Lithostratigraphy, Structure, Geological History, Economic Geology and Paleontology of Mari Bugti Hills and Surrounding Areas of Balochistan, South Punjab and North Sindh (Pakistan)

Mari Bugti hills and surroundings belong to Sulaiman basin (fragment of Gondwana) lies under the territory of Balochistan, South Punjab and North Sindh (Pakistan) but luckily have diverse marine and terrestrial sediments varying in age from Triassic to Recent, petroleum and a large number of mineral resources especially huge gypsum and cement resources, numerous suitable anticlinal structures and world-famous paleontology. The large-sized poripuchian titanosaurs, theropods, mesoeucrocodiles, pterosaur, bird and snake were reported from the latest Cretaceous Vitakri Formation, and largest terrestrial mammals and eucrocodiles were reported from the Oligocene Chitarwata Formation and other mammals were also reported from Late Paleogene and Neogene terrestrial deposits. Previously part of this area was not mapped due to remoteness and security problems but recently the mapping of these areas was started. Further, the structural and geological maps of previously omitted parts are added here. After performing the multidisciplinary field investigations by senior author, the corresponding results were obtained. The main objective of this work is to focus on the lithostratigraphic deposits, structure, geological history, economic geology and paleontology of the Mari Bugti Hills and surrounding areas.

On the Origin of One Basin-Multiple Mountain Couplings in the Mesozoic-Cenozoic Basin-Range Area in Eastern North China

The basin-range coupling relation is a leading subject of the modern geology. In geometry, relations of this type include couplings between stretched orogenic belt and down-faulted basin, compressional orogenic belt and foreland basin, strike-slip orogenic belt and strike-slip basin and so on. Fault chains are the key for these couplings and there are typical examples for all these cases. The North China down-faulted basin is coupled west with the Taihang uplift, east with the Jiao-Liao Mountains, north with the Yanshan orogenic belt and south with the Dabie orogenic belt, that is to say, the central down-faulted basin and the surrounding orogenic belts bear a coupling relation within a uniform dynamistic system. Study shows that the central down-faulted basin and the North China mantle sub-plume structure have a close relation during their formation. Owing to intensive mantle sub-plume uplifting, the bottom of the lithosphere suffered from resistance, which caused the lithosphere of the eastern North China to be heated, thinned and fault-depressed. Meanwhile, mantle rocks that were detached outwards in the shape of mushroom was dissected by surrounding ductile shearing zones, which lead to decompression and unloading to generate hypomagmas, and a series of mantle-branch structures were formed around the down-faulted basin. There is an obvious comparability among these mantle branch structures (orogenic belts), and they have basin-range coupling relations with the central down-faulted basins.

THE ALTUN—NORTH QAIDAM ECLOGITE BELT IN WESTERN CHINA—ANOTHER HP-UHP METAMORPHIC BELT TRUNCATED BY LARGE SCALE STRIKE-SLIP FAULT IN CHINA

The Altun and North Qaidam Mountains at the northern margin of Qinghai\|Tibet plateau are separated by the Altyn Tagh sinistral strike\|slip fault, which is one of the largest strike\|slip fault systems in the world and was considered as the key element in the escape tectonics model for Euraisa\|India continent\|continent collision.Recently,the eclogites within quratzifeldspathic gneisses or pelitic gneisses characterized by amphibolite\|facies paragenesis were discovered in the Altun and the North Qaidam Mountains(Fig.1). They occur as lens or boundins within the Altun Group and Dakendaban Group respectively which previously were considered as metamorphic basement of Tarim block and Qaidam block. Our studies indicate that the eclogites outcrop in both the Altun and North Qaidam Mountains show similar occurrences, associated country rocks, rock and mineral assemblages, p\|T\% estimates, geochemistryand protolith feature and ages of peak metamorphism (see table) . The garnet\|omphacite\|phengite geothermobarometer gave equilibrium condition of \%p\%=2 8～3 0GPa and t =820～850℃ for the Altun eclogite and p =2 8GPa and \%t\%=730℃ for North Qaidam eclogite respectively(Fig..2). These p\|T conditions are in the coesite stability field. Moreover, Po lycrystalline quartz pseudomorphs after coesite have been identified in the Dulan area, North Qaidam Mountains (Song et al, in review). Therefore, these features suggest that both eclogites of Altun and North Qaidam Mountains probably are a same HP\|UHP metamorphic belt formed from the same of Early Paleozoic age deep subduction and collision, and subsequently displaced by the Altyn Tagh fault.The case is similar to the Dabie\|Sulu HP\|UHP metamorphic zone which was truncated by the Tanlu sinistral strike\|slip fault and splitted it into two distincts, the Dabie region and Sulu region. These correlations support an about 350～400km displacement of the Altyn Tagh sinistral strike\|slip fault (Fig.1).

