原特提斯洋的俯冲、增生及闭合:阿尔金-祁连-柴北缘造山系早古生代增生/碰撞造山作用   总被引：20，自引：18，他引：2  

张建新  于胜尧  李云帅  喻星星  林宜慧  毛小红 《岩石学报》2015,31(12):3531-3554

分布在青藏高原北缘的阿尔金-祁连-柴北缘早古生代造山系被认为是原特提斯构造域最北部的构造拼合体。与其北侧具有长期增生历史的中亚造山系相比,特提斯造山拼合体被认为是各种来自冈瓦纳大陆北部大陆块体相互碰撞的产物。然而,与典型的阿尔卑斯和喜马拉雅碰撞造山带相比,阿尔金-祁连-柴北缘早古生代造山系包括有大量蛇绿岩、弧岩浆杂岩、俯冲-增生杂岩等,因此一些学者认为青藏高原北部的早古生代造山系为沿塔里木和华北克拉通边界向南逐渐增生的增生型造山带。但是,增生造山模式又很难解释南阿尔金-柴北缘地区普遍存在的与大陆俯冲有关的UHP变质岩、广泛分布的巴罗式变质作用和相关的岩浆作用,以及与碰撞造山有关的变形构造等。在本文中,通过对已有研究资料的综合总结,结合一些新的研究资料,我们提出在青藏高原东北缘的阿尔金-祁连-柴北缘造山系中,早古生代时期存在两种不同类型的造山作用,即增生和碰撞造山作用,其主要标志是北祁连-北阿尔金的HP/LT变质带、蛇绿混杂岩及与洋壳俯冲有关的构造岩浆作用,以及分布在柴北缘-南阿尔金与大陆俯冲和陆陆碰撞有关的UHP变质带、区域巴罗式变质作用、深熔作用、相关的岩浆活动及伸展垮塌作用等,并建立了一个反映原特提斯洋俯冲、增生、闭合及碰撞造山作用的构造模式。  相似文献   

荷叶塘陨石:一个L3型普通球粒陨石的岩石学和地球化学特征     

王桂琴  缪秉魁  林杨挺 《岩石学报》2015,31(9):2724-2736

荷叶塘为一块我国降落的原始3型普通球粒陨石,因此具有重要研究意义。本文对荷叶塘陨石光薄片及粉末样品的岩石学、矿物学和全岩组成地球化学特征进行研究,为这块陨石的深入研究提供重要基础数据。研究表明荷叶塘陨石具L3型陨石岩石学特征,具典型的球粒陨石结构,球粒清晰,球粒结构类型多,基质重结晶程度低,组成模式为:球粒80vol%,金属和硫化物含量为5vol%,基质15vol%。矿物化学成分表明,该陨石球粒以Ⅰ型(贫铁型)球粒为主,橄榄石Fa0.41-34.1(PMD=51),低钙辉石Fs1.82-27.2(PMD=88),Wo0.18-3.13(PMD=103),铁纹石中Co含量平均0.62%(PMD=20),矿物成份不均一程度高,橄榄石矿物结晶颗粒内部化学成分变化大,呈正环带分布,与岩浆型结晶顺序一致,球粒与基质及间隙物成分明显不同,表现为不同物质来源。化学成分全岩分析结果显示,荷叶塘陨石亲石、亲铁元素含量均为L型陨石特征。依据以上岩石矿物学和化学组成特征,依照陨石亚分类参数,将其类型划分为L3.4型普通球粒陨石。冲击变质程度S2,风化程度W1。研究结果表明荷叶塘陨石为一块受后期水、热蚀变和风化影响较少的原始类型陨石。组成矿物成分极不均一,在矿物晶体内部,球粒内部及球粒与基质间均有明显变化。  相似文献   

