【作者】 杨兴科；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 矿产普查与勘探， 2003， 博士

【摘要】 本文以羌塘盆地热力构造作用综合研究为主线，系统总结了该区研究程度不高的热力作用，强调热力作用在青藏高原隆升和盆地演化过程中的重要作用，这一研究思路对该盆地有一较全面的深化和提高。 在地幔柱和热力构造研究进展总结的基础上，对盆地热力构造进行了分类。依据地貌形态分为三类：正向穹窿型、负向塌陷型、边隆核陷型：依据岩浆-热力作用影响的深浅程度或深度分为五类：(古)地热异常群集区、表浅层火山喷发-热液活动与浅成侵入型、热力背斜(热穹窿)、中深层侵入型、深部地幔(地壳)热柱型；提出了热力构造作用空间分布的理想模式，将洋陆系统、盆山作用、浅表与中深部壳幔作用、壳幔混合、垂向热力作用(拆沉)等纳入一个整体统一的热力作用系统中，为盆地动力学研究打开了一个新窗口；研讨了热力构造研究方法。在前人研究基础上，采用地质-地球物理综合研究和三维技术，编制了西、中、东部三条地学综合剖面，研究解释了盆地浅、中、深部不同层次的结构构造样式，得出盆地地壳结构不均一性规律。这种不均一表现为南北分区带、东西分块段、垂向分圈层。建立了该盆地西、中、东三个不同区块典型的盆地地壳结构图。 对盆地深部存在的垂向极低阻异常柱区和壳内电阻率值＜40Ω·m的区带与深部热力作用活动相联系，类似于地幔(地壳)亚热柱。壳内低阻层有三种存在方式，顶界面起伏较大，横向不均一。盆地不同区块热结构不同，为冷、热壳相间，地壳表现为热、轻、软、流、厚壳，地幔表现为冷、重、硬、多相、深幔的特点。 西部隆起区查桑段特殊的航磁、重力和MT显示其由2-3个近东西向大型南倾构造块体叠覆而成，受班公湖-丁青有限洋关闭和相邻地块进一步汇聚形成。 从区域航磁、向上延拓、地震低速层、花岗岩熔融(退磁)实验、新生代火山岩的分布、地震、温泉、地貌等发现，盆地中东部存在一北北东向航磁负异常带，既显示出东西分块，也与北羌塘深部热力作用强烈活动、发育“壳幔混合层”有联系。 总体认为盆地深部热力作用活跃、岩浆活动频繁、热力构造类型多样。 对盆地热力构造的剖析主要侧重在几个有代表性的不同范例上。(1)雀莫错塌陷型热力构造的剖析。侏罗系各组发育，有雀莫错期和雪山期两个沉降堆积中心。前期存在热力-岩浆活动，中侏罗世前为一古隆起，早期深部热力-岩浆作用上拱、喷溢，表浅层隆升剥蚀，晚期深部热力衰减冷却，表浅层塌陷沉降。重磁异常确定的环状火山机构和MT显示深部低阻异常均与热力塌陷范围相当。 (2)确旦错热点的发现。MT显示有一约百余km的特低值电阻率分布区，壳内低阻层已上升到距地表仅约10-15km处。上第三系康托组仍具有较高的Ro值。原生包裹体和次生包裹体均一温度均较高，显示出较高的异常热演化。有28～20 Ma之间的富碱高钾火山岩，为板内裂陷产物。在约28 Ma曾发生过深部岩浆热力上升及火山喷发事件，出现壳幔混合层和部分熔融及快速上涌喷发。火山岩源区应是富集EMII型地幔部分熔融的产物，是加厚的陆壳基底脱水熔融形成的。该热点深部向西位移了约100 km或北羌塘上部向东南移动了约100 km，与高原物质东南逃逸方向一致。 (3)达卓玛热力复背斜由主背斜和多个次级褶皱组成。卫星影像图呈眼球状。中生代地杨兴科:西北大学博士学位论文一一藏北羌塘盆地热力构造作用特征及其演化层热演化程度高。单个褶皱走向复杂多变，翼部摺皱紧密，顶部有更新地层沉积，变形影响到深部超过IOkm，有明显的深部背景，与挤压背斜成因有别。 地震剖面的时间一速度结构明显低于其北相邻地区，MT剖面显示地下6Okm内存在一明显的低阻异常区。深部热力作用活跃，为一个由深部热力一岩浆作用形成的中深层侵入型热力构造，形态上属热力弯窿型，地貌上为边隆核陷型。 班一丁有限洋关闭和相邻两地块拼接碰撞，在早白至世早期87Ma，使南羌塘深部岩浆一热力作用上拱，地壳中浅层发生隆升，形成达卓玛复背斜。其经历了深部热力衰减、岩浆冷却，表浅层发生不均一塌陷沉降。 (4)格拉丹冬、普若岗日等高山区对应布格异常低值，76%反映正相关。重力异常随深度呈现明显的递减关系，说明深部没有古老的基底高密度物质，仅有火成岩体，更深部物质密度更低。格拉丹东明显的重、磁异常显示在IOkm下有高密度异常体，电阻率中等，无磁性。其下为一火成岩体隆起带，之下有更深部的热力作用区。普若岗日重力低、航磁延深不大，深部高阻，两侧低阻。低阻层深埋下陷区显示深部热力作用方式复杂。目前格拉丹东和普若岗日为冷壳，祖尔肯乌拉山以南和确旦错一带为热壳。 (5)向阳湖西南区热弯隆背斜属于一个与火成岩侵入体有关的弯窿状背斜。核部出露早白至世末次火山相流纹斑岩，翼部侏罗系地层呈同心园状。 对盆地岩浆活动特征的系统分析发现，北羌塘火山岩分区分段和继承性、多期性明显，分布广、规模大、北东部火山机构集中，深部热力作用显著。从新第三纪开始，火山活动随时间向北迁移。盆地侵入岩活动不强，晚燕山期一喜马拉雅期盆内侵入岩不发育，仅在格拉丹东一带?更多还原

【Abstract】 This paper based on the comprehensive study the thermal structure of Qiangtang Basin; systematic summarized the thermal structure, which studied in a lower degree in this area. The paper also emphasised the pivotal function of the thermal structure rising and evolution of the basin of Qinghai-Tibet plateau; this method improved and raised the study in the Qiangtang Basin.Based on the summarize study of mantle plume and thermal structure, the paper divided the thermal structure into several pieces. By physiognomy feature, it could be divided into three types of thermal structure: positive dome model, negative collapse model and border dome core collapse model. Based on the depth degree or magma-thermal influenced, it could be divided into five types of thermal structure: (ancient) geothermal anomaly focus region model, superficial volcano eruption hydro-thermalism and hypabyssal intrusive model, thermal anticline (thermal dome) model, mid-deep