The Upper Cretaceous Sedimentary Characteristics And Provenance Analysis Of Hekou Formation In Fuzhou-chongren Basin,jiangxi

Gan-hang tectonic belt is located on the southeastern margin of the East Asiancontinent, across two first-order tectonic units of the Yangtze block and Cathaysia block.Mesozoic volcanic rocks and the red clastic rocks are common in the basin, the basinoutputs uranium and polymetallic ore. Fuzhou-Chongren basin Province is situated at thewestern section of Gan-hang tectonic belt, The Cretaceous continental red beds wasdeveloped in the basin, Xiangshan uranium ore-field on the west side of the basin is animportant volcanic-type uranium producing area in China.Based on measurement and drawing of the outcrop sections, field work of thestatistics for pebbles, Identification of rock thin sections, the geochemical analysis resultsof major elements,trace elements and rare earth elements, the Author conducted acomprehensive study of siliciclastic rocks of Cretaceous Hekou Formation inFuzhou-Chongren basin, the results suggested that:Fuzhou-Chongren basin is a red continental basin that developed in tectonic setting ofcrustal extension and fault depression, Mesozoic cretaceous strata was found in the basin.The strata is mainly composed of a purple red, brick red or light red rough clastic rockseries of continental，and the composition of gravels of the clastic rock series is complex.The sorting of the gravels is poor in general, the gravels have the characteristics of low tomedium maturity, multi-provenance, short-distance carrying and rapid accumulation. Thesedimentary facies of Hekou period is alluvial fans in general with accidental fluvialsedimentary environment. The Provenance was mainly from the northeastern, northern,northwestern and southeastern of the basin. The Mesoproterozoic and Neoproterozoicstratas of low-grade metamorphic rocks series and Yanshanian magmatic rocks on bothsides of the basin provided abundant clastics for the rapid accumulation of the red basin.The geochemical features of major elements of Hekou Formation clastic rock is richin SiO2, poor in Al2O3、Fe2O3T、MgO; the abundances of several trace elements such assiderophile elements Ni, Co, lithophile elements Sc, V, Sr, Th, chalcophile elements Zn, Cuis below the crustal abundance values, and the abundances of siderophile elements Cr,lithophile elements Ba is beyond the crustal abundance values; Rare earth elements has thecharacteristics of relative enrichment of light REE,relative loss of heavy REE and negativeanomaly of Eu, Ce. The tectonic setting of the provenance of Fuzhou-Chongren basin is relativelycomplex. The provenance is mainly situated between active continental margin and passivecontinental margins. Parent rocks of clastic sediments in the basin were mostly Granites,metamorphic rocks and small amounts of sedimentary rocks. Sedimentary environment ofthe basin is fresh water phase of oxidative sedimentary environment，the evolution of thesedimentary progress was complex and mainly circulation of sustainable weathering andredeposition.