The Koshrabad granite massif in Uzbekistan: petrogenesis, metallogeny, and geodynamic setting     

D.L. Konopelko  Yu S. Biske  K. Kullerud  R. Seltmann  F.K. Divaev 《Russian Geology and Geophysics》2011,52(12):1563-1573

The Koshrabad massif, referred to as the Hercynian postcollisional intrusions of the Tien Shan, is composed of two rock series: (1) mafic and quartz monzonites and (2) granites of the main phase. Porphyritic granitoids of the main phase contain ovoids of alkali feldspar, often rimmed with plagioclase. Mafic rocks developed locally in the massif core resulted from the injections of mafic magma into the still unconsolidated rocks of the main phase, which produced hybrid rocks and various dike series. All rocks of the massif are characterized by high f (Fe/(Fe + Mg)) values and contain fayalite, which points to the reducing conditions of their formation. Mafic rocks are the product of fractional crystallization of alkali-basaltic mantle melt, and granitoids of the main phase show signs of crustal-substance contamination. In high f values and HFSE contents the massif rocks are similar to A-type granites. Data on the geochemical evolution of the massif rocks confirm the genetic relationship of the massif gold deposits with magmatic processes and suggest the accumulation of gold in residual acid melts and the rapid formation of ore quartz veins in the same structures that controlled the intrusion of late dikes. The simultaneous intrusion of compositionally different postcollisional granitoids of the North Nuratau Ridge, including the Koshrabad granitoids, is due to the synchronous melting of different crustal protoliths in the zone of transcrustal shear, which was caused by the ascent of the hot asthenospheric matter in the dilatation setting. The resulting circulation of fluids led to the mobilization of ore elements from the crustal rocks and their accumulation in commercial concentrations.  相似文献   

Strong historical earthquakes in the northwestern Issyk Kul’ basin (northern Tien Shan)     

A.M. Korjenkov  S.V. Abdieva  A.B. Dzhumabaeva  A.B. Fortuna  E. Mamyrov  E.A. Morozova  L.A. Orlova  P.S. Vakhrameeva 《Russian Geology and Geophysics》2011,52(9):1007-1015

The northern Tien Shan is the northern front of the Himalayan mountain belt, which resulted from the collision between the Indian and Eurasian Plates. This region encompasses the most active seismic zones of the orogen, which generated the strongest (M > 8) earthquakes. Since there are scarcely any written accounts, the only way to trace back strong earthquakes is the paleoseismologic method. Since 1984 we have been studying the northwestern Issyk Kul’ basin, where there are differently directed anticlines, which constitute the Kungei meganticline. Here, several active tectonic structures (faults, folds) are located, whose development was accompanied by strong earthquakes. Our field studies of 2008 in the Iiri-Taldybulak Valley, along the adyrs (foothills) of the Kungei-Ala-Too Range, revealed two unknown historical earthquakes. The first one, which occurred along the southern rupture in the late 7th century A.D., gave rise to a seismic scarp; the latter broke through the river floodplain and a tash-koro (ancient settlement). The second one, which occurred along the northern rupture in the late 9th century A.D., increased the height of the seismic scarp, existing on the Early Holocene and older terraces. Note that this region already records a strong seismic event around 500 A.D. Archeologic data have revealed one more strong earthquake, which took place in the 14th century A.D. Note that the above-mentioned strong seismic events are coeval with the decline of the nomadic cultures (Wusun, Turkic, Mogul) in the northern Tien Shan and Zhetysu (Semirech’e).  相似文献   

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     

高永伟 《地质与勘探》2015,51(5):805-815

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。  相似文献   

鄂尔多斯盆地子洲气田上古生界山西组、下石盒子组储集层特征对比研究   总被引：2，自引：0，他引：2       下载免费PDF全文

王若谷  李文厚  廖友运  冯永玖  郭艳琴  马瑶  许星 《地质科学》2015,50(1):249-261

鄂尔多斯盆地子洲气田山西组山2~3段和下石盒子组盒8段是该区天然气的主力储集层,但其产能却存在很大差异。应用薄片鉴定、扫描电镜、高压压汞、恒速压汞及岩心分析资料,分别对该地区上古生界山西组山2~3段和下石盒子组盒8段储集层进行了研究。子洲气田山2~3储层以石英砂岩为主,孔隙类型多样,粒间孔、溶孔、晶间孔发育,喉道类别以微—细喉为主,属相对低孔高渗型储层;盒8储层则以岩屑砂岩为主,孔隙类型主要为岩屑溶孔和晶间孔,喉道类别以细—微喉为主,属于相对低孔低渗型储层。山2~3段和盒8段储集层岩石类型、孔隙结构差别巨大,造成了其储集性能的差异性。不同的沉积环境和成岩作用是造成其差异性的主要原因。  相似文献   

