【作者】 孙延贵；

【导师】 张国伟；

【作者基本信息】 西北大学 ， 构造地质学， 2004， 博士

【摘要】 秦岭、昆仑造山带是中央造山系的主要组成部分，东西连接构成一条东西横贯我国大陆中部的巨型造山带，它不论是对中国大陆构造基本格局的形成还是对现今中国南北近地表系统的差异均具有十分重要的影响。但由于二者在青藏高原东北部的共和地区出现了构造的不连续现象，即在西秦岭与东昆仑之间出现了所谓“共和缺口”，即出现了两造山带间，或者说中央造山系中自晚古生代，尤其自中新生代早期以来的构造分割，或者说构造变换，造成不同研究者对它们之间的构造关系有着不同的认识，甚至认为西秦岭与东昆仑本来就是不同的造山带，因此“共和缺口”的性质、形成、演化及其成因成为许多地质学家孜孜探求的答案。为此，在前人研究基础上，选择这一重要而又存争议的科学问题进行探索，选择西起青海天峻—乌兰—都兰—玛多一线以东，向东至甘青交界，南北夹持于阿尼玛卿山与青海湖南山之间的广大区域为研究区，在新的学术思路，板块构造与大陆动力学的探索为探寻思想，在充分利用已有调查研究成果的基础上，重点对一些关键地段进行了新的野外调研，从实际出发，以新的地学理论为指导，多学科结合，从西秦岭与东昆仑两条造山带衔接区(共和缺口)的物质组成、结构构造及其演化过程等方面探索它们的衔接转换关系以及动力学特征。本文首先在总结分析目前有关西秦岭—东昆仑衔接区以及邻区秦、祁、昆、巴颜喀拉等造山带研究现状及其存在主要问题的基础上，对与西秦岭—东昆仑衔接转换紧密相关的各造山带基本特征进行了简要性的讨论，重点首先对衔接区域现今基本组成、结构重新研究认识，而后筛分追塑恢复重建晚古生代至中生代早期的组成与结构构造，包括区域的伸展构造、俯冲碰撞构造、碰撞造山构造以及后期复合迭加构造进行了大量的调查与研究，并对有关的深部地球物理探测成果进行了综合分析，进行了地质、地球化学与地球物理多学科的综合研究，最后在上述实际调查和综合研究基础上探讨与建立了西秦岭—东昆仑构造衔接转换关系及其构造动力学过程，并在以下方面取得新的进展和认识。 1．有争议的“共和缺口”，研究表明可能是深部地质背景下的三联点构造发生发展演化的结果。以玛积雪山南可能代表古幔柱—热点产物的以大量碱性玄武岩出露为主要特征的蛇绿混杂岩出露位置为原“三联点”，东昆南蛇绿构造混杂岩带、阿尼玛卿—文县—勉略蛇绿构造混杂岩带与苦海—赛什塘蛇绿构造混杂岩带在时、空上构成秦昆三向联结构造，其中鄂拉山与共和盆地先期为伸向秦岭微地块中的未及充分扩张发育的夭折消亡的一臂。该构造系统应是秦、祁、昆、巴颜喀拉诸造山带在时、空地质演化中有机结合的关键构造。三联点构造中的共和夭折的坳拉谷是分害」并又使西秦岭与东昆仑造山带和柴达木地块(同属柴达木一秦岭微板块)发生转换衔接的主要构造形式。 2.通过对西秦岭一东昆仑衔接区的构造解析和不同期次构造的筛分可将衔接区的构造变形划分为伸展期、俯冲碰撞期、碰撞造山期、主造山期后的改造期等四个主期变形构造。不同期次的变形构造具有不同的构造样式，但它们具有统一动力学背景，并与衔接区区域在不同构造演化阶段所处的动力学环境相适应。 3.通过对西秦岭与东昆仑及其衔接区地层沉积特征、古生物面貌等所反映出的构造一岩相古地理对比研究认为，衔接区曾经历过发育于原华南板块北部被动陆缘上的被动型裂谷、由慢柱构造引发洋脊扩张而造成的主动型裂谷以及陆一陆碰撞后形成的前陆盆地等不同盆地动力学类型的发展演化过程。 4.通过对与共和坳拉谷演化不同阶段中所出现的重要构造事件相伴生的岩浆活动、变质作用同位素年代学研究，获得了共和坳拉谷初始伸展(与共和坳拉谷初始伸展相伴生的拉龙洼基性岩墙群辉石4伙r一39A;的高温坪393.5Ma年龄及其斜长石40Ar一39A:的高温坪361.SMa年龄)、俯冲碰撞(苦海一玛温根山岛弧或陆缘火山弧英安岩错石U一Pb年龄:263.9Ma;拉龙洼基性岩墙群变质年龄:262Ma和261 .SMa)、碰撞造山(鄂拉山碰撞花岗岩同位素年龄:220一200Ma)以及造山后造山带伸展垮塌(伸展垮塌期形成的满丈岗基性岩墙群40A卜39A:的195.7Ma年龄以及属A型花岗岩组合的纳让地区石英正长岩单颗粒错石U一Pb的199.6Ma年龄)等一系列重要构造事件发生的同位素年代学证据。 5.利用岩石学、岩石化学、同位素地球化学以及地球物理学对鄂拉山花岗岩浆一火山活动带、青海湖南山花岗岩浆带以及多福屯火山活动带等三条构造岩浆带进行了综合研究，证明它们的发生与形成均反映是西秦岭一东昆仑衔接过程晚期陆内构造作用及其深部的动力学特点。 6.多方法地球物理探测成果所揭示的深部地质背景特征显示，柴达木一西秦岭总体是一个被夹持在华北与华南板块间的向北陡倾的板状构造体，北边界的柴北缘一青海湖南山一天水一武山古缝合带和南边界的东昆南一阿尼玛卿古缝合带均属岩石圈性质的构造界面。柴达木与西秦岭之间的苦海一赛什塘构造带在深部同样有着明显的反映，即柴达木与西秦岭之间沿该构造带形成一个约SKm的莫霍面落差，它不仅证实原共和坳拉谷的存在，而且说明西秦岭向柴达木地更多还原

