柴达木北缘超高压变质带中的岛弧火山岩   总被引：45，自引：3，他引：45       下载免费PDF全文

史仁灯  杨经绥  吴才来  Tsuyoshi IIZUKA  Takafumi HIRATA 《地质学报》2004,78(1):52-64

青藏高原北部柴北缘发育一套与超高压变质带并行的早古生代岛弧火山岩带,岛弧火山岩以玄武岩类为主,包括一些中酸性岩类,岩石以普遍遭受绿片岩相蚀变为特征,区别于该地区普遍遭受角闪岩相区域变质的元古代的基性火山岩。该早古生代的岛孤火山岩显示三组地球化学特征:①VTG-Ⅰ,岛弧拉斑玄武岩(IAT);②VTG-Ⅱ,高Al次钙碱性-碱性过渡型玄武岩;③VTG-Ⅲ,较N-MORB更亏损的拉斑玄武岩(异常MORB)。研究认为前两组火山岩是成熟岛弧两个发育阶段的特征性产物:洋壳俯冲到陆壳的初用,由俯冲洋壳和地幔楔的部分熔融形成岛弧拉斑玄武岩(IAT),随着俯冲板块的速度加快和岛弧周围地壳的加厚,则形成钙碱性玄武岩(CA)、高Al玄武岩。第三组火山岩形成于弧间盆地,由亏损的地幔楔高度部分熔融形成比N-MORB亏损的的火山岩(异常MORB)。岛弧火山岩的锆石LA-ICP-MS法U-Pb年龄为514.2±8.5 Ma,说明柴北缘在早古生代发生过洋壳向陆壳的俯冲作用。鉴于该地区代表陆-陆俯冲作用的柴北缘超高压变质岩石也是形成于早古生代(494Ma),认为陆-陆俯冲作用发生在洋-陆俯冲作用之后,二者时间和空间相伴随。  相似文献   

The Present Space-Time Motion and Deformation Features of the Northeastern Margin of the Qinghai-Xizang（Tibet） Block and Its Adjacent Area     

Zhang Xiaoliang 《中国地震研究》2004,18(2):161-170

On the basis of Discontinuous Deformation Analysis (DDA), and considering the moderate intrusion of specific block boundaries to different extents, the first-order block motion model is established for the northeastern margin of Qinghai-Xizang(Tibet) block and the kinematical model for depicting deformation of small regions as well by using GPS observations of three periods (1991, 1999 and 2001). By simulating, we obtained the motion features of the firstorder blocks between the large WWN faults on the sides of the studied region, the distribution features of the principal strain rate field and the inhomogeneous motion features with spacetime of the faults in the northern boundary of the Qinghai-Xizang (Tibet) block.  相似文献   

The Activity of Major Faults and the Hydrothermal Alteration Zone at Tianchi Volcano of Changbaishan     

Liu Mingjun 《中国地震研究》2004,18(3):253-262

It is found by field investigation that the near horizontal top surface of the brown or brick-red hydrothermai alteration zone varies obviously in elevation at different sections of the same layer on the caldera‘s inner wall of Tianchi, with that at the north section near the Tianwen Peak about 110 m higher than that at the south near the Jiangjun Peak in Korea. The top surface of the hydrothermai alteration zone can be taken as key horizon to tectonic movement. The difference indicates that the total uplift height of the NW wall of the Liudaogou-Tianchi-Jingfengshan fault, the principal fault trending NE at Tianchi, is bigger than that of the SE wall ever since the occurrence of hydrothermal alteration. This also explains why the topography in the northwest side of Tianchi is steeper and with more developed river system than in the southeast. The uplifting of the northeastern wall is bigger than that of the southwest along the principal NW-trend fault, namely, the Baishanzhen-Tianchi-Jince fault. It is observed from characters of hydrothermal alteration and the palaeoresiduum, that the recent vertical movement rate along the principal NE-trend fault is larger than that of the principal NW-trend fault. The two faults intersect at Tianchi, dividing the volcano into 4 blocks, with the uplift magnitudes decreasing successively in the order of the north, the west, the east and the south block. The biggest uplift of the north block corresponds well to the shallow magma batch in the north of Tianchi observed by DSS and telluric electromagnetic sounding, and etc. and they may be related with the causes.  相似文献   