The Major Two-stage Shortening Deformation of the Northern Tibet and Tian Shan Area Since the Latest Oligocene     

LU Haijian  LI Haibing  LIU Dongliang 《《地质学报》英文版》2015,89(5):1546-1560

It seems to be progressively recognized that the stress of the India-Asia convergent front can be transferred rapidly through the southern and central Tibetan lithosphere to the northern Tibet, hence leading to the crustal thickening deformation there during or immediately after the onset of the India-Asia collision(ca.55 Ma).This study focuses on the late Cenozoic deformation and tectonic uplift of the northern Tibet and Tian Shan area.Detailed compilations of a variety of proxy data from sediments and bedrocks suggest that the northern Tibet and Tian Shan area underwent one stage of approximately synchronous widespread contractile deformation since 25–20 Ma, which seemed to decrease at circa 18 Ma as revealed by low-temperature thermochronological data.The latest Oligocene-early Miocene was also significant basin-forming episodes when many intermontane subbasins began to receive syntectonic sedimentation in the northeastern Tibet.Subsequently, the other phase of compressional deformation began to encroach more widely into the northern Tibet and Tian Shan area in episodic steps or continuously from 16–12 Ma to present.  相似文献   

龙门山晚新生代地表剥蚀量的定量估算          下载免费PDF全文

王岩  刘少峰  付碧宏  邢树文 《地球科学》2015,40(6):953-964, 1060

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.   相似文献   

Physico-chemical characteristics and environmental significance of snow deposition on Haxilegen glacier No.51 in Tian Shan, China     

Zhiwen Dong  Zhongqin Li  Mingjun Zhang  Feiteng Wang  Lihua Wu 《山地科学学报》2011,8(3):484-494

Snow chemistry on the glaciers of alpine regions is a good indicator of atmospheric environmental change.We examine snow chemistry in three snowpits at different altitudes on the Haxilegen Glacier No.51,in the Kuitun River source,Tian Shan,China,during July-September 2004 to 2007.We use correlation analysis,factor analysis and sea-salt tracing methods to examine the characteristics and sources of major ions and mineral dust particles in the snow.Results show that mineral dust particles and major ions in the snow pits vary seasonally.During the Asian dust period in springtime,the concentration of mineral dust particles and major ions deposited in snow is high,while the concentration is relatively low during the non-dust period of summer and autumn.This may be caused by dust storm activity in central Asia.The order of major ionic concentrations in the snow packs was determined to be Ca2+ > SO42-> NH4+ > NO3-> Cl-> Na+ > Mg2+ > K+.Ca2+ was the dominant cation;SO42- was the dominant anion.We find,with the exception of NO3-,that the variabilities of ionic concentrations are highly correlated.Results show that the glacier region was significantly affected by dust activity and anthropogenic source.The major ions,especially Na+,originate from dust sources of central Asia and from the Ocean,transported by the westerly winds.  相似文献   