非火山地热区玛旁雍热田土壤CO_2脱气研究          下载免费PDF全文

肖琼  王鹏  沈立成薛 梅 《中国地质》2015,(6):2019-2019

地热活动是地球脱气的重要形式之一,其过程常伴随大量温室气体排放。选取非火山地热区西藏玛旁雍热田作为研究对象,基于菲克扩散定律对地热田区土壤CO_2脱气量进行评估。结果表明:该区一般土壤CO_2脱气通量为0.167~0.771 kg/(m2·a),含喷气孔区域土壤CO_2脱气通量为2.054~7.877 kg/(m2·a),含喷气孔地区的土壤CO_2脱气通量是一般土壤脱气量的18.9倍;与全球火山区土壤脱气量(0.001~2.25 Mt/(m2·a))相比,其值显著偏低;但比青藏高原高寒草原生态系统土壤的CO_2排放量(187.46 g/(m2·a))大。结合区域地质背景推测地热系统中的CO_2含量主要来源于岩浆脱气和热液同长石等围岩矿物的蚀变反应。区内土壤CO_2的低脱气通量受透水性较差的碎屑岩沉积盖层约束。  相似文献   

拉萨地块松多榴辉岩的变质演化过程:NCKMnFMASHTO体系中的相平衡关系   总被引：2，自引：0，他引：2       下载免费PDF全文

黄杰  田作林张 聪杨经绥陈 梅 《中国地质》2015,(5):1559-1571

拉萨地块松多榴辉岩主要矿物组合为石榴子石、绿辉石、角闪石、多硅白云母、绿帘石、金红石。石榴子石环带不明显,核部成分均一,从核部到边部,镁铝榴石和钙铝榴石含量降低,可能分别记录了榴辉岩峰期及退变质过程信息。绿辉石显示微弱的成分环带,硬玉含量从核部到边部略有升高,部分绿辉石边部发育韭闪石退变质边,反映了在减压过程中外来流体进入体系的过程。多硅白云母具有高的Si含量(3.5~3.6),其中石榴石包体中的多硅白云母相对基质中的白云母有更高的Si值。本文利用Thermocalc变质相平衡模拟软件,结合详细岩相学观察,在NCKMn FMASHTO体系下,模拟松多含多硅白云母榴辉岩的变质演化过程。其中,榴辉岩峰期矿物组合为g+o+law+phn+ru,石榴石核部最大镁铝榴石值和石榴子石包体中多硅白云母最大Si值确定的榴辉岩峰期温压条件约为620℃,32×105Pa,榴辉岩经历了近等温降压的退变质过程。相平衡模拟结果表明拉萨地块松多榴辉岩经历了超高压变质作用过程,并经历了相对快速的折返过程到中部地壳层次。  相似文献   

锚拉抗滑桩及锚喷技术联合应用于快速滑动的滑坡防护加固工程          下载免费PDF全文

林思波 《探矿工程》2015,42(5):62-66

以桂林—阳朔高速公路K2542+750～810上边坡滑坡防护治理工程为例,介绍了锚拉抗滑桩及锚喷技术联合应用于治理快速滑动的滑坡的应用情况。滑坡体主要由断层破碎带岩土组成,具有地质构造复杂、岩石破碎、残坡积土孔隙大、雨季地下水丰富、滑坡体岩石成分复杂、力学性能差异大、正处于快速滑移阶段等特点;在滑坡防护加固工程的设计和施工中采用该技术方法等综合措施,解决了突出的问题,并取得了良好的经济效益和社会效果。  相似文献   

双重含水介质水文地质参数的高分辨率识别     

何林青  黄琨  万军伟  何怡  梅伟标  武鑫 《地质科技情报》2015,(1):216-220

某火山岩矿区由于受后期构造影响,含水介质除了发育成岩裂隙-孔洞外,还发育有多组构造裂隙和剪切破碎带。抽水试验显示:抽水早期(≤6min)各观测孔的降深明显大于泰斯理论降深(单重均质),中后期(6min)趋于一致,呈现出双重含水介质的释水特征。本次研究在充分分析双重介质释水机理的基础上,结合时间步长为20s的高分辨率降深资料,采用分段泰斯模型进行了水文地质参数的识别。结果表明:剪切破碎带等强导水介质的弹性给水度略小于成岩裂隙-孔洞弱导水介质的弹性给水度;但导水系数相差很大,强导水介质一般为5 590~6 130m2/d,而弱导水介质仅715~743m2/d,这必然会导致未来矿山开拓过程中初见涌水量和稳定涌水量的显著差异,需要引起足够的重视。  相似文献   