ANISOTROPIC FEATURE OF QIANGTANG MASSIF TEXTURE

Qiangtang Massif is located in the hinterland of Qinghai—Tibet plateau, which belong to the mid\|east section of Tethys Tectonic Domain.1 Features of the whole texture and structure of Qiangtang massif By synthetic analysis of gravity,magnetic field,MT,seismic surveying,etc. Geophysical data, the massif, lied in the tectonic setting and geodynamic setting mingled by the south,north tectonic belts, have the features of massif,basin and tectonic belt three forming an organic whole,multi\|degree coupling in plane and section with division of region in south\|north trend,division of block\|fault in east\|west trend,division of sphere\|layer in vertical direction. (1) Belting in south\|north trend: Qiangtang massif could be divided into four units from north to south, that is north edge doming zone, west part doming area,Qiangtang Basin and south edge doming zone. Qiangtang Basin also can be divided into four tectonic units—north Qiangtang down\|warping region, middle downing zone, south Qiangtang down\|warping and east part slope region. The near east\|west trend tectonic zones are well developed. There is aero\|magnetic anomaly distributed in belting with east\|west trend but also concentrated in section. Gravity anomaly is high in the south\|west part and low in the northeast part. Inter\|crust low resistance layer alternately distributed with high and low belting of sou th\|north trend in plane.

Quaternary Geology and Faulting in the Damxung-Yangbajain Basin

The detailed geological mapping, conducted in the Damxung-Yangbajain basin, shows that there are many types of deposits formed since the Pliocene. The oldest sediments are formed during the Pliocene. The most prominent sediments are three sets of moraines and fluvioglacial deposits. The ESR, U-series and OSL dates indicate they are formed about 700-500 ka B.P., 250-125 ka B.P. and 75-12 ka B.P. respectively and indicate that there are three glacial periods since the mid-Pleistocene in the Nyainqentanglha Range. Along the southeast side of the Nyainqentanglha Range, the main southeast dipping fault zone which bounds the Damxung-Yangbajain Graben on its western edge was mapped. The fault zone consists of three secondary fault zones and their initiation ages that the fault zones became active gradually decrease southeastward. Prominent faulting occurred in about 700-500 ka B.P., 350-220 ka B.P., -140 ka B.P. and 70-50 ka B.P. since the mid-Pleistocene. The height of fault scarps which offset the sediments formed since the mid-Pleistocene suggest that the vertical slip rates change between 0.4 -2 mm/a and the cumulative average vertical movement at rates of 1.1±0.3 mm/a during the Quaternary period and the Holocene vertical throw rate is 1.4±0.6 mm/a along the fault zones on the western side of the Damxung-Yangbajain Graben.

3D Velocity Structure and Its Tectonic Implications in the East China Sea and Yellow Sea

3D structure of the crust and upper mantle in the studied area has been analyzed from surface wave tomography. The velocity distribution in the uppermost crust is symmetrical on two sides of the central line of the sea, and coincides with the structure of crystalline basement. The essential difference in tectonics between the East China Sea and the Yellow Sea mainly lies in that the velocity structures of their lower crust and upper mantle are identical to those of South China and North China respectively. In the upper mantle there exists a high-velocity zone with a nearly EW strike from the Hangzhou Bay, China, to the Tokara Channel, Japan, along about the latitude of 30°N. It is found that between the East China Sea and the Yellow Sea there are systematical differences in geomorphology, geology, seismicity, heat flow, quality factor and gravity and aeromagnetic anomalies, which is related to both left-lateral shear dislocation and right-lateral tear of the Benioff zone from the Hangzhou Bay to the Tokara Channel.It is inferred that the East China Sea was formed by Cenozoic back-arc extension. The boundary between the North China and South China crustal blocks stretches along the southern piedmont of Mts. Daba-Dabie-Hangzhou Bay-Tokara Channel, and the subduction zone at the Okinawa trench is the eastern boundary of the South China crustal block. The movements of the Pacific plate, Indian plate and upper mantle rather than the Philippine plate subduction have played a dominant role for the modern tectonic movements in East Asia.