天山构造带及邻区地壳各向异性   总被引：2，自引：0，他引：2       下载免费PDF全文

鲍子文  高原 《地球物理学报》2017,60(4):1359-1375

天山构造带位于中国大陆西北部,是典型的岩石圈陆内缩短造山带.本文利用新疆区域数字地震台网2009年1月至2014年12月的近场小地震波形资料,采用剪切波分裂分析对天山构造带及邻区的地壳各向异性特征进行研究,获得了研究区域内39个台站的快剪切波偏振方向和慢剪切波时间延迟.剪切波分裂参数的空间特征显示,研究区上地壳各向异性具有分区性,各向异性特征与局部构造、地壳介质变形和应力分布有关.天山构造带的快剪切波偏振呈现出两个优势方向的特点,第一优势方向大致平行于台站附近断裂和天山构造带的走向,与断裂构造和应力的综合影响有关,另一个优势方向反映了主压应力的直接作用.北天山山前断裂带东段的断裂弯折部位和南天山局部地区的剪切波分裂参数与东、西两侧不同,与准噶尔盆地、塔里木盆地的南北向挤压作用密切相关.快剪切波偏振优势方向的剧烈变化揭示,在准噶尔盆地和塔里木盆地双向挤压隆起的过程中,天山构造带产生了强烈的局部不均匀变形.塔里木盆地西侧快剪切波偏振具有两个优势方向,一个为NNE方向,与帕米尔高原受到印度一欧亚板块碰撞产生的北向挤压作用有关,另一个为NW方向,指出了塔里木盆地区域主压应力方向.准噶尔盆地北部也存在NE和NW两个快波偏振优势方向,主要与断裂的影响有关.天山构造带区域内的慢剪切波时间延迟总体上低于塔里木盆地西侧和准噶尔盆地北部,同时慢剪切波时间延迟的结果也进一步证实了天山构造带的局部强烈变形.  相似文献   

青藏高原东北缘玛雅雪山晚第四纪冰川发育的气候和构造耦合   总被引：2，自引：1，他引：1  

刘蓓蓓  张威  崔之久  刘亮 《冰川冻土》2015,37(3):701-710

青藏高原东北缘的玛雅雪山(海拔4 447 m)保存着确切的第四纪冰川遗迹. 野外地貌调查与光释光测年方法相结合, 确认玛雅雪山晚第四纪主要经历3次冰川作用: 第Ⅰ组冰碛时代为新冰期; 第Ⅱ组冰碛物年龄为(23.2±1.0)ka, 其上覆泥石流年龄为(2.9±0.3)~(2.3±0.1)ka, 上层土壤年龄为(3.6±0.2)ka, 对应于深海氧同位素2阶段(MIS 2)的末次冰盛期(LGM); 第Ⅲ组冰碛年龄为(42.6±1.9)~(45.7±3.0) ka, 属于末次冰期中冰阶, 对应MIS 3中期. 采用最新综合因子法计算玛雅雪山现代冰川物质平衡线为海拔4 605 m. 依据冰川地貌形态, 计算末次冰期平衡线为海拔3 800 m. 通过庄浪河阶地的拔河高度及各级阶地的年代, 以河流的下切速率代表玛雅雪山的抬升速率, 计算得到末次冰期中期以来玛雅雪山抬升了50~60 m. 利用玛雅雪山周边的达里加山和太白山冰川漂砾的¹⁰Be 数据近似代表流域侵蚀速率, 推算出玛雅雪山剥蚀速率大约为29 mm·ka^-1, 推断MIS 3以来流域的剥蚀量为1~2 m. 综合末次冰期中期以来的构造抬升量和剥蚀量, 恢复末次冰期中期时的流域高度为海拔4 200 m, 平衡线高度为海拔3 750 m. 研究结果显示: 研究区在MIS 3时, 流域平均高度已经在平衡线之上, 在流域平均高度到主峰之间冰川开始积累, 发育冰川. 结合其他环境指标综合推断, 玛雅雪山晚第四纪冰川的发育是气候和构造耦合的产物.  相似文献   

京张地区区域地壳稳定性评价   总被引：3，自引：3，他引：0  

张树轩  杨为民  孟华君  张向营  李焕斌 《地质力学学报》2018,24(1):70-77

在野外调查和广泛收集资料的基础上,分析了控制和影响京张地区区域地壳稳定性的主要因素及内外动力地质的耦合作用。选取活动断裂、地震活动性和深部地球物理等因素,同时选取工程岩组、地形地貌与地表地质灾害等11个因素作为评价因子,并对评价因子进行了分类赋值。采用多因素加权叠加分析方法,建立了区域地壳稳定性评价模型,基于GIS平台对京张地区的区域地壳稳定性进行了定量化评价,将研究区划分为稳定区、次稳定区、次不稳定区和不稳定区4个等级。依据区域地壳稳定性评价结果,为京张高速铁路、云顶滑雪场、石京龙滑雪场的建设和运营提出相关建议,为京张地区国土规划提供了基础依据。   相似文献