Study On The "White Smoke Stype" Of Lacustrine Exhalative Rock In The Xiagou Formation Of Qingxi Sag Of Jiuxi Basin

On the basis of summarizing and comparing with the latest research results of hydrothermal sedimentary rock both at home and abroad and the existed research results of the research district, adopting the analysis means of mineragraphy, petrofacies and geochemistry, etc. and combining with relevant speciality-theory knowledge, the author carries on overall and deep research for extensively distributed lacustrine laminated dolomitic mudstone and muddy dolomite in the Xiagou Formation, Lower Cretaceous of Qingxi sag of Jiuxi basin. The results show:a)The lacustrine "white smoke type" exhalative rock is characterized by the special mineral assemblage including rich claysized-albite and ankerite, a small amount of quartz, analcite, barite and dickite and microcontent iron pyrites, galena, chalcopyrite and blende. Above-mentioned hydrothermal minerals have certain intergrowth assemblage regularity.b)This exhalative rock is mainly characterized by microcrystallite-aphanocrystalline texture and laminated structure, and also shows hydrothermal fragmental texture, hydrothermal brecciated texture, spiral vortex structure and so on. From hydrothermal vent to the margin of basin, the exhalative rock has a depositional spread regularity: filling lode rock type→water bursting breccia type→basin depositing type →region diffusing type.c)The hydrothermal fluid is mainly high alkaline hot brine including poor metal sulphide and rich microelements of CO₃^-2, SO₄^-2, Cl^-1, Ca²⁺, Mg²⁺, Fe²⁺, Si⁴⁺, Al³⁺, Na⁺ and mantle reservoir microelement of Zn,Rb,Mo,As,Ni,Co,Sb,Ba and Ag.The hydrothermal fluid activity is relative to volcanic eruption and geothermal anomaly by Lower Cretaceous extensional fault controlled in Jiuxi basin.north-east secondary fracture zones offer the good pathway for the flow and eruption of hydrothermal fluid. The geothermal gradient caused by volcanic activity offers the power for the flow of hydrothermal fluid.d)The author denies the viewpoint about the genetic analysis of the exhalative rock that extensively distributed lacustrine laminated dolomitic mudstone and muddy dolomite came from deposition processed...