【Abstract】 As major parts of the central orogenic system, the Qinling and Kunlun orogens constitute a giant orogenic belt that stretches from east to west in central China. The orogenic belt has played an important role in the formation of China’s continental tectonic framework and the differentiation of today’s China environment on both sides of the belt.However, due to structure discontinuity in the Gonghe area in the northeast Qinghai-Tibetan plateau, that is the so-called "Gonghe Gap" between the west Qinling and east Kunlun orogens, some disagreements on the tectonic relationship of the two orogens have long existed among geologists. Some researchers even doubt if the two belong to the same orogenic belt. Thus, the origin of the Gonghe Gap has become a key issue on China’s continental tectonics.In pursuit of the origin of the Gonghe Gap, the present study has selected an area between the border of Gansu and Qinghai provinces in east and the Tianjun-Wulan-Dulan-Maduo counties in Qinghai province in west, and the A’nyemaqen mountain and the Qinghaihunanshan mountain in south and north respectively as a study focus. Based on previous investigation and researches, the study has carried out some detailed field work in key portions in the study area, aiming at exploring conjugate and transfer relations for the west Qinling and east Kunlun orogens, and their dynamic characteristics according to their composition, structures and evolution processes in the conjoining area between the west Qinling and east Kunlun orogens.Having summarized and analyzed present major issues of the west Qinling-east Kunlun and the neighboring east Qinling, Qilian, Kunlun and Bayankala orogenic belts, the study briefly discusses essential features of the above orogenic belts closely related to the conjugate and transfer relationship of the west Qinling-east Kunlun orogens and put stress on all deformation structures occurred during extensional period, subduction-collisonal orogeny, collisional orogeny and post orogeny. Also, this study comprehensively analyzes geophysical determination results from depth and geology and geochemistry as well as tectonic settings of ophiolite, basic dyke swarm, collision-type granitoids formed in the conjoining area. Furthermore, petrofacies-paleogeography of the conjoining area is discussed in light of stratigraphy and paleontology. Finally, a 4-D dynamic evolution model of the west Qinling-east Kunlun conjugate and transfer (Gonghe aulacogen) has been established on the basis of the above work.1. The ophilite melange zone in southern east Kunlun, A’nyemaqen-Wenxian-Mianlue ophilite melange zone and Kuhai-Shaishitang ophilite melange zone spatially and temporally form the typical Qinling-Kunlun triple conjunction tectonics. Characterized by the ophiolite melange with major component of alklibasalts which represent apaleo-mantle and hot spot product, the south of the Majixueshan probably is the site of the triple junction. The Qinling-Kunlun triple conjunction tectonics is considered to be the core structure for connecting Qinling, Qilian, Kunlun and Bayankala orogenic belts together in terms of time and space, while the Gonghe aulacogen in the triple conjunction tectonics probably represents the main tectonic form that separates the west Qinling from the Qaidam massif but does not affect their unification (both belong to the Qaidam-Qinling micro-plate) and through that the west Qinling and east Kunlun were conjugated and transferred.2. Structural deformation in the conjunction area can be recognized in four main stages: extension, subduction-collision, collisional orogeny, reworking stage of post orogeny. Deformation in the different stages possesses distinctive structure patterns that reflect corresponding tectonic settings.3. By tectono-petrofacies and paleographical comparison of the west Qinling orogen and the east Kunlun orogen with the conjunction area, it can be inferred that the area has experienced passive rifting, active rifting and foreland basin evolution processes of different basin dynam更多还原