华北早白垩世末岩石圈局部被扰动的时空证据  

Temporal and spatial evidences for Early Cretaceous disturbance of the lithosphere beneath North China.

作　　者：邵济安[1] 路凤香[2] 张履桥 施光海[4] 

机构地区：[1]北京大学地球与空间科学学院,北京100871 [2]中国地质大学地球科学学院,武汉430074 [3]内蒙古地质研究所,呼和浩特010020 [4]中国地质大学,北京100083

出　　处：《岩石学报》2006年第2期277-284,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金(40372107)研究成果;中国科学院矿产资源研究重点实验室资助

摘　　要：对比研究了辽西阜新碱锅和内蒙古平庄含地幔捕虏体的阜新组玄武岩与碱锅义县组的安山岩,并结合前人的同位素年代学研究,确认在早白垩世117～106 Ma期间,该区火山岩岩浆来源从富集的岩石圈地幔转变成亏损的软流圈地幔,即岩浆作用从以壳幔相互作用为主转化成软流圈的底辟体上升。将岩浆来源的巨大变化与前人关于古地磁和白垩纪超静磁带的研完成果以及研究区脊椎动物群集群死亡事件联系起来,认为这是一次重要的岩石圈圈层结构被扰动的事件。通过区域对比,发现阜新、平庄岩浆源区从富集地幔向亏损地幔转化的事件同样存在于山东沂水以及松辽盆地,而且岩浆来源转化的时间大体一致,均发生在100～80Ma前后。根据前人提供的小比例尺的三维面波速度结构,推断中国东部软流圈物质沿着构造薄弱带上涌,使岩石圈发生局部扰动的起始时间可能是晚中生代100Ma,由于各地构造差异它们可以表现为若干软流圈上涌的底辟体。A comparative study between mantle peridotitic xenoliths-bearing basahs of the Fuxin Formation from Fuxin Jianguo, Western Liaoning Province and Pingzhuang, Inner Mongolia and andesites of the Yixian Formation from Fuxin Jianguo has been carried out in this paper. Combined with geochronological data reported in previous works, we identified that the magma sources of volcanic rocks in the region changed from the enriched lithospheric mantle to the depleted asthenospheric origin in the Early Cretaceuos （117-106 Ma） , i.e. magmatism shifted from the crust-mantle interaction-dominated to the upwelling of the asthenosphere. Such a significant change, which could be linked with paleomagnetism and Cretaceous normal superchron （ CNS ） as well as with the vertebrate mass mortality events in this region, may represent an important disturbance of the lithosphere struucture. Regionally geological comparison suggests that the magma source conversion from an enriched mantle into a depleted mantle occurred in Fuxin and Pingzhuang regions still existed in Yishui, Shandong Province and Song-Liao basin and all these events happened at around same time period （ 100 - 80 Ma）. If the small-scale 3-D S wave velocity structure of this area is taken into account, it can be deduced that the upwelling of the asthenospheric materials along the tectonic weak belt in East China has formed since 100 Ma in Late Mesozoic and it may appear as a few upwelling diapirs of asthenosphere as a result of structural contract.

关 键 词：华北 岩石圈 软流圈 亏损地幔 岩浆源 

分 类 号：P588.145[天文地球—岩石学] P597.3[天文地球—地质学]