intrusive model, deep mantle (crust) thermal plume model; and put forward a perfect model of the thermal structure. There are many interaction system could be induced into a systematic thermal interaction, include: Ocean-continent system, basin-mountain interaction, superficial and mid-deep crust-mantle interaction, crust-mantle commingle interaction, vertical thermal interaction (delamination) etc.. All these work make a new way for the study of basin dynamics, discussed the research method of the thermal structure. Based on predecessors research by geological-geophysical synthesized studying and three-dimensional technique, draw up west, middle and east three composite profiles, explanation of the structure model in different level including surface, middle and deep of the basin, finally concluded in homogeneity of the basin is show by belting in south-north trend, block-faulting in east-west trend and vertical sphere-laying. Set up a typical basin crust frame chart of west, middle and east sector individually.For column zone where vertical quite low resistance anomaly exists in deep basin, zone where specific resistance is less than 40 m in shell, they are related to heat power action in deep place which is resemble to mantle (crust) sub plume. The layer of low-resistance in the crust has three existence manners. The summit interface fluctuates a lot and it is not uniform in the cross direction. Different zone block in the basin has different construction. Cold and heat shells are at intervals. Crust behaves as hot, light, flowing and thicker, however, mantle behaves as cold, weight, and harder, multi-phase and deep mantle.The special aerial magnetism, gravity and MT at Chasang Segment in the western uplifting district show that it is superposed by two or three large-scale south dipping structural block with east-west strike. The closure of Bangong Lake-Dingqing limited Ocean and the further gathering of neighboring blocks later form it.There is a north-north-east negative anomaly belt of aerial magnetism in the middle-east part of the basin, which could be displayed by the aerial magnetism of commutative field, upwardly continuation, LVT in earthquakes, the experimentation of granite liquation (demagnetization) , the distribution of Neozoic era volcanic rock, earthquake, hot spring and ground feature. The anomaly shows the blocking in east-west direction, and it is also associated with intense activity of deep heat interaction and the development of the crust-mantle mixed layer in the North Qiangtang.We generally consider that the heat power in the deep of the basin is active, and the magmation is frequent, and that the type of the thermal structure is various.The analysis of the thermal structure is mainly focused on several different representative examples. (1) The first analysis is thermal structure of the collapse type in Quemocuo. There each group in Jurassic system is well developed, and there are two settlement-conglomeration centers of the period of Quemocuo and Xueshan. In prophase there existed thermal and magma activity, and before the更多还原