Dynamics Setting Of Sunwu-jiayin Basin And Its Influence Of Mineralization

Dynamics setting of basin is a hot area in geology research,and it’s one of the most importantbasic research subject in petroleum，rock gas and mineral deposit. Sunwu-Jiayin basin lies in northof Songnen landmass.The east border of the basin is the Jiayin-Mudanjiang fault and adjacent toJiamusi landmass. The west border of the basin is the Erlian-Heihe suture zone and adjacent toHinggan landmass. South-Southwest of the basin and the Song liao basin are divided by the XiaoHinggan Mountains.The basin is linked together with Jeya-Breya basin. volcanic formationdeveloped in Early Cretaceous Epoch in Sunwu-jiayin basin. The volcanic rocks mainly composeof basalt, basaltic trachy andesite,andesites,trachy dacite.Most of they belong to high kaliumcalc-alkalic series. Alkalic rhyolite developed in Later Cretaceous Epoch in Fu minhe formation，and it belonged to potassium kuroiwa series.Analyzing the tectonic setting through geochemical characteristics,information of areageology and field research. SiO₂occupy51.86%～64.24%in oxide in volcanic rock. Volcanicrock samples have relatively high alkali（4.25%～7.50%）contents, relatively low TiO₂2（0.26%～1.3%）contents.The value of K₂O/Na₂O is0.39～0.73,and the value AR variation range from1.4to2.21,it implys that the volcanic rocks has formed in active continental margin. basaltic trachyandesite and andesite both belong to low magnesium andesite which always appears on inland sideof active continental margin. Volcanic rock samples have medium rare earth elements(65.54×10^-6～126.06×10^-6)，and the value of（La/Yb）Nvariation range from0.39to0.73, withweak Eu anomalies and Ce anomalies. These samples are enriched in LILE（Rb、Ba、K、Th、U）and Pb but relatively depleted in HFSE（Nb、Ta、Y、Yb、Lu）and Ti、P、Sr.The value of Th/Hf、Ta/Hf、La/Nb、Nb/Zr of calc-alkalic basalt respectively range from0.28～1.52、0.12～0.27、8.76～10.33、0.06～0.07，which imply the trait of both within plate basalt and calc-alkalicbasalt.The calc-alkalic basalt are enriched in LILE，which is related to the accession of oceansedimentary contents on subducted oceanic crust. Strontium anomalies is related to hybridizationof magma and continental crust in the process of the rise of magma.Anomalies of Nb、Ta、Ti、P isrelated to the accession of oceanic lithosphere contents during partial melting of calc-alkalicbasalt. SiO₂of Alkaline rhyolit occupy71.54%～72.4%in Fu minhe formation in Later CretaceousEpoch，the samples have high alkali（11.77%～12.2%）content，belong to high kalium series（K₂O occupy5.15%～5.36%）. The value AR variation range from9.34to10.38. Alkalinerhyolit samples have high rare earth elements(198.27×10^-6～336.01×10^-6)，and the value ofLREE/HREE variation range from5.44to6.82.The value of（La/Yb）Nvariation range from4.14to6.23, with weak Eu anomalies. Alkaline rhyolit are enriched in LILE （K、Rb、Ba、Tu、U），and a little enriched in HFSE（Nb、Ta、Zr、Hf）but relatively depleted in Sr、P、Ti,with Rb、K、Pb、Zr、Hf positive anomalies and Sr、P、Ti negative anomalies,which implicated that themagma had being infected by upper crust during ascending. Alkaline rhyolit in Later CretaceousEpoch have high K₂O than volcanic rocks in Early Cretaceous Epoch，what shows timepolarity,and it implicate that the continental crust are thicker and have more contents ofcontinental crust in Later Cretaceous Epoch than Early Cretaceous Epoch.These traits show thatvolcanic rock in Sun wu-jia yin Basin have the same character of arc volcanic.The proposed analysis indicates that the volcanic rocks in Early Cretaceous Epoch areprovided with the traits of volcanic rocks in both continental and active continental margin,andthey are volcanic rock seriels which on the inland side of the active continental margin.Sunwu-jiayin Bsin suffered multiple tectonic events during formation in the same period.Pacific plate subducted in NW were major dynamic source of the formation of Sunwu-jiayin Bsinin Early Cretaceous Epoch.It coursed mantle diapir of the study area，and made it in tension stressfield,which formed graben basin along NNE.Sun wu-jia yin Basin was formed on the activecontinental margin，which induced by subduction of the Pacific plate in Early Cretaceous Epoch.There are many epithermal gold deposits in the basin，and there are many faults whichcontrol the mineralization in each deposits.The author have investigated Gaosongshan golddeposit in this paper，and chosen12ore samples，12country rocks samples，60samples in upperlayers.12elements（Au、 Ag、Cu、Pb、Zn、Co、As、Bi、Hg、W、Mo、Sn）havebeing analyzed by correlation analysis, factor analysis and cluster analysis with the help ofSPSS.The ore element assembly in Gaosongshan deposit can be divided into3groups：（Au、Ag、Pb、Mo、Hg）,（W、Zn、Co、Cu）,（Sn、Bi）,As.The elements assembly of ore samples aredifferent from elements assembly of samples in upper layers and country rocks samples.Volcanicbreccias in Banzifang formation is one of the country rocks，which are contained200times moregold than samples in upper layers.The main ore conducting structure are faults along NE whichproced by simple shear what is the result of asymmetry extend.Faults along EW、NNE and NNWassociated with faults along NE are main ore-bearing structure.