区域变质作用对北京房山侵入体冷却影响的数值模拟

通过传热数值模拟分析了区域变质作用对北京西山房山侵入体冷却的影响。结果表明，房山侵入体必须处在周围长期高温下才能维持其中央从角闪石Ｋ Ａｒ封闭温度到榍石有效径迹保留温度长达１５１Ｍａ的缓慢冷却。侵入体冷却自早到晚分为以侵入体高温为主导的、以区域变质衰减为主导的和抬升剥蚀３个冷却阶段。区域变质发生在中、晚侏罗世，持续到早白垩世晚期。

IMPACT OF REGIONAL METAMORPHISM ON THE COOLING OF THE FANGSHAN INTRUSIVE BODY, WESTERN BEIJING:NUMERICAL SIMULATION

By means of numerical simulation, the impact of regional metamorphism on the cooling of the Fangshan intrusive body in Western Hill of Beijing is studied. The result indicates that regional and secular high temperature in the country rock should be required to sustain a cooling of ca. 15 1Ma in the central part of the Fangshan intrusive body from K Ar closed temperature in hornblende to effective fission track retention temperature in sphene. From early to late the cooling history of the body can be divided into three stages: dominative high temperature of magma, dominative regional metamorphism decreasing and erosion. In the area regional metamorphism took place in the Middle and Late Jurassic and most probably lasted till the end of the Early Cretaceous, about (114 4±7 5)Ma.