海南东南部韧性剪切变形带锆石U-Pb年代学特征及其地质意义

海南东南部韧性剪切变形带断续出露于芒三水库—吊罗山林场—兴隆—线,走向北东,岩石有构造片麻岩和糜棱岩化花岗岩,主要矿物组成为长石、石英、黑云母.岩石发育“S-C”组构、“δ”型旋转碎斑系、云母鱼等变形组构,指示具有右行剪切活动的特点.根据矿物组成及变形特征,认为其变形环境相当于低角闪岩相,属于沿剪切带侵位并发生同步变形的产物.在芒三水库、吊罗山林场两地测得岩石锆石激光ICP-MS法年龄分别为284.3±1.3 Ma、265.9±1.3 Ma,属二叠纪形成.剪切变形带的发现及其年代学的厘定,对深入研究海南岛构造-岩浆作用具有重要的地质意义.

ACORITE U-Pb CHRONOLOGY CHARACTERISTICS AND ITS GEOLOGICAL SIGNIFICANCE OF DUCTILE SHEAR DEFORMABLE BELT IN SOUTHEASTERN HAINAN ISLAND, CHINA

The ductile shear belt exposures in Mangsan Reservoir-Diaoluoshan Tree Farm-Xinglong area successively with its strike being north-east. The lithology is tectonic gneiss and granite of mylonitization, and main minerals are composed of feldspar, quartz and biotite. The rock develops as ＂S-C＂ fabric, ＂＂ style gyral porphyroclast system, mica fish etc. The tectonic fabric indicates right handed shearing movement. According to mineral component and deforming feature, the deforming environment should be low amphibolite facies, which belongs to the product emplacing across the shear zone and transforming synchronously. This time we got 284.3 ± 1.3 Ma and 265.9 ± 1.3 Ma by laser ICP-MS for zircons from Mangsan Reservoir and Diaoluoshan Tree Farm. The founding of ductile shear belt and its geologic age plays an important role in the intensive study of construction-magma function of Hainan Island.