MAIN FEATURES OF THE SHILU DUCTILE SHEAR ZONE IN HAINAN ISLAND AND METALLOGENY OF THE“BEIYI-TYPE” IRON ORE DEPOSIT
Hou Wei1, Xiao Yong2, Chen Fansheng3
1. General Office, Chinese Academy of Sciences, Beijing 100684; 2. Bureau of Geology and Exploration of Hainan Province, Haikou 570206; 3. Quality Superintendence Station for Architecture Engineering of Haikou City, Hainan Province, Haikou 570013
The tectonic evolution of Hainan Island experienced four main stages:the pre-geosynclinal stage in Archean and Paleoproterozoic,the geosynclinal stage since Mesoproterozoic,the plateform one during Late Paleozoic and the diwa(geodepression) stage during Meso-Cenozoic.The Shilu Group in age of Neoproterozoic was a geosynclinal record,with the original and lower-grade iron ore formed.The Shilu ductile shear zone occurred in the earliest Cambrian,and in the deformational process the Beiyi-type iron-rich ore deposit created.The paper introduced megascopic and microscopic structural features of the Shilu ductile shear zone and the pressure solution,plastic flow and synkinematic geochemical characteristics in the process of mylonitization in details.In the light of the theory of structure controlling diagenesis and ore-forming,the metallogeny of the Shilu iron ore deposit was analyzed.The Beiyi-Jixinhe and the Fengshuxia-Zhengmei mylonitic belts played a key role in formation and distribution of the ore deposit.Based on the recent study,a concept of “Beiyi-type” ore deposit was represented,its main metallogenetic laws were summarized,and the prospecting target regions discussed.Furthermore,the ore-search in the Precambrian basement rocks and in the deeper crust of Hainan Island were explored.