The Geological And Geochemical Characteristics And It’s Petrogenesis Of Zhangyuan Basite In Pingdu County Of Anhui Province

Zhangyuan Mafic Tectonic Melange Belt, located in Xiuning County, Anhui Province spreads from the northeast to the southwest, along the belt from Yaoli, Hecheng to Jiangtan. It forms in the second and third rock section of the Mukeng group in the form of structural fragments or mere fragments, with its major rock constitution includes massive grabbro, disbase and pillow basalt. Here, the researcher carries out researches on geochronology on the grabbro, and has done petrographic studies on the lithology of three rocks, as well as researches on the principal element, microelement and lanthanon element. At the same time, the researcher raises his suggestion on its tectonic structure environment and completes the comparison research with Fuchuan ophiolite suite.Researches show that the three rocks all suffer from intense erosion and tectonic deformation. Besides, general piagioclase sodium zoisitization, chloritization, sericitization, pyroxenewith sodium zoisitization, chloritization, uralitization and visible chlorite rotating porphy roclasts can be found in the rocks.In the TAS chart of the major elements, it can be seen that most rocks belong to the basalt region, belonging to alkaline rock series and tholeiite series.The research on the trace elements shows that the rock is rich in LILE, but the compatible element Cr and Ni suffer from severe loss in the rocks and. The mean value of Zr/Hf ratio in the rocks is 36.11, which is similar to the Ocean Island basalt (35.9).The standardized chart of the rocks’REE and chondritic meteorite shows the right leaning type of negative anomaly of Eu, with a higher content of light lanthanon than E-MORB which is rich in light lanthanon as well as N-MORB which lost light lanthanon. Thus, it is suggested that it might be island arc basalt or continental margin basalt.With the zircon LA-ICP-MS U-Pb dating of the gabbro in Zhangyuan mafic tectonic melang. It is found that its diagenetic age is 998±5.6Ma. With the studies on the tectonic structure environment and cause of formation over the rock anti-erosion microelement, it is found that its formation environment is island arc and it comes from the primitive mantle, with weak assimilation contamination effect.At last, a comparison research is done between its geological feature, its major element, trace element,REE, its formation age and its structure environment with those of Fuchuan ophiolites. It is found that it is not the extension of the Fuchuan ophiolites.