帕米尔东北缘新生代隆升活动:来自奥依塔格剖面砾石统计的证据

砾岩相通常作为构造事件的标志,对探讨造山带隆升过程有着重要的意义.选取位于帕米尔构造带东北缘的奥依塔格剖面开展砾石统计分析.新生代不同时期砾石的统计结果显示,奥依塔格剖面砾石成分主要为火成岩和变质岩,这与帕米尔造山带岩性相符.其中,花岗岩砾石作为特征组分首次出现在上新统阿图什组底部.砾石主要为巨砾,且以长短轴比值为1~2的近圆状为主;砾石的磨圆度中等,绝大部分为次磨圆-次棱角状;分选中等-差.结合砾石所处地层的沉积环境和热年代学记录,认为帕米尔东北缘新生代可能存在3期构造隆升事件,包括渐新-中新世克孜洛依组沉积早期、中新世中期(安居安组中-上段和帕卡布拉克组下段沉积时期)和上新世以来(阿图什组下段沉积以来).      

新疆南天山阿沙哇义金矿床的成因与找矿启示:来自流体和硫化物成分的限定

阿沙哇义金矿位于中国新疆南天山造山带,属于著名的中亚南天山锑-汞-金成矿带的东延部分。该矿床严格受断裂所控制,以浸染状黄铁矿化、毒砂化为特征。矿化可分为三个阶段:早期无矿或贫矿石英阶段,中期石英多金属硫化物阶段,晚期石英-碳酸盐阶段。其中,中期是主要成矿阶段。成矿流体气相成分以H_2O为主,摩尔含量为75%～93%,其次为CO_2,摩尔含量为6%～25%,其余为CH_4、C_2H_6、H_2S、N_2和Ar;液相成分阳离子以Na~+为主,含少量K~+、Ca~(2+)离子,阴离子以Cl~-为主,SO~(2-)次之;矿石的Au含量与其流体的CO_2含量呈反相关,与K~+含量呈正相关。硫化物成分分析结果表明:(1)围岩地层和矿石中的黄铁矿和毒砂是重要的载金矿物,黄铁矿Au含量为0～0. 09%,平均值0. 03%;毒砂Au含量为0～0. 28%,平均值0. 07%;(2)黄铁矿和毒砂Au含量与其自形程度没有明显的相关性;(3)环带状黄铁矿较均质结构黄铁矿具有更高的Au含量;(4)岩体中的黄铁矿几乎不含Au。在成矿构造环境、成矿流体特征及演化、金矿富集机制、成矿温压条件等方面,该矿床与世界上大多数造山型金矿显示出一致性,成矿类型应属于剥蚀程度较浅的造山型金矿。断层阀作用控制的断层愈合-破裂导致的流体不混溶作用是本区金富集、沉淀的最重要机制,但流体混合机制对金的富集沉淀也发挥了作用。黄铁矿、毒砂发育及较多的含炭物质三者共存是本区寻找富矿的关键标志。     

