Research On Late Paleozoic-Triassic Tectonic Evolution And Metallogenetic Regularities Of Iron-polymetalic Deposits In The Southwestern Fujian Province

The Southwestern Fujian Province is important part of the Yongmei depression belt, and its geotectonic location belongs to Cathaysia, also a part of the circum Pacific volcanic belt and polymetal metallogenic belt, which has undergone the transformation from Tethys to the circum-Pacific tectonic domain. The basic tectonic framework of"zoning in the E-W direction and blocking in the S-N direction"has been formed during long term geological evolution. At the same time the favorable metallogenic conditions and abundant mineral resources have been brought up in this area which has become the significant ore-concentrating place of iron and polymetal mineral resources in China.The Fujian Province is divided into three three-order tectonic units, i.e. the Wuyi basement complexes, the Southwestern Fujian passive continental margin and epicontinental basin and the Eastern Fujian magmatic arc in this paper. Among them the Southwestern Fujian passive continental margin and epicontinental basin can be further divided into four the forth-order units: Wuping-Taoxi basement complexes, Nankou-Qingliu intracontinental rift, Changting-Shanghang continental slope and Datian-Longyan epicontinental basin. Sedimentary mineralization and tecto-magmatic evolution within this area are controlled by Ninghua-Nanping, Zhenghe-Dapu, Shanghang-Yunxiao, Minjiangkou-Yongding four major deep fault zones. The two of Indosinian and Yanshanian periods of thrust nappe tectonic belts developed in the study area, of which the two of Mingxi - Shanghang and Nanping - Longyan Indosinian NE-trend nappe tectonic belts show thrusting from NW to SE. Yanshanian nappe tectonic belts also can be divided into two types: the eastern thrust nappe belt along Zhenghe-Dapu deep fault zone, and the western Mingxi-Qingliu thrust nappe belt demonstrate thrusting from east to west.Through analysing the late Paleozoic - Triassic sedimentary features, lithofacies palaeogeography and tectonic environment, it is obtained that the study area during late Paleozoic - Triassic is an important part of the E-W Tethyan tectonic domain, suggesting that there exists "the eastern Fujian ancient land " during Late Paleozoic- Triassic, and proposing the Late Paleozoic - Triassic Tethyan tectonic evolution model in the study area, which can be divided into four evolution stages: the formation of crystalline basement, the formation of metamorphic folded basement, the development of epicontinental basin and the active continental margin.By detailed study of the Makeng, TangQuan typical iron ore deposits, it is thought that the Makang iron ore deposit is the sedimentary and reformed deposit. And the Re-Os isochron age of the Makeng associated molybdenite superimposed by hydrothermal solution is 130.5±0.92Ma.By summarizing the regional metallogenic conditions and the temporal and spatial distribution regularities, the regional metallogenic model and iron ore prospecting indicators have been proposed, and two iron metallogenic subzones (four level) have been divided: the Datian-Jiangle contact metasomatic iron metallogenic area and Longyan-Dehua sedimentary-reformed iron metallogenic area, and the Jiangle-Wanan, Xinan in Yongan–Longfengchang in Datian, Yindingge in Datian, Guashan in Zhangping, Yangshan in Dehua, Pantian -Jiandou in Anxi, jiaoshan in Longyan- Daban in Zhangping, Luoyang in Zhangping, Makang in Longyan, Huyang in Shanghang 10 iron ore prospecting areas (the fifth level). Recommendations on the deployment of prospective areas have been put forward.