太行山南段邯邢地区叩天井闪长岩成因:来自锆石U-Pb年龄和角闪石地球化学的约束OACHSSCD

The mineralised plutons in the Han-xing region generally exhibit high oxygen fugacity characteristics and are closely related to magnetite formation,but the changes in physicochemical conditions during the deep-shallow evolution of magma and their mineralisation control mechanisms are still not well understood.The Koutianjing region is located in the southern part of the Taihang Mountain tectonic-magmatic activity belt,and its diorite provides an ideal subject for exploring these issues.This study conducted zircon U-Pb dating and hornblende composition analysis on diorite from boreholes in the Koutianjing region,systematically reconstructing its crystallisation temperature,pressure,oxygen fugacity,and formation depth.The results show that the diorite formed in the Early Cretaceous,with a weighted average age of 126.8±7.8 Ma,consistent with the main mineralisation period of the Hanxing region.Hornblende records a two-stage crystallisation process:the first stage formed under high-temperature conditions(866～963℃),medium pressure(203～405 MPa),and high oxygen fugacity(ΔNNO=+1.06～+3.09),at a crystallisation depth of 7.16～14.30 km,as magnesian calcic hornblende crystallised from mantle-derived magma;the second stage formed under comparatively lower temperatures(628～667℃),low pressure(26～33 MPa),at a crystallisation depth of 0.93～1.15 km,as shallow hornblende formed during the evolution of crustal-source magma.Combining the chemical characteristics of hornblende in mineralised plutons in the Hanxing region,it is suggested that the Koutianjing diorite records a multi-stage evolution from"deep mantle-derived high oxygen fugacity magma to shallow crustal-derived evolved magma".