The Rotational Structure along the Eastern Segment of the Altyn Tagh Fault and Its Implications in Dynamics     

Wang Ping 《中国地震研究》2004,18(4):327-336

As a result of the left-lateral strike-slipping of the Altyn Tagh fault in Neotectonic period, a contra-rotational structure, namely the Zhaobishan vortex structure, has developed at the juncture of the main Altyn Tagh fault and the northern fringe fault of the Qilian Mountains.Preliminary analysis on the deformation and evolution of the Zhaobishan vortex structure. In combination with the previous data, suggests that the tectonic transform between the Altyn Tagh fault and the northern fringe fault of the Qilian Mountains attributes to the deformation of the rotational structure. The existence of a series of rotational structures along the Altyn Tagh fault and on the northeastern edge of the Qinghai-Xizang(Tibet) plateau indicate that as the substance in the northern Qinghal-Xizang (Tibet) plateau moves clockwise around the eastern tectonic knot of the Himalayas, rotational structures become the principal mode on the northern marginal zone of the Plateau of transforming and absorbing tectonic deformation.  相似文献   

西藏冈底斯西段狮多地区火山岩的地质地球化学特征   总被引：1，自引：4，他引：1  

黄圭成  李志昌  邱瑞照  蔡志勇 《现代地质》2004,18(4):511-517

西藏冈底斯西段狮多地区火山岩为一套高钾钙碱性和钙碱性系列岩石,分为古新世(59 7Ma)和中新世(17 2Ma)两个活动时期,早期的时代和层位大致相当于冈底斯东段的林子宗群典中组。与典中组火山岩相比较,该期火山岩的稀土元素总量(w(∑REE)=58 83×10-6)低得多,轻、重稀土分馏程度(w(La)N/w(Yb)N=3 44)较弱,分布曲线更为平缓;N(143Nd)/N(144Nd)的现在值(0 512275～0 512420)和初始值εNd(t)(-6 7～-4 0)也明显偏低,这反映冈底斯东、西段同一时期的火山活动及演化各具特色。根据Pb、Nd、Sr同位素的组成特征和微量元素构造环境判别推断,狮多地区火山岩形成于陆缘弧—陆 陆碰撞造山的发展演化环境,是新特提斯洋壳向大陆下俯冲作用过渡到陆 陆碰撞造山作用的产物。狮多铁 铜矿与古新世火山岩有成因联系。  相似文献   

内蒙古"宝音图隆起"的归属讨论   总被引：5，自引：0，他引：5  

沈存利  陈志勇  常忠耀 《华北地质》2004,27(1):18-23

对比研究表明，内蒙古“宝音图隆起”和狼山地区的古元古代宝音图岩群与新太古代色尔腾山岩群都是由中低级变质的各种片岩、大理岩组成，一致的岩石组合和变质相暗示二者可能是等同物而不是两个岩群。以物探资料为据的构造研究也证实，“宝音图隆起”与狼山地区之间并无槽一台级的大型断裂构造分开，二者实为统一的构造整体而不是分属槽台，只因两侧被两条近于平行的NE向断裂围限，使其总构造线方向呈NE或NNE向而与色尔腾山的构造线不同。结论认为，“宝音图隆起”仍是华北陆块的一部分，不属于内蒙古一大兴安蛉地槽褶皱系。  相似文献   

南秦岭十里坪锑矿床成矿时代及成因的初步研究   总被引：1，自引：1，他引：1  

谢才富  熊成云  胡宁  李六权  常海亮  李劲松  管魁敏 《矿床地质》2004,23(4):473-483

十里坪锑矿床受赵川陆缘隆_滑构造的主滑脱拆离带的控制。矿体呈脉状赋存于韧_脆性主滑脱带上部的脆性次级断层_节理中,矿石类型主要为萤石石英辉锑矿型。围岩为太古宙_元古宙变质岩系,围岩蚀变弱。成矿流体属H2O_CO2_NaCl体系,流体包裹体盐度w(NaCleq)为3.6%～11.3%,均一温度为109～232℃,形成压力大致为800×105Pa。硫、铅同位素研究表明,矿质主要来源于变火山岩围岩;氢、氧同位素显示,成矿流体以大气降水为主,初步将该矿床定为变质岩源就地式大气降水热液矿床。矿石中萤石Sm_Nd等时线年龄为(392±24)Ma,与南秦岭北部晚古生代拗陷区热水喷流_沉积成矿时代相一致,它们都形成于秦岭微板块泥盆纪非造山裂解阶段。  相似文献   