兴蒙造山带构造演化的新模式:来自内蒙古中部四期不同类型变质作用的证据

有关中亚造山带东段即兴蒙造山带早古生代以来的构造演化一直倍受关注,其中争议最大的问题是古亚洲洋最终闭合的时间究竟是在泥盆纪还是早中生代?晚古生代的大地构造背景究竟是持续的大洋俯冲还是经历了造山后的伸展裂解过程?以往对内蒙中部地区的研究多数局限于区域内广泛分布的蛇绿岩和各类型岩浆岩的年代学和地球化学,但是通过地球化学的方法来确定一个地区的构造环境往往具有多解性。为建立研究区的构造框架并查明兴蒙造山带构造演化过程,本文详细总结了内蒙古中部地区变质作用的最新研究进展,对兴蒙造山带的演化提出了新的认识。确定了该区域在古生代以来的变质作用可分为四期:第一期为志留纪的高压低温型(430～410Ma),以南、北带的温都尔庙群蛇绿混杂带为代表,发育典型的低温高压型蓝片岩相岩石,记录了洋壳的双向俯冲过程;第二期为早-中泥盆世的中压型(～400Ma),以宝音图群为代表,发育典型的巴罗型变质带,经历以升温升压为特征的前进变质、峰期变质、峰后近等温降压以及随后降温降压的顺时针型P-T演化,指示与地壳加厚有关的碰撞造山过程;第三期为石炭纪的低压高温型(345～309Ma),以锡林郭勒杂岩低压变质岩为代表,发育广泛的混合岩化和基性岩脉的侵入,经历早期升温伴随微弱减压,直至温度峰期后近等压冷却的顺时针P-T演化,指示造山后的陆内伸展过程;第四期为早三叠世(～240Ma)的中-低压低温型,以早三叠世区域低级变质岩系为代表,经历中-低压相系的顺时针P-T演化,指示与有限海盆闭合有关的陆内造山过程。结合已有的研究,内蒙古中部地区晚古生代的火山岩和侵入岩更可能形成于伸展的构造环境,超基性岩和沉积岩系的时空配置与典型大洋的蛇绿混杂岩明显不同,更可能形成于有限海盆的环境。因此,从四期变质作用来看,兴蒙造山带的构造演化可能更符合复合造山的模式:(1)早古生代古亚洲洋发育沟弧盆体系(500～410Ma);(2)早-中泥盆世古亚洲洋闭合引发陆陆碰撞造山(～400Ma);(3)石炭-二叠纪陆内伸展并形成有限海盆(350～250Ma)和(4)早-中三叠世有限海盆被动闭合引起板内造山(～240Ma)。     

龙门山中北段印支晚期构造活动:来自构造解析及碎屑锆石年代学的证据

晚三叠世是四川盆地演化过程中的重要阶段,该时期盆地西部经历了从被动大陆边缘向前陆盆地的演变.为进一步厘定龙门山中北段印支晚期构造的具体活动时间及活动强度,本研究选择龙门山前中北段某地震剖面进行构造几何分析,结果显示龙门山前中北段大规模的逆冲推覆很可能在须家河组四段沉积初期就已经出现,其恢复的推覆位移量至少达到11 km...     

秦岭——大别造山带与江南造山带的差异隆升过程:来自江汉盆地中新生代沉积记录的证据

江汉叠合盆地地处扬子地区中部,夹持于秦岭——大别造山带与江南造山带中段之间,是中生代中期以来在扬子浅海台地基础上发育起来的典型海陆交互相-陆相叠合盆地,其中充填了厚逾10000m的中三叠世-新近纪陆源碎屑岩系。据印支期以来的造山活动历程与成盆演化特点,将盆山耦合过程划分为造山前期、主造山期、造山后期与非造山期4个阶段,将盆地充填层序划分为陆架边缘、前陆、断陷和坳陷4个(盆地世代)超层序。依据盆内沉积物碎屑组份分析,发现中三叠世江南造山带进入强造山活动期,白垩纪末进入造山带坍塌后的活动平静期;秦岭——大别造山带的主造山活动阶段为晚三叠-早侏罗世,古近纪末处于非造山活动相对平静阶段。盆区整体呈现东部造山活动早,山带隆升早,持续时间长,剥露地层较快较早进入变质岩层段;西部造山活动时间晚,隆升时间相对较晚,剥露地层在早侏罗世初期才依次切入变质岩层段;盆地南、北缘山带总体呈现多幕式差异隆升过程。     

西南天山新生代造山岩浆作用响应——以皮羌盆地新生代火山岩为例

新疆西南天山皮羌盆地是一个新生代火山构造盆地。盆地内出露4个古火山颈和大量岩墙,部分岩墙与火山颈相连。运用岩相学、岩石地球化学测试分析法研究皮羌盆地内火山岩,研究表明,火山岩具原生岩浆性质,及碱玄岩、碧玄岩和玄武岩岩石组合特征。火山岩产于板内造山带环境,为幔源部分熔融产物,无明显结晶分异。结合托云盆地新生代火山岩岩石地球化学探讨西南天山岩浆触发机制,认为岩石圈局部拆沉作用是触发本区岩浆活动主要机制。     

Late Cenozoic Tectonics Along the Northwestern Margin of the Tarim Basin: Interactions Between the Tarim Basin and the Southern Tian Shan, West China