北山区域额济纳旗大红山一带构造与成矿关系

北山地区位于甘肃省西北,西起新疆尾亚,东至内蒙古黑河绿园,南达甘肃瓜州,北抵中蒙边界,处于天山—阴山纬向构造带西段,东西长550 km,南北宽270 km,面积近15万平方千米。该地区构造复杂,区域构造主要由褶皱、断裂和变形构造等组成,自早古生代以来本区经历了拉张—俯冲—汇聚—碰撞—造山等长期而复杂的构造演化过程。

Apatite Fission Track Constraints on the Pattern of Faulting in the North Qilian Mountain

The Qilian （祁连） Mountain is an active orogenic belt located at the northeastern margin of the Tibetan Plateau. During the process of continuous convergence between Indian and Eurasian plates, the Qilian Mountain grow correspondingly by means of reaction of old faults and generation of new ones. Here we present apatite fission-track data along a river profile crossing three minor fault （the Minle （民乐）-Damaying （大马营） fault, the Huangcheng （皇城）-Taerzhuang （塔尔庄） fault and the Kangningqiao （唐宁桥） fault） which compose the North Qilian fault （NQF） to test the timing and pat- terns of the fault activities. Apatite fission-track （AFT） results indicate that these minor faults expe- rienced two active phases in the Cretaceous and the Oligocene-Miocene. Further research indicate that the initiation timing of faulting became younger northward in both active periods and the later phase probably more active than the former phase. These tectonic activities might be highly related to the docking of the Lhasa Block to the south in the Cretaceous and uplift and expansion of the Tibetan Pla- teau in the Cenozoic.

哀牢山—红河断裂带中南段新生代构造活动的年代学证据

运用同位素年代学研究哀牢山—红河断裂带的构造演化历史已获得众多成果,但尚未有从低温—中温—高温系统的角度构建热演化史过程的研究,断裂带左旋走滑的启动时间仍存在争议。总结了哀牢山—红河断裂带中南段的年龄数据,通过分析认为相同同位素体系厘定的年龄值从南东端到北西端变新,差异性减小;将研究区分为北、中、南3段,使用低温、中温、高温年龄构建时间-温度(T-t)变化曲线,热演化史表明断裂带经历了2期冷却历史,冷却速率和隆升剥蚀速率的时空变化记录了伸展应力自南向北依次传播、转换拉张强度在传递过程中逐渐减弱、断裂活动性明显减弱的过程;将断裂带构造活动划分为快速左旋走滑阶段(35~20 Ma)、左旋走滑逐渐减弱阶段(20~6 Ma)及右旋走滑阶段(6 Ma至今)。断裂构造活动反映了印度—欧亚板块碰撞过程中,青藏高原东南缘的应力持续调节过程。

广东普宁锡岭岗锡多金属矿地质特征及找矿方向

锡岭岗锡多金属矿锡矿体位于晚侏罗世黑云母二长花岗岩与下侏罗统上龙水组接触带,云英岩化、褐铁矿化强。矿床成因类型为热液裂隙充填矿床、工业类型为云英岩型矿床,岩体内外接触带、南北向次级断裂、云英岩化、硅化、化探元素组合异常和前人遗留老硐、旧坑等为重要的找矿方向。

