Tectonic Evolution And Mineral Deposit Distribution Of The Mineralization Belt Of The Lower-middle Yangtze River

The middle-lower Yangtze River area is located in the south of the junction zone,which is formed by the collision between the North China and South China plate. Themiddle-lower Yangtze River area is one of famous copper, iron and polymetallic oremetallogenic belt in China, including a serious of ore concentration area such assoutheast of Hubei, Jiurui, Anqing-Guichi, Tongling, Lucong and Ningwu, the lengthof which is about2000km. The tectonic evolution of metallogenic system, with ahigh prospecting potential, is extremely complicated. The middle-lower YangtzeRiver area is realted to the interaction between two different-generation orogens: theDabie Orogen and the Jiangnan Orogen. The metallogenic belt was reshaped bymulti-stage, multi-directional tectonic events, recording the evolution of the twoancient orogens. The metallogenic belt with a highly complex structural phenomenonis located in the core of the integrated and transformed zone of the Neo-ThetysTectonic Domain and the Paleo-Pacific Tectonic Domain. The records of Mesozoicsedimentary sequence, magmatic-metallogenic framework, tectonic events in themetallogenic belt are a natural platform to study the mentioned-above researchsubjects. Previous long-term research is focused on the igneous and ore depositgeochronology, geochemistry, but quite a few structural factors controlling igneousrocks and ore deposits distribution were mentioned, which failed to clearly recognizethe close relationship among deformation, magmatism and metallogeny. It hasbrought great problems for further predicting and explorating favorable metallogenicbelt and mineral reserves.In this paper, the middle-lower Yangtze River area is divided into the fivetectonic units: the North China Block, the Dabie Orogenic Belt, the Yangtze Block,the Cathaysia Block, the middle-lower Yangtze River Foreland Belt. In early Yanshanian （J₁-J₂）, the middle-lower Yangtze River area develops thrust-and-nappestructure, NNE-and NE-trending in the lower Yangtze area, and nearly E-W-orNWW-trending in the middle Yangtze. Along the Yangtze River the metallogenicbelt formed foreland anti-directed structural system. The south area is named theTongshan-Ruichang-Shitai-Ningguo fold-and-thrust belt, and the northeanBaoKang-WuHan-SuSong-Chaohu fold-and-thrust belt. On the south side of theYangtze River, developed the NW-directed thrusts. The fold styles from the front tothe root are various from chevron anticlines to chevron synclines. The root of thethrust belt is located in the south of the JiangShan-ShaoXing Fracture Zone. TheNW-directed thrusting in the southern may be associated with the high-speedsubduction of the Paleo-Pacific Plate to the Asian Continent, While on the north sideof the Yangtze River, the SE-directed thrusting should be related to the extrusion ofthe Dabie Orogenic Belt. During J₃-K₁, the study area developed two stages ofmagmatic activity: the early stage is high-K calc-alkaline series, and the late belongsto andesitic porphyrite series. During the late-stage, the study area formed a series ofNNE-trending volcanic basins.Based on the thorough research, this paper reveals a series of sinistral strike-slippull-apart basins in J₃-K₁and later in K2, the tectonics of the study area switchedfrom thrustingto strike-slipping faulting-extrusion which was caused by theS-directed and the N-directed indentation of Dabie Orogenic belt Yangtze Blockrespectively, and formed a large number of pull-apart basins and faulted depressionbasins in the Middle-Lower Yangtze region which is related to high-speed obliquesubduction of the Paleo-Pacific Plate in the late Yanshanian. Since145-125Ma, thetwo-stage magmatic activities in the study area were correspond to the developmentof Cu, Au ore deposits and Fe, S ore deposits, respectively. The main controlingfactors of mineralization are strata, rocks and tectonics. The mineralization in studyarea has a close relationship with strike-slip faulting, and the regularities of oredeposits are “NNE-trending zonation distribution and NWW-trending regionaldistribution”. The dynamics of tectonism-magmatism-mineralization is correlated tothe subduction of the Paleo-Pacific Plate, and the processes are subduction-triggered J₁-J₂thrusting, crustal thickening, delamination and mantle upwelling. During J₃-K₁the study area develops high-K calc-alkaline rocks and Cu-type ore deposits at theearly stage of strike-slipping, and at the late-stage andesitic porphyry rocks andFe-type deposits...