The Middle Early Cretaceous Tectonic Events In Southeast China Inland Area And Its Geological Significance

Large scale continental deformation and igneous province in the southeast of China during the Mesozoic Era,To provide an ideal place for the study of tectonic processes and continental deformation.Sanbaishan basin and Banshi basin in Southern region of Jiangxi,the southeastern inland of China,The basin consists of Early Cretaceous volcano rocks of Wuyi group,The volcanic series unconformably covered the Nanhua-Cambrian metamorphic rocks,and by in the early stage of Early Cretaceous Epoch Guifeng group or Luo Tang group red sedimentary rocks unconformity cover.In the Sanbaishan basin,Sinian metamorphic rock nappe in Wuyi group of Ehuling formation volcano rock,Forming a plurality of klippe.In the Banshi basin,Development of thrust fault,Sinian metamorphic rocks overthrust Ehuling group volcanic rocks on top,And the internal of metamorphic rock development of thrust fault and Continuous deformation occurred fold;Shixi formation of Wuyi group Stratigraphic development of fold structures, Stratigraphic occurrence up-right to overturned folds,And the development of mudstone flexure structure quite,And a deterioration phenomenon of silicified.These phenomena show, Wuyi group volcano rocks in Gannan area occurred after the formation of strong tectonic events.Baibu formation of Luo Tang Group Conglomerate Stratum unconformity on top of the Sanbaishan basin Wuyi group volcano rocks and Hekou formation of Guifeng Group Conglomerate Stratum unconformity on top of the Banshi basin Wuyi group volcano rocks,Having a near source rapid piled characteristics,Tectonic deformation weak;Huichang basin on the eastern side of Banshi basin,rocks from the Luotang Group exhibit weak deformation and include a layer of basal conglomerate indicating rapid erosion and proximal deposition,the intercalated trachyte within the Luotang redbed show the geochemical affinities with the adakitic rocks and high-pressure tracheae.These phenomena show that compressional tectonic event occurred in Gannan region after the formation of the Wuyi group volcanic rocks, before Luotang group red sedimentary rocks formed.Volcanic chronological data shows,The Rhyolite of Shixi formation and Tuff of Ehuling formation SHRIMP zircon U-Pb ages of 130.8 ± 0.7Ma and 142.6 ± 1.0Ma of Wuyi group in Banshi basin,The Trachyte of Ehuling formation SHRIMP zircon U-Pb ages of 141.6±0.96 Ma of Wuyi group in Sanbaishan basin,The Trachyte of Baibu formation SHRIMP zircon U-Pb ages of 110.7±1Ma of Luotang group in Huichang basin?Combined with a general lack of the middle Early Cretaceous strata in Gannan,Description compressional tectonic event occurs after 131 Ma, before 111 Ma.Tectonic metamorphic geochronology data show,Banshi basin overthrust newborn mineral sericite,K-Ar age of dilution method 118.21 ± 3.21Ma;Sanbaishan basin Overthrusts metamorphic rocks klippe bottom,K-Ar age of dilution method 112.90±3.65Ma;Indicates compressional tectonic event occurred between 118 ~ 113 Ma.early stage of Lower-Cretaceous(145-130Ma)in Southeast China inlandwidely developed high-K calc-alkaline volcanic-intrusive rocks,Later period of Lower Cretaceous- early stage of Upper-Cretaceous(110-90Ma)widely developed in mafic volcanic rocks,The former constitute volcanic-intrusive rocks belt in main body,The latter is often sandwiched between the bottom of the red sedimentary rocks.And the middle Early Cretaceous(130-110Ma)also volcanic- intrusive activities of relative calm,Suggesting that its construction environment is different from the early stage of Lower-Cretaceous transition from compression to extensional tectonic setting,There are also differences between Later period of Lower-Cretaceous to early stage of Upper-Cretaceous with Strong extensional tectonic environment.Kinematic Character display,Southeast China inland the middle Early Cretaceous compressional stress direction NW-SE direction,And Southeastern China continental margin squeeze squeezing stress tectonic events have the same direction in the middle Early Cretaceous,We tentatively propose that this deformation resulted from remote response to the plate subduction established along the coastal region of the southeastern China.The middle Early Cretaceouscompressive tectonic events Confirm in Southeast China inland,Combined with previous confirmation of Middle Jurassic compressional tectonic events,Yanshan tectonic evolution of the Southeast China inland has a tensileextruded multi-cycle characteristics "accordion" type provides a full and strong geological evidence,Metallogenic tectonic setting analysis should take into account the impact extrusion tectonic events also Provides the basis.