Mesozoic Magmatism And Related Metallogenesis In Northern Taihang Mountains

Mesozoic tectono-magmatism-metallogenic belt in the northern Taihangmountains is located within the North China Craton (shortly NCC), is one of thelarge-scale magmatism in eastern China. The studies on temporal-spatial distributionregularity of batholiths and deposits, source of magma and ore-forming material, willbe significant to provide evidences to reveal the process of igneous evolution anddynamic mechanism. Therefore, this article carried out researches on petrology,geochemisty, isotope geochemistry, diagenetic and metallogenic zircon U-Pbgeochronology, and ore-forming fluid temperature in magmatic intrusions andmineralization of the Mesozoic northern Taihang mountains.Dahenan and Laiyuan complexes are the typical granitoids in northern Taihangmountains and can be divided into three periods (early, middle, late). They aregenetically I-types. The emplacement time of Dahenan and Laiyuan complexes are127Ma～147.4Ma,126.4Ma～146Ma, respectively. The rocks related to skarndeposits in the article belong to the earlier stage of early and late period, andmetallogenic epoch mainly concentrates on140Ma approximately. Skarn Fe depositsformed in an oxidation environment and degree of oxidation gradually reduced. Theore-forming fluids are characterized by high temperature and strong enrichment of Eu,and magnetite formed at high temperature. S isotope compositions indicate that sulfuris from deep crustal or even upper mantle derivation. Pb isotope compositions implythat lead is mainly from lower crust with little upper mantle.Early and middle period rocks, from Dahenan and Laiyuan complexes，have thedepth of magma source over50km, with garnet of residue of magma source. Lateperiod rocks have the depth of magma source40～50km, with plagioclase of residueof magma source. Controlled by the west circum-pacific plate, North China developedtectonic transformation (150Ma～140Ma) and lithosphere large-scale thinning, thenleading the large-scale crust-mantle interaction and the transfer of energy and materialfrom deep earth to shallow. So, the strong magmatism and polymetallic deposits which are dominated by skarn-type and a few porphyry-and hydrothermal vein-typeformed in the northern Taihang mountains.