川南地区晚二叠世含煤建造及玄武岩浆活动与裂谷发育阶段耦合

Coupling of Late Permian Coal-bearing Formation,Basalt Magmatic Activities and Rift Development Stage in Southern Sichuan

川南地区晚二叠世是裂谷发育重要阶段,研究认为玄武岩浆活动与挠曲盆地和前缘隆起的勾联,建立了玄武岩浆喷溢韵律旋回与含煤地层四级层序与三级层序的对应关系;本区晚二叠世聚煤环境属潮坪环境,是在总的海侵及区域聚煤背景条件下,由海侵、基底升降和聚煤速率共同作用来造就聚煤可容空间,本区前缘隆起即基底上升,能协调三者造就有利的聚煤可容空间;“古蔺-桐梓前缘隆起”“叙永-习水前缘隆起”“筠连-珙县前缘隆起”为聚煤奠定了有利的地形条件,成为聚煤中心;前缘隆起最高部位西侧是“滨岸湖泊”或“海漫湖泊”与煤质关系密切。该区上二叠统煤层主要属高阶煤,玄武岩浆喷溢活动有3个旋回,28个韵律,每次喷溢的熔岩被体积宏大,热容量巨大,从西到东玄武岩岩被连续,只有厚薄之别,既是高温熔岩热能传导者,也承接储蓄热能,使其成为高温异常区,是高阶煤形成的主要原因。

Late Permian Epoch of southern Sichuan area is an important stage of rift development.Studies have considered that the basalt magmatic activities colluded with flexural basin and frontal uplift established correspondence between rhythmic cycle of basalt magmatic outpouring and coal-bearing strata fourth-order sequence and third-order sequence.Late Permian coal accumulation in the area belongs to tidal flat environment,under the general transgression and regional coal accumulation setting,brought up coal accumulation accommodation space by transgression,basement elevation and subsidence,as wall as coal accumulation rate combined actions;front uplift i.e.basement elevation in the area can coordinate the three to achieve favorable coal accumulation accommodation space.The Gulin-Tongzi,Xuyong-Xishui and Junlian-Gongxian front uplifts have laid down favorable relief condition for coal accumulation and become coal accumulation centers.The west side of front uplift highest position has been littoral lake or apron lake close related with coal quality.Upper Permian coal seams in the area mainly belong to high ranked coal;basalt magmatic outpouring activities have 3 cycles,28 rhythms,every outpour lava bed has large volume and large thermal capacity.From west to east,basalt bed is continuous,only thicknesses different.It has been high temperature magmatic thermal energy transmitter,also undertaken and accumulated thermal energy turned into high temperature abnormal place,and the main reason to form high ranked coal.