LATE CENOZOIC TECTONICS ALONG THE NORTHWESTERN MARGIN OF THE TARIM BASIN: INTERACTIONS BETWEEN THE TARIM BASIN AND THE SOUTHERN TIAN SHAN, WEST CHINAgrants 4 98340 50and 4 9732 0 90fromtheNSFofChina;;andproject96 913 0 7 0 1fromtheMinistryofSci enceandTechnology ,China…     

Paleoseismological Study of the Late Quaternary Slip-rate along the South Barkol Basin Fault and Its Tectonic Implications, Eastern Tian Shan, Xinjiang

The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault(SBF) in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Quaternary activity, paleoseismology, and deformation characteristics of the fault provide important clues for understanding the tectonic process of the eastern Tian Shan orogen and implementing seismic mitigation. Through interpretation of high-resolution satellite images, unmanned aerial vehicle measurements, and detailed geological and geomorphic investigations, we suggest that the fault exhibits clear left-lateral slip along its western segment. Paleoseismic trenches dug near Xiongkuer reveal evidence of six large paleoearthquakes. The four latest paleoearthquakes were dated: the oldest event occurred at 4663 BC–3839 BC. Data on the horizontal offsets along the probable 1842 Barkol earthquake coseismic rupture suggest clear multiple relationships between cumulative offsets and possible ~4 m of coseismic left-lateral slip per event. From the cumulative offsets and 14 C sample ages, we suggest an average Holocene left-lateral slip rate of 2.4–2.8 mm/a on the SBF, accounting for ~80% of lateral deformation within the entire eastern Tian Shan fault system. This result is comparable with the shortening rate of 2–4 mm/a in the whole eastern Tian Shan, indicating an equal role of strike-slip tectonics and compressional tectonics in this orogen, and that the SBF may accommodate substantial lateral tectonic deformation.     

Multistage Enrichment of the Sawafuqi Uranium Deposit: New Insights into Sandstone-hosted Uranium Deposits in the Intramontane Basins of Tian Shan, China

Meso-Cenozoic intracontinental orogenic processes in the Tian Shan orogenic belt have significant effect on the sandstone-hosted uranium deposits in the intramontane basins and those adjacent to the orogen. The Sawafuqi uranium deposit, which is located in the South Tian Shan orogenic belt, is investigated to reveal the relationships between uranium mineralization and orogenies. Recent exploration results show that the Sawafuqi uranium deposit has tabular, stratiform, quasi-stratiform, and lens-like orebodies and various geological characteristics different from typical interlayer oxidation zone sandstone-hosted uranium deposits. Systematic studies of ore samples from the Sawafuqi uranium deposit using a variety of techniques, including thin section observation, α-track radiograph, electron microprobe and scanning electron microscope, suggest that uranium mineralization is closely related to pyrite and organic matter. Mineralization-related alterations in the host rocks are mainly silicification and argillation including kaolinite, illite(and illite-smectite mixed layer) and chlorite. Tree stages of mineralization were identified in the Sawafuqi uranium deposit:(i) uranium-bearing detritus and synsedimentary initial pre-enrichment;(ii) interlayer oxidization zone uranium mineralization; and(iii) vein-type uranium mineralization. The synsedimentary uranium pre-enrichment represents an early uranium enrichment in the Sawafuqi uranium deposit, and interlayer oxidation zone uranium mineralization formed the main orebodies, which are superimposed by the vein-type uranium mineralization. Combining the results of this study with previous studies on the Meso-Cenozoic orogenies of South Tian Shan, it is proposed that the synsedimentary uranium pre-enrichment of the Sawafuqi uranium deposit was caused by Triassic Tian Shan uplift, and the interlayer oxidation zone uranium mineralization occurred during the Eocence-Oligocene period, when tectonism was relatively quiet, whereas the vein-type uranium mineralization took place in relation to the strong orogeny of South Tian Shan since Miocene.     

