的热液)的叠加改造作用。更多还原

【Abstract】 There are 200 basic-ultrabasic bodies of Yuanbao mountain. They are layered and divided into three zones: west, middle and east, which have been folded along with surrounding rocks. They are characterized by the rhythmic units consisting of basic-facies, ultrabasic-facies and mid-basic pyroclastic bed which retaines the pyroclastic textures and the cross bedding.The ultrabasic-facies, which constitutes a principal proportion of basic-ultr- abasic rocks, belongs to the harzburgite-websterite series. There are the cumulative textures and the chilled margin in their border facies. The petrochemical characteristics of the rocks are as follows: Na₂O+K₂O<0.5%, K₂O<0.1%,TiO₂<1%, CaO/Al₂O₃（most）=0.45-1.15. The rocks are roughly similar to the ultramafic komatiites.The middle zone contains a high content （70 ppm） of tin in the central facies of ultrabasic rock and local concentrates occur in the border facies forming the ore bodies. The mid-basic pyroclastic bed has strongly mineralized. The tin ore is as thick as 1-20m belonging to a type of cassiterite-sulfide. The tin deposits had been formed by following geological processes. The tin-bearing magma from the upper mantle is liquation-defferentiated first producing a tinbearing or tin-rich unltrabasic and basic magma. With the magma erupting crystallization-differentiation and hydrothermal activity mobilized the oringiual enrichment, as a result, the tin deposits formed.The ultrabasic rock of the east zone has a high content of platinum （up to 0.04 g/t） concentrated to the border facies to form ore. The platinum ore was formed by the magmatic crystallization and the mobilizing of the hydrothermal solution.更多还原