晚中生代中国东部高原北界探讨  

Discussion of north boundary of the East China Plateau during late Mesozoic Era

作　　者：张旗[1] 金惟俊[1] 王元龙[1] 李承东[2] 贾秀勤[3] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国地质调查局天津地质矿产研究所,天津300170 [3]中国科学院高能物理研究所,北京100039

出　　处：《岩石学报》2007年第4期689-700,共12页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程基金(KZCX 1-07和KZCX2-SW-119)资助的项目

摘　　要：中国东部高原的界线主要是依据埃达克岩的分布确定的。现已知道,高原最北部的中生代埃达克岩主要分布在辽西-冀北-内蒙古南部一带。该区可靠的埃达克岩仅发育在晚侏罗世或早白垩世的早期(如132±5Ma的安家营子花岗岩)。现有资料表明,大致以赤峰-开原断裂为界,埃达克岩分布于其南,其北为非埃达克岩分布区,暗示中国东部高原的北界大体沿赤峰-开原一带分布,代表的是侏罗纪时期的高原边界。辽西义县组地层位于高原范围内,众所周知,义县组第2段(124～127Ma)是热河生物群集中发育的阶段,说明当时的气候温湿、植物繁茂、水草丰盛、地势低洼、湖沼发育,不大可能为动植物贫瘠的高寒山区。义县组火山岩的研究表明,早白垩世(135～120Ma)的义县组主要由玄武岩和赞岐岩(高镁安山岩)组成,并非埃达克岩。因此,至少在127Ma左右,在热河生物群分布的地区,已经不存在高原了,高原的界线南移了,可能移到热河生物群发育区之南的宣化-滦平-锦州一线,其南仍然处于高原环境。高原抬升的直接结果是导致同时代沉积物的缺少,或有一些沉积盆地发育,但是厚度很薄。在中-晚侏罗世时,高原上的沉积盆地很少,且缺失上白垩统地层,总体上反映高原处于抬升状态。高原北缘和西北缘早白垩世冰筏和冰川泥石流沉积的出现,暗示高原的北缘可能具有相当的高度,可能类似现今的喜马拉雅山。该区中生代构造特征表明,该区侏罗纪和早白垩世的构造特点有着巨大的差异:侏罗纪,尤其是晚侏罗世末期以南北向的挤压构造为主,而早白垩世中期以后演变为以伸展构造为特征,古地理古环境明显改变。研究表明,中国东部中生代埃达克岩形成的时限大致限定了高原的起始和消亡时间。据最近几年发表的资料,埃达克岩的时代大体限定在170～120Ma之间,表明中国东部高原在170Ma之�The boundary of the East China Plateau （ECP） is mainly definited on the distribution of adakites. It has already known that the northernmost adakites of the plateau during the Mesozoic Era were distributed in the western Liaoning Province, northern Hebei Province and southern Inner Mongolia. The reliable adakites were dated between the early of Early Cretaceous and Late Jurassic period （such as Anjiayingzi granite in 132 ±5Ma）. The present data show the adakites are roughly separated from non adakite by the Chifeng- Kaiyuan fault, is distributed on the south of. These imply that the northern boundary of the ECP is along the Chifeng-Kaiyuan zone and it represents the plateau border during Jurassic Period. The Yixian Formation in the western Liaoning lies within the plateau. As is known that the second section of Yixian Formation （ 124 - 127Ma） is the same as the stage of the Jehol Biota development, it means the climate at that time is warm and humid, luxuriant plant, the sumptuous pasture, low elevation, lacustrine lake. So it was unlikely belong to the barren and cold mountain, where is lack of animals and plants. The volcanic rock research of Yixian Formation shows that Yixian Formation during the Early Cretaceous（ 135 - 120Ma ） is mainly composed by basalt and sanukite （high magnesium andesite ） which are non adakite. So at least about 127Ma ago there is not plateau distributed in the Jehol Biota areas, the plateau boundary shift southward. It may be along Xuanhua-Luanping-Jinzhou zone to the south of the Jehol Biota district. No contemporary sediment, or the very thin sediment in the basin is directly result from plateau uplift. There was no basin in plateau during the middle-late Jurassic period, which is lack of Cretaceous stratum, implies that the plateau is generally on the uplifting stage. The ice raft and the glacier mud rock flow deposited along the northern and northwest edge of the plateau during early Cretaceous, implies that the northern edge of the plateau may be of the suitab

关 键 词：中国东部高原 中生代 北界 辽西 义县组 热河生物群 埃达克岩 赞岐岩 

分 类 号：P588.122[天文地球—岩石学]