龙门山晚新生代地表剥蚀量的定量估算

龙门山是青藏高原周边山脉中地形梯度变化最大的山脉.利用数字高程模型(digital elevation models, DEM),采用三维残余面法恢复龙门山晚新生代古残余面DEM,并与现代地形面做差值运算,得到研究区域的剥蚀量地形,进而定量估算青衣江、岷江、沱江和涪江主要水系流域晚新生代的地表剥蚀量.结果表明:龙门山晚新生代地表剥蚀总量为80 500~92 800 km3;岷江流域对龙门山地区剥蚀量贡献率约33.9%~37.1%,其次为涪江(33.6%~38.4%)、青衣江(24.1%~31.9%),沱江流域贡献率为0.4%~0.6%;类似2008年“5·12”汶川地震的次生灾害引发的地表快速剥蚀,是青藏高原东缘龙门山造山带晚新生代地表剥蚀的主要原因.      

西南天山前陆盆地侏罗纪-白垩纪盆山格局——来自碎屑锆石年代学的证据

目前对天山地区,特别是天山南缘中生代盆山格局认识尚存分歧。本文着眼于侏罗纪-白垩纪这一盆山演化关键阶段,利用碎屑锆石LA-ICP-MS U-Pb定年法对西南天山前陆盆地康苏剖面中侏罗统杨叶组、下白垩统克孜勒苏群沉积开展物源分析。发现中侏罗统杨叶组碎屑锆石U-Pb年龄分布于369~2687 Ma间,基本分布在369~404 Ma(约占4%)、418~501 Ma(约占19%)和544~2687 Ma(约占77%)3个范围;下白垩统克孜勒苏群碎屑锆石U-Pb年龄分布于243~2820 Ma间,集中于253~414 Ma(约占35%)、423~489 Ma(约占27%)和668~2820 Ma(约占37%)3个范围。中侏罗统碎屑锆石年龄分布范围广,各年龄组分均较突显,反映中侏罗世西南天山前缘流域体系宽广,天山内各主要源区均得到沟通,物源范围广阔。下白垩统克孜勒苏群锆石年龄分布明显集中,反映早白垩世西南天山前缘源区范围有所缩小。西南天山前缘与库车前陆盆地的物源构成在中侏罗世存在一定差异,而在早白垩世呈现相似特征。包括西南天山前陆盆地在内的天山南缘或于早白垩世经历一期小规模构造反转,导致山-盆构造分异与抬升-剥蚀增强。     

Development of Tectonic Geomorphology Study Promoted by New Methods in China: A Viewpoint from Reviewing the Tian Shan Researches

Tectonic Geomorphology is an important branch of Geomorphology. Now the scope of tectonic geomorphology study has covered the interactions between tectonics, climate, surface processes and the influence on geomorphic evolution. The study of tectonic geomorphology in China started at the beginning of the 20th century, developed gradually in the 1950s, and entered a rapid development stage in the new century. Based on the long-term development, the study of tectonic geomorphology in China has formed a relatively complete theoretical and methodological system, and now presents a trend of the continuous intersection and integration with other adjacent disciplines. Now, several books on tectonic geomorphology have been published. The representative book abroad is Tectonic Geomorphology which was edited by Burbank D. W. and Anderson R. S., and was first published in 2001 and reprinted in 2012. In China, the first book on tectonic geomorphology is Active Tectonic Geomorphology which was edited by Yang Jingchun and Li Youli and was first published in 2011.In recent years, the tectonic geomorphology study has been absorbing and integrating the new ideas and new methods of other disciplines, significantly promoting the development of tectonic geomorphology. At the 2019 China Geographic Congress & the 110th anniversary of the establishment of the Chinese Geographical Society, the authors organized the session "Theory, Method and Application of Tectonic Geomorphology", aiming to present the recent progresses of tectonic geomorphology study in China. Later, invited by the editorial office, the authors organized the special column with the same name in the journal Advances in Earth Science. The contents of this column mainly dealt with the classical theoretical problems of geomorphology (the evolution and the controlling mechanism of river terrace, planation surface, and alluvial fan), new methods (such as K-feldspar thermoluminescence thermochronology, detrital zircon U-Pb chronology), and models and numerical simulation of tectonic geomorphology evolution. Because of the limited number of the articles, it was impossible for this column to comprehensively present the recent progresses in the study of tectonic geomorphology in China. Therefore, this paper first briefly reviewed the history of the development of tectonic geomorphology in China and the basic trend of tectonic geomorphology. The authors started the study of neotectonics and tectonic geomorphology in the Tian Shan range and its foreland basins about 15 years ago (exactly in 2002). The main aim of this paper was to explore the contributions of the interdisciplinary and new methods to the development of tectonic geomorphology study, by reviewing the main achievements in the tectonic geomorphology study conducted in the Tian Shan and its foreland basins during the past 20 years. These achievements include the history of uplift and exhumation during the Cenozoic times, the chronology and genesis of the late Cenozoic terrigenous sedimentary sequences in the foreland basins, the characteristics of the late Quaternary active tectonic deformation in the foreland and intermontane basins, the late Quaternary river geomorphology (geomorphic framework, chronology, and cause of formation), and erosion rates of the catchment basins. At the end of this paper, it was pointed out that, two aspects may need more attention in the future tectonic geomorphology study, i.e. the comparative study at different time scales and the better constraint of the formation age of river terrace.     

