【摘要】 <正> 本文是笔者对云南基性超基性岩及其有关矿产进行多年野外调查的基础上,搜集了有关的1:20万区域地质调查资料、矿产普查勘探资料以及部分有关文献进行了野外和室内研究作出的成果。笔者认为已有文献资料对云南“三江”地区基性超基性岩在岩带划分、侵位时期和形成环境等方面的认识多不一致,值得进一步研究。更多还原

【Abstract】 The basic, ultra basic rock masses of "Three River" (Nu Jiang, Lancang River, Jinsha River-including Yuanjiang River to the south of it) area in Yunnan are characterized by having the stripped distribution, concentrating in several segments, occurring in group, the single rock mass being small and showing obvious metallogenic specialization. They can be divided into 9 rock belts-Luxi, Changning-Menglian, Lancang River, Deqin, Jinsha River, Amo Jiang-Lixian Jiang, Ai Laoshan, Jinping and Dali-Midu. Within the tectonic zone developed on the basis of the Xingkai cycle, any profile of more complete, convincing ophiolite suite hasn’t been discovered up to now. No volcanic activity was found in Lower Palaeozoic but there were the volcanic-sedimentary formations of shallow-sea, transition or terrestrial facies in Upper Palaeozoic and Mesozoic. The most part of rock chemistry belongs to the alkalic and high-alumina sequences, only a few to the tholeiitic sequence, being unlike the volcanic rocks formed in the mid oceanic ridge. Most basic and ultrabasic rock masses occurred separately within the Luxi, Deqin, Jinsha River and Ai Laoshan rock belts predominantly consisting of the magnesian ultrabasic rocks, judging from the rock association; while the basic and ultrabasic rocks usually occurred together and showed the concentric girdle structure in ferruginous ultrabasic rock belt. The lherzolite and clinoperidotite all display the idiomorphic-hypidiomorphic or xenomorphic textures, the poikilitic texture and the pseudoporphyritic unequigranular texture. With respect of the contact relations between the rock masses and the country rocks, the tectonic contact and the intrusive contact were all found, and the alteration-metamorphic phenomena comprising the hornfelsization, talc carbonatization, chloritization and the serpentinization were commonly seen. The sequence of the magmatic activities was: the extrusive rocks first, then intrusion and extrusion of the basic rocks, subsequently intrusion of the ultrabasic rocks, finally cut by the basic veins. Most of the distribution pattern of rareearth elements belongs to the concentration’ type, only individual rock group (or mass) to the even or the deficient type. From what is said above, the volcanic, basic and ultrabasic rocks, "Three River" area of Yunnan, don’t possess the features of an oceanic crustal texture, are not the relict fragments of the ophiolite suite located at the subduction zone, formed in the mid oceanic ridge. They might be the products of the rift valley zone developed from a folded belt along the continental margin.更多还原