Plenty of ultramafic enclaves are included in the Mesozoic high-Mg diorites from the central and eastern parts of the North China block. The geochemical characteristics of the high-Mg diorites were formed through reactions between the ultramafic rocks and low-Mg, felsic magma produced by partial melting of lower crust Residence timescales of the ultramafic rocks in the hot magma, however, are poorly known. In this work, we have investigated the residence timescales of dunites in hot ( -9501) dioritic magmas from the Tietonggou pluton in western Shandong Province and the Han-Xing pluton in Hebei Province, based on numerical modeling of the diffusional Mg-Fe zonings preserved in the dunites. We show that the residence timescales of dunites in the dioritic magmas are 102 ～ 103y. This conclusion is meaningful for understanding the detailed processes of reaction between ultramafic rocks and intermediate-felsic magmas and formation of high-Mg diorites.%我国华北板块中-东部的中生代高镁闪长岩中含有许多超基性岩捕虏体.超基性岩与低镁的中酸性壳源岩浆之间发生反应,形成了高镁闪长岩现有的成分特征.然而,对超基性岩捕虏体在高温岩浆中的存留时间尺度的了解还很少.本文对鲁西铁铜沟和河北邯邢地区高镁闪长岩中纯橄岩捕虏体中保存的Mg-Fe扩散成分环带进行了数值模拟研究,结果表明,纯橄岩在高温( ～ 950℃)闪长质岩浆中存留的时间尺度约为102～103年.这一研究结果有助于我们更细致地认识超基性岩与中酸性岩浆的相互作用以及高镁闪长岩的形成过程.
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