Research On Tectonic And Magma Space-Time Evolution And Genesis Of Gold Deposit During The Early Cretaceous In The Eastern Jiaodong Peninsula

Jiaodong Peninsula has been the hot area of geoscience research.This article is to explore the eastern region of Jiaodong from 4 aspects: regional geology,tectonic magmatic evolution,gold potentiality and tectonic significance.In the part of regional geological background,the study area is located in the boundary of North China craton and Dabie-Sulu belt.In Early Cretaceous tectonic transition period,the dynamic background in the region is from extension transfer to the large-scale strike slip transitions.The formation,magma,structure are different from the western area of the peninsula.It also reveals that the two part of Jiaodong are different in the tectonic evolution of the tectonic transition period.The second part is tectonic and magma evolution in space and time,Since the mid-late Jurassic,intense tectonic and magma evolution began in the region.Wendeng and Kunyushan granite(170-130Ma)are in the late Jurassic and early Cretaceous,normal faults based on the background of extensional tectonics.This is the direct evidence of tecton-dome-magmatic detachment.During the early Cretaceous(130-120Ma),the research area is in the stage of strike slip thrusting of the crust and lithosphere,Shidao fault as a representative.And at this time the Rongcheng-Weihai block has a counter-clockwise rotation;In the late Early Cretaceous(120-100Ma),regional large-scale magmatic and volcanic activity were frequent,such as WDS granite,wide spectrum dikes(WSDS)and volcano eruption at the east side of Lidao fault,and the 3D evolution model is established.In the part of gold potentiality,Jiaodong Peninsula is the important gold producing area in China,from the west(Gulf of Laizhou)to the east coast the number and scale of gold deposits shows a decreasing trend.The quartz veins which contain gold often constitute a duplex system in the study area;the semi-brittle deformation isthe main deformation;gold mineralization time is about 125-115Ma;the three generation characteristics of quartz grains were revealed by the study of the micro-structure of quartz,they are early coarse grains(I),meta-phase medium grains(II)and late fine grains(III),the corresponding temperature are 240 ~ 390?,270 ~180?and < 210? respectively,gold deposits mainly concentrate in the two stages of I(early)and II(meta-phase),and the temperature is concentrated in 320 ~ 220?.The last part is geotectonics,regional magmatite rock geochemistry and tectonic chronology study reveals the study area is dominated by S type granite in the late Jurassic and early Cretaceous(170-130Ma),it also reveals the dynamic background of the area is tectonic extension and detachment faulting;Jiaodong block uplift and denude violently in the early Cretaceous,the evidence from chronology reveals the block had a counter-clockwise rotation.The research area is dominated by I type granite,in the late Early Cretaceous(120-105Ma),this reflects the source of magma is mixed by crust and mantle,The upper mantle material joined in the mid-stage super-crust-scale strike slip activity.