石泉井水位异常与九寨沟7.0级地震关联性探讨

选取2014—2020年共计7年的石泉流体井水位整点值数据,结合小波分析方法及区域构造分析,研究石泉井水位长期异常变化的可能原因。结果表明,石泉水位异常活跃主要发生在2017年8月8日九寨沟地震之后,利用小波分析提取高频异常信息效果较好,九寨沟7.0级地震后的区域断裂活动加强或九寨沟地震造成的断裂周边含水层渗透性发生变化可能为导致石泉井水位长期异常的直接原因,未来月河断裂石泉段附近断层活动性值得进一步关注。

山西大同盆地恒山北缘断裂全新世古地震活动

野外调查表明 ,恒山北缘断裂断错了恒山北侧的洪积扇和恒山冲沟沟口的Ⅰ级阶地。地层测年资料表明 ,恒山北缘洪积扇中部、后缘以及恒山冲沟沟口Ⅰ级阶地的表层由距今约 5 2 0 0～ 6 80 0a的地层组成。位于恒山山前开挖的何庄及牛槽峪探槽揭示恒山北缘断裂在全新世早期以来曾发生过 3次古地震事件。这 3次古地震事件分别发生在 2 2 6 0± 190aBP～ 4 370±15 0aBP、接近 5 6 2 8± 15 0aBP和 80 83± 2 5 0aBP～ 84 30± 72 0aBP。 3次古地震事件的间隔为 2 313a及2 6 2 8a ,平均 2 4 71a。古地震事件的同震垂直位移为 1 0～ 3 0m。由于该断裂最新活动的离逝时间已超过全新世时期的古地震间隔 ,今后该断裂具备发生强震的可能 ,需加强观测。

玉溪—临沧剖面宽角地震探测——红河断裂带及滇南地壳结构研究

云南位于南北地震带南段,地震活动具有频度高、强度大的特点,中小地震几乎遍及云南南部,是中国大陆内部地震活动最强的地区之一.滇南地区跨越多个重要的地质构造单元和多条地震带,其中红河断裂带是跨越该地区的一条大型的走滑断裂带,作为印支地块和华南地块两大地块的分界断裂,对人们认识板块相互运动及其深部动力学背景具有重要意义.中国地震局于2010年启动了"中国地震科学台阵探测——南北地震带南段"项目,在云南省中西部跨越红河断裂带布设一条近东西向的深地震宽角反射/折射探测剖面,本文利用该东西向深地震宽角反射/折射剖面来研究红河断裂带及滇南地区详细的地壳结构及其孕震背景.研究结果表明:沿测线地壳结构呈西薄东厚的特征,以红河断裂带为界,断裂带以西地壳较薄,约34km,以东地壳加厚至44km左右;红河断裂带两侧速度结构具有明显的差异,断裂带西侧速度较低,东侧速度明显偏高.由震相特征及获取的地壳结构可以看出,红河断裂带两侧由浅至深速度结构的异常特征说明该古缝合带两侧块体地壳结构岩性的巨大差异性.

北天山西段库松木楔克山山前断层新活动特征初探

库松木楔克山山前断层是位于北天山西段再生造山带北缘一条重要的边界断层，是本次新发现和确定的一条活动断层。断层分为东、中、西三段：东段主要由4条断层斜列组合而成，单条断层长度为9～13km，在晚更新世～全新世仍在强烈活动，晚更新世以来的垂直错动量为3～4m，垂直活动速率为0．23～0．33mm／a，全新世以来的垂直错动量为0．5～0．8m；中段断层活动错断了中更新世至全新世地貌，形成多级断层陡坎和长约8～10km的地震形变带，晚更新世以来垂直活动速率为0．5mm／a；西段自晚更新以来无活动显示。