基于ASTER VNIR-SWIR多光谱遥感数据识别与提取干旱地区岩性信息——以西南天山柯坪隆起东部为例

ASTER多光谱遥感数据目前可以用于岩石矿物资源信息的识别和提取。本研究尝试利用ASTER可见光近红外(VNIR)和短波红外(SWIR)的多光谱遥感数据提取干旱地区的岩石与矿物信息。基于新疆天山西南缘柯坪隆起东部不同地层单元岩石的化学组成和矿物成份以及VNIR-SWIR谱域光谱吸收特征的分析,我们采用相关吸收波段深度(RBD)和波段比值(BR)方法对研究区的多光谱遥感数据进行图像处理,有效区分和识别了白云岩、石灰岩、砂岩以及阿克苏群的蓝片岩—绿片岩和砂质片岩。白云岩的CO_3~(2-)吸收谱带中心波长位于2.32μm,与灰岩的CO_3~(2-)吸收谱带中心波长位置2.35μm相比,具有向短波长方向移动的特点,据此可以利用RBD7、RBD8分别有效的识别白云岩和灰岩;长英质岩石显示Al-OH和Fe~(3+)VNIR-SWIR吸收特征,而基性-超基性岩石显示Fe~(2+)和Fe、Mg-OH特征,利用不同的铁价态和次要矿物可以区分它们:ASTER band2/band1代表了含Fe~(3+)矿物分布信息、ASTER band5/band4代表了含Fe~(2+)矿物分布信息、RBD6可以估计Al-OH矿物的丰度;砂质/泥质片岩含较多的多硅白云母、绿泥石、黑硬绿泥石以及风化后表面覆盖的其它粘土矿物,在2.21μm(band6)存在有特征的吸收谱带,并且在1.65μm(band 4)具有较高的反射率,而蓝片/绿片岩在2.21μm(band 6)反射率较高,不具有明显特征吸收谱带,同时其在1.65μm(band 4)反射率较低,因此蓝片/绿片岩ASTER band4/band6比值低。应用ASTER band4/band6波段比值可以有效的区分开砂质/泥质片岩与蓝片岩/绿片岩。     

西天山卡特巴阿苏金矿床成矿年代学及其地质意义-来自绢云母~(40)Ar-~(39)Ar同位素年龄证据

新疆卡特巴阿苏金矿床是近年来在西天山地区新发现的一个大型金矿床。该矿床大地构造位置处于塔里木板块和哈萨克斯坦-准噶尔板块结合部位的那拉提构造-岩浆岩带,其金矿体主要赋存于蚀变二长花岗岩内。为了确定金矿化的形成时代,对该矿床主成矿阶段与金矿化密切相关的蚀变绢云母开展了40Ar-39Ar同位素定年测试。绢云母40Ar-39Ar坪年龄为(268.56±1.8)Ma,正等时线年龄为(268.38±2.2)Ma,反等时线年龄为(268.52±2.2 Ma),三者在误差范围内一致,测试结果可信,可代表卡特巴阿苏金矿化的形成年龄,这也是首次对该矿床成矿年龄的精确限定。对比中亚造山带典型金矿床,卡特巴阿苏金矿床是西天山二叠纪后碰撞构造环境下岩浆流体活动的产物,矿床成因属与中温岩浆热液有关的构造蚀变岩型矿床。