Full-Text Search:
Home|About CNKI|User Service|中文
Add to Favorite Get Latest Update

Geochronology and Geochemistry of Sungezhuang Alkaline Complex in Jixian County,Tianjin

CAI Jian-hui1,YAN Guo-han2,MU Bao-lei2,RENG Kang-xu3,LI Feng-tang2,YANG Bin2 1.Institute of Mineral Resources,Chinese Academy of Geological Sciences/MLR Key Laboratory of Metallogeny and Mineral Assessment,Beijing 100037,China 2.School of Earth and Space Sciences,Peking University/The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education,Peking University,Beijing 100871,China 3.Research Institute of Exploration and Development,Tarim Oilfield Company,PetroChina,Korla 841000,Xinjiang,China  
Zircon SHRIMP U-Pb age(225.6±1.1) Ma of alkaline syenite from the Sungezhuang alkaline complex in Jixian County of Tianjin is reported for the first time,which suggests that the complex is a product of Late Triassic alkaline magmatism.A systematic study on the composition of major element,trace element,REE of the alkaline syenite and ortho-pyroxenite from the complex reveals their lithogeochemical feature,source material,tectonic setting and geological significance.According to the bulk compositions,the syenite has high Al,low Ca,Fe and Mg content with aluminum over-saturation,and the ortho-pyroxenite has high Ca,Fe and Mg content.Both are characterized by enrichment in alkaline with K2O/Na2O1.It is suggested that the Sungezhuang alkaline complex is resulted from the magmatism in a post-orogenic setting.These rocks are all of high REE content,LREE enrichment,HREE depletion and no obviously Eu anomaly.In the PM-normalized diagram,trace element diagram exhibits LILE(Sr,Ba) and LREE(La,Ce,Pr,Nd,Sm) enrichment,relative depletion in HFSE(Nb,Ta,Hf and Th) with negative U,Nb,Ce and Ti anomalies.Furthermore,transitional element(Cr,Ni and Co) contents in the ortho-pyroxenite are relatively low,which implies that the Sungezhuang alkaline complex has a deep magma source related to enriched mantle.The comprehensive research on Indosinian alkaline intrusive belt in northern margin of the North China craton shows that the emplacement ages of these alkaline complexes range from 238 Ma to 220 Ma.It can speculate that the geodynamic setting of large-scale Early Mesozoic alkaline magmatism in northern margin of the North China craton and destruction of the North China craton,specially lithospheric thinning in North China,are basically the same.The Early Mesozoic alkaline rocks(238-200 Ma) is possible to represent the beginning of lithospheric thinning in North China.Moreover,the lithospheric extension and thinning in northern margin of the North China craton may start from the western section.
Download(CAJ format) Download(PDF format)
CAJViewer7.0 supports all the CNKI file formats; AdobeReader only supports the PDF format.
©CNKI All Rights Reserved