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新疆三塘湖地区二叠系芦草沟组与新疆广大地区的芦草沟组同为重要的生烃层系.本研究首次在三塘湖跃进沟剖面芦草沟组中发现热液喷流型白云岩及其共生组合,白云岩以泥晶白云岩和砂屑白云岩为主,含少量砾屑白云岩,它们多呈0.05～0.15cm厚的纹层,与纹层状泥晶灰岩和纹层状泥晶白云质方沸石岩等呈互纹层.砂屑白云岩中普遍含碱性长石和方沸石颗粒,为方沸石响岩—过碱性岩浆岩经喷爆、搬运、沉积而成的矿物碎屑;基质多为小于0.01mm的白云石和铁白云石.根据矿物成分和含量可将白云岩分为4种类型.依据白云岩中所含的碎屑均为方沸石、碱性长石、凝灰岩的晶屑、玻屑等内碎屑,认为该湖盆应是一种以内碎屑为主的欠补偿湖盆.岩石地球化学结果显示:氧同位素■18OPDB介于-5‰～-21.1‰,平均-11.9‰;87Sr/86Sr比值介于0.70457～0.706194,平均0.705005,结合多期过碱性岩浆岩的溢流,反映出地幔热液的特点.来自地幔的流体使底辟到下地壳的超基性岩发生蛇纹石化,提供了生成白云石、铁白云石所必须的Mg2+,Fe2+.过碱性岩浆以及富含Ca2+,Mg2+,Fe2+和CO32-的热液交替喷发和喷流,并与湖水混合,最终在热液喷口处形成岩浆喷爆角砾岩、具同生变形层理的白云岩,在远离喷口处形成具纹层构造的白云岩等喷流岩.综合资料分析表明,本区的白云岩是一种罕见的陆内伸展背景下的裂谷盆地地幔热液喷流型原生白云岩;该套岩石的发现无论对白云岩成因的认识还是对于探讨新疆北部晚古生代的区域构造背景及沉积环境均具有重要的科学意义.
The Permian Lucaogou Formation in the Santanghu area of Xinjiang Autonomous Region is also an important hydrocarbon generating layer with the Lucaogou Formation in the vast Xinjiang Uygur Autonomous Region.This study is the first to find hydrothermal jets in the Lucaogou Formation at the Yuejugou Section of Santanghu Lake Type dolomite and its symbiotic assemblage. The dolomite is mainly composed of dolomite and dolomite with a small amount of gravel dolomite, mostly of 0.05-0.15cm thick layer, with laminar micrite And lamellar-shaped dolomitic dolomitic meshed zeolite rocks are interbedded layers.The sandy dolostone generally contains alkaline feldspar and analcime particles, for the zeolite rock - over alkaline magmatic rocks by blasting, handling, sedimentation Of the mineral debris; matrix mostly less than 0.01mm dolomite and iron dolomite dolomite can be divided into four types according to the mineral composition and content.According to the dolomite contained in the debris are analcime, alkali Sex feldspar, tuffaceous tuff, vitreous and other debris, the lake basin should be considered as an intra-clastic mainly under-compensated lacustrine rock geochemistry results show: oxygen isotope ■ 18OPDB between -5 ‰ ~ -21.1 ‰, the average -11.9 ‰; 87Sr / 86Sr ratio between 0.70457 ~ 0.706194, an average of 0.705005, combined with multi-phase over-alkaline The overflow of the mudstone reflects the characteristics of the mantle hydrothermal fluid from the mantle that serpentinizes the ultrabasic rocks from the diapir to the lower crust and provides the necessary Mg2 +, Fe2 + for dolomite and iron dolomite formation. Over-alkaline magma and hydrothermal alternating eruptions and jet streams rich in Ca2 +, Mg2 +, Fe2 + and CO32- were mixed with the lake water to form magma explosive rocks at the hydrothermal vents, with symbiotic deformable bedding Dolomites, jet-lava dolostones with a textured layer are formed far away from the spout.Comprehensive data analysis shows that the dolomite in this area is a rare intra-hydrothermal jet flow in the rift basin The discovery of this set of rocks, regardless of the genesis of dolomite, is of important scientific significance for exploring the regional tectonic setting and sedimentary environment of late Paleozoic in northern Xinjiang.