秦岭-桐柏-大别造山带深部构造及其与南北两侧陆块关系之探讨

DISCUSSION ON THE DEEP-SEATED STRUCTURES OF THE QINLING-TONGBAI-DABIESHAN OROGENIC BELT AND ITS RELATIONS WITH THE LANDMASSES ON ITS SOUTH AND NORTH SIDES

秦岭—桐柏—大别 ,向西乃至昆仑山、祁连山绵延 1 0 0 0多千米 ,属统一的而又包含多期不同动力学机制与成因的多种构造叠加组合。通过对数条重力、航磁、地震测深、磁大地电流剖面等资料解释 ,认为华北陆块、秦岭 (包括桐柏—大别 )、扬子陆块之地壳均为上、中、下三层结构 ,华北陆块下部以高角度向南向秦岭俯冲 ,上部则向秦岭仰冲。扬子陆块总体向北向秦岭低角度俯冲 ,扬子陆块多呈楔形镶入秦岭地壳中部 ,使秦岭带南侧呈向南开口的“锷鱼咀”式构造特点 ,上、下部为秦岭上、下地壳 ,而中部则为扬子陆块物质成份。秦岭分北秦岭、中秦岭、南秦岭。北秦岭为一复杂构造带 ,形成向北反转的叠瓦状逆冲推覆构造。南秦岭自北向南产生低角度叠瓦状逆冲断裂。近南北向通渭—武都、南阳—襄樊两条深断裂带将秦岭分成了西秦岭、东秦岭。

Mountains from Qinling Tongbai Dabieshan to Kunlunshan and Qilianshan to westward have a length over 1,000 km. They are an integrated multiple tectonic superimposed group containing multiperiodic different dynamics and genesis. Data interpretation of several profiles by gravimetry, airborne electromagnetics, seismic sounding and geomagnetic current has indicated that the crust in the North China landmass, Qinling (including Tongbai Dabieshan) and the Yangtze landmass can be divided into triple layered structures of upper, middle and lower parts. The lower part of the North China landmass is underthrust to Qinling at high angle souththward and the upper part is of obduction to Qinling. The Yangtze landmass in general is underthruct to Qinling at low angle northward. And it is common that the Yangtze landmass embedded in the central part of Qinling at wedge form, making the southern part of Qinling with a structural pattern of 'crocodile mouth' opening to the south and the upper and lower parts are the upper and lower crusts of Qinling, and the middle part is composed of the materials of the Yangtze landmass. Qinling is divided into three parts with the north, middle and south. The north Qinling is a complicated structural zone, forming an imbricated thrust napped structure overturning northward. The south Qinling has formed an imbricated thrust fault at low angle from the north to the south. Two deep seated faults F 31 and F 32 in the N S direction divided Qinling Mountain into three portions of the west Qinling, the east Qinling and the Tongbaishan Dabieshan.