礼县—罗家堡断裂晚第四纪活动特征:兼论1654年礼县8级地震孕震机制

1654年7月21日甘肃省礼县8级地震发生在南北地震带的中北段,该地区的构造变形和构造活动与青藏高原向北东方向的扩展密切相关,复杂的构造几何特征主要受控于东昆仑断裂、西秦岭北缘断裂和一系列北东向断裂.礼县—罗家堡断裂为一条北东东向的左旋走滑活动断裂,错断了含有仰韶文化红色陶瓷片的一级阶地堆积物,阶地面上断层陡坎高约1.5m.沿断裂带发现冲沟的左旋位错量为3～10m,晚更新世黄土中残留的断层陡坎高4.5～8m.其中两条冲沟中发现裂点,高3.5～3.9m,距断层陡坎的距离为16m.礼县—盐关—罗家堡—天水镇一带发育大量的滑坡,长轴走向与礼县—罗家堡断裂一致,滑坡体后缘、侧壁陡峭,出露晚第四纪黄土,鲜有植被覆盖.礼县—罗家堡断裂为1654年8级地震的发震断裂.综合分析认为,受青藏高原向北东方向的扩展,被西秦岭北缘断裂、礼县—罗家堡断裂和岷县—宕昌断裂围限的礼县次级地块向南东滑动可能导致了1654年礼县8级地震的发生.断裂北、南两侧地壳电性结构的差异为强震的孕育提供了深部构造条件.

东海西湖凹陷断裂系统几何学特征及其成因机制

断裂系统几何学特征研究表明,西湖凹陷断裂样式具有显著的"东西分带、南北分块"特征。西部斜坡带北部和南部为断阶式构造样式,中部的平湖斜坡带主要为单断式;中央-洼陷反转构造带自北向南构造样式呈规律性变化,反映出断裂反转强度自北向南减弱的趋势;东缘陡坡断隆带北部以西倾的同向断阶式为主,南部以东倾的反向断阶为主,中部黄岩边缘断裂带呈过渡特征。各主要构造带南北构造样式的转换部位也具有特殊的构造现象,凹陷中南部主要表现为晚期近E—W向断裂的集中发育,两侧NE、NNE向断层多尖灭或横向错移,中北部主要表现为断裂走向的变化。构造带南北构造样式的转换部多位于区域NW、NWW向基底断裂的延伸线上,这类NW、NWW向基底断裂多具有走向平移特征,据此,笔者认为这种构造特征的南北差异可能与早期NW、NWW向基底调节断裂的限制或再活动有关,在此基础上提出了西湖凹陷断裂样式南北差异的成因演化模式。

南黄海盆地北部坳陷海底油气渗漏的声学探测

为查明南黄海盆地北部坳陷调查区内与海底油气渗漏有关的海底浅表层声学特征,分析天然气渗漏与构造的关系,为下一步地球化学取样站位的选择和油气勘探提供参考,采用全覆盖侧扫声纳和高分辨率地震方法首次对调查区的海底油气渗漏现象进行了调查。在镶嵌处理后的侧扫声纳图像上,呈条带状散布的强反射斑块为麻坑和海底圆丘地貌。在地震剖面上可见由于气体聚集产生的振幅增强、柱状扰动、气窗及空白反射等特征。分析结果表明,广泛发育的接近或直达海底的断层为油气渗漏提供了通道和气源,海底浅表层气体的聚集和渗漏是深部地层中孔隙流体向上运移的结果,且调查区海底目前仍处于微渗漏阶段。

华山新生代隆升—剥蚀历史的裂变径迹热年代学分析

综合分析前人的热年代学数据发现华山地区自晚白垩世以来至少经历了三次快速隆升阶段,在120～57Ma间华山经历了缓慢隆升过程,约57Ma以来华山开始相对渭河地堑的快速隆升。其中,57～42Ma间、32～22Ma间和约8Ma以来均为相对快速隆升阶段,视隆升速度约为0.18～0.23mm/a;而42～32Ma间和22～8Ma间则为相对缓慢隆升过程,视隆升速度约为0.01mm/a。约57Ma以来华山的隆升-剥蚀量约为8.5km,平均隆升速度约为0.15mm/a;约32Ma以来的总隆升幅度约为4.5～5.1km,平均视隆升速度约为0.14～0.16mm/a。晚中生代以来华山的隆升过程实际上反映的是东秦岭的隆升过程,与区域地貌结构和周缘断陷盆地的演化过程有密切的成因联系,它表明东秦岭地区的三级等高峰顶面是120～57Ma、42～32Ma和22～8Ma间山脉缓慢隆升-剥蚀的结果,同时反映57～55Ma是渭河盆地开始快速裂陷和秦岭北麓正断层开始强烈活动的时间。

关于岷江断裂若干问题的讨论

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