晚侏罗世承德盆地砾岩碎屑源区分析及构造意义  

Provenance analysis of the conglomerate clastic compositions from the Late Jurassic Chengde basin and its tectonic significance

作　　者：和政军[1] 牛宝贵[1] 张新元[2] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质调查局地质发展中心,北京100083

出　　处：《岩石学报》2007年第3期655-666,共12页Acta Petrologica Sinica

基　　金：国家自然科学重点基金项目(40132020);中国地质调查局项目(1212010511502)资助成果

摘　　要：河北承德及寿王坟盆地在晚侏罗世土城子期堆积了大量的粗碎屑沉积。砾石成分统计结果显示,承德-寿王坟盆地充填的土城子组碎屑母岩组合主要有三种,其中火山岩、花岗质岩石和变质岩组合在承德盆地占绝时优势,反映了当时盆地以北的"内蒙地轴"为主要的蚀源区。向北逆冲的双庙断裂将承德盆地分成南北两个部分,断裂两侧的砾石成分组合基本相同,显示出碎屑物质共同来源于北部,同时也暗示了该断裂在土城子期可能没有强烈的活动(强烈活动期可能在土城子组之后?)。分析表明,承德盆地南部的不对称向斜构造两侧砾石成分截然不同,说明该向斜构造控制了碎屑分布,是同沉积期形成的。该盆地南侧的碎屑供应量远远小于北侧,反映了控制盆地南缘发育的向北逆冲的灰窑断层可能是一条次要的同沉积断裂。在晚侏罗世整体向南推进的逆冲断裂系统中,灰窑断裂和双庙断裂应属于背向逆冲断层。承德盆地中大量的粗碎屑堆积与同期冲断带的耦合关系分析,指示了这一时期盆地北侧存在强烈的逆冲断裂活动。作为主要物源区,北部的"内蒙地轴"在晚侏罗世发生了强烈的隆升-剥蚀作用,推测当时在地貌上可能存在近E—W走向的古山系(或古高原?)。A mass of coarse clastics were accumulated in the Chengde and Shouwangfen Basins of Hebei Province during the Late Jurassic. Clasts of conglomerates from the Late Jurassic Tuchengzi Formation have been categorized as three assemblages in the Chengde and Shouwangfen basins, which include crystalline basement and volcanic rocks, carbonates and volcanic rocks, and volcanic rocks and carbonates. The crystalline basement and volcanic rocks are predominant in coarse clastics among the three assemblages, indicating that the part of the ＂Inner Mongolia Axis＂ on the north of the Chengde basin was the main provenance throughout the Late Jurassic. Conglomerate clastic compositions on the both sides of the Shuangmiao fault, thrusting northward and cutting the Chengde basin to two parts, are basically consistent. It reflects that clastic compositions on the both sides of the thrust fault together derived from the north provenance. This evidence implies that the fault was weakly active in the most of the Tuchengzi time （ probably intensive activity in post-Tuchengzi time？）. Our analysis shows that conglomerate clastic composition on both the limbs of the asymmetrical syncline in the south of the Chengde basin is completely different, which reflects the clastic distribution was controlled by the syncline as a syn-depositional structure. Clastic supplies （ dolomites and volcanic rocks） from the south of the basin were markedly less than those of the north, revealing that the Huiyao thrust fault was a secondary order fault, which controlled the development of the south limb of the Chengde syncline. The both faults, the Huiyao and Shuangmiao faults, as back-thrust faults, probably played a role of accommodation fault due to propagation of main thrust system southward-directed in the Tuchengzi time. According to coupling between basin filling and contemporary thrust belt, accumulations of a mass of coarse clastics from thrust front possibly implies that existed strong thrusting on the north of the Chengde basin during

关 键 词：承德盆地 晚侏罗世 砾岩碎屑 物源区分析 

分 类 号：P588.21[天文地球—岩石学] P542.2[天文地球—地质学]