西藏纳木错和藏北高原古大湖晚更新世以来的湖泊演化与气候变迁   总被引：10，自引：5，他引：10       下载免费PDF全文

朱大岗孟宪刚  赵希涛邵兆刚杨朝斌  马志邦吴中海 王建平 《中国地质》2004,31(3):269-277

根据野外水准测量与室内实验分析，本文探讨了西藏纳木错和藏北高原古大湖晚更新世以来的湖泊演化和气候变迁。在纳木错沿岸拔湖48m以下，发育了6级湖岸阶地，拔湖48-139．2m发育有高位湖相沉积。研究表明，纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段：①116-37ka B．P．间的古大湖期；②37-30ka B．P．间的外流湖期；③30kaB．P．以来的纳木错期。在古大湖阶段，包括纳木错、色林错和扎日南木错、当惹雍错等藏北高原东南部的一大批现代大、中、小型湖泊，都是互相连通的一个古大湖，其范围可能超过了现代的藏北内、外流(怒江)水系的分水岭。它或许还与藏北高原南部和西部的其他古湖相连，成为统一的藏北高原“古大湖”。通过对纳木错湖相沉积形成时代与深海氧同位素对比，易溶盐、pH值、地球化学、介形类和孢粉分析等的综合研究发现，湖相沉积记录了自晚更新世以来的湖泊演化和气候变迁信息。资料显示古大湖期湖面最高，气候温和清爽；外流湖期湖面急剧下降，气温和湿度较现今略高；纳木错期以来气候经历了全新世最宜期的暖湿后日益干旱化，气温波动，湖面持续下降。表明自晚更新世以来该区气候在逐渐变干的总趋势的基础上，经历了多次明显的冷暖与干湿波动。  相似文献   

扬子克拉通周边及其隆起边缘的铅锌矿床   总被引：30，自引：7，他引：30       下载免费PDF全文

芮宗瑶叶锦华  张立生王龙生 梅燕雄 《中国地质》2004,31(4):337-346

扬子准地台为大型克拉通碳酸盐发育的地区，从震旦系到中三叠统为典型盖层沉积，其中许多地层中不乏碳酸盐沉积。新中国建国以来，在其周边及其隆起边缘的碳酸盐地层中，陆续发现了许多层控铅锌矿床。近几年来，随着地质大调查的开展，又发现一批很有希望的铅锌矿化集中区。笔者总结了这些铅锌矿床的地质特征，并将这些矿床与国外的MVT矿床进行对比，探讨它们的矿质来源、成矿溶液、成矿机制和成矿控制因素等。  相似文献   

Tectonic significance of the present relief of the Betic Cordillera     

Carlos Sanz de Galdeano  Pedro Alfaro   《Geomorphology》2004,63(3-4):175-190

Tortonian calcarenites of the Betic Cordillera were deposited in coastal or very shallow marine environments and represent an ideal marker for estimating vertical movements from the late Miocene to the Present. A map showing the heights at which these Tortonian marine rocks are situated has a clear correlation with the present relief, indicating that today's relief has been formed since the Tortonian. There is also a good correlation between present relief and the Bouguer anomaly distribution in the Betic Cordillera, as well as with crustal thickness. Likewise, the present relief is directly related to the geodynamic setting of a horizontal N–S to NNW–SSE compression and an almost perpendicular extension, along with isostatic readjustment, existing in the Betic Cordillera from the Tortonian. As a result of these regional stresses, faults and folds have produced notable vertical movements. The highest rates of uplift of the Betic Cordillera coincide with large antiforms, in particular those of the Sierra Nevada and the Sierra Filabres. Several subsiding sectors also exist (for example, the Granada Basin or the Guadalquivir Basin). The foreland Guadalquivir Basin has a complex history because the uplift in its eastern sector and subsidence in the western sector coexisted during the late Tortonian. Today the whole Betic Cordillera is characterized by differential regional uplift, even in the aforementioned subsiding sectors.  相似文献