Compositions and Pressure–Temperature Conditions of Metamorphic Fluids Overprinting the Talate VMS Pb–Zn Deposit, Southern Altay, China     

ZHANG Hui  XU Jiuhu  CHENG Xihui  GUO Xuji  LIN Longhu  YANG Rui  BIAN Chunjing 《《地质学报》英文版》2015,89(3):794-810

The Talate Pb-Zn deposit,located in the east of the NW-SE extending Devonian Kelan volcanic-sedimentary basin of the southern Altaides,occurs in the metamorphic rock series of the upper second lithological section of the lower Devonian lower Kangbutiebao Formation(D_1k_1~2).The Pb-Zn orebodies are stratiform and overprinted by late sulfide—quartz veins.Two distinct mineralization periods were identified:a submarine volcanic sedimentary exhalation period and a metamorphic hydrothermal mineralization period.The metamorphic overprinting period can be further divided into two stages:an early stage characterized by bedding-parallel lentoid quartz veins developed in the chlorite schist and leptite of the ore-bearing horizon,and a late stage represented by pyritechalcopyrite-quartz veins crosscutting chlorite schist and leptite or the massive Pb-Zn ores.Fluid inclusions in the early metamorphic quartz veins are mainly CO_2-H_2O-NaCI and carbonic(CO_2±CH_4±N_2) inclusions with minor aqueous inclusions.The CO_2-H_2O-NaCl inclusions have homogenization temperatures of 294-368℃,T_(m,CO2) of-62.6 to-60.5℃,T_(h,CO2) of 7.7 to 29.6℃(homogenized into liquid),and salinities of 5.5-7.4 wt%NaCl eqv.The carbonic inclusions have T_(m,CO2)of-60.1 to-58.5℃,and T_(h,Co2) of-4.2 to 20.6℃.Fluid inclusions in late sulfide quartz veins are also dominated by CO_2-H_2O-NaCl and CO_2±CH_4 inclusions.The CO_2-H_2O-NaCl inclusions have T_(b,tot) of142 to 360℃,T_(m,CO2)of-66.0 to-56.6℃,T_(h,CO2) of-6.0 to 29.4℃(homogenized into liquid) and salinities of 2.4-16.5 wt%NaCl eqv.The carbonic inclusions have T_(m,Co2)of-61.5 to-57.3℃,and T_(h,CO2) of-27.0to 28.7℃.The aqueous inclusions(L-V) have T_(m,ice) of-9.8 to-1.3℃ and T_(h,tot) of 205 to 412℃.The P-T trapping conditions of CO_2-rich fluid inclusions(100-370 MPa,250-368℃) are comparable with the late- to post-regional metamorphism conditions.The CO_2-rich fluids,possibly derived from regional metamorphism,were involved in the reworking and metal enrichment of the primary ores.Based on these results,the Talate Pb-Zn deposit is classified as a VMS deposit modified by metamorphic fluids.The massive Pb-Zn ores with banded and breccia structures were developed in the early period of submarine volcanic sedimentary exhalation associated with an extensional subduction-related back-arc basin,and the quartz veins bearing polymetallic sulfides were formed in the late period of metamorphic hydrothermal superimposition related to the Permian-Triassic continental collision.  相似文献   

Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems   总被引：1，自引：0，他引：1  

ZHANG Lan  YANG Jingsui  Paul T. ROBINSON  XIONG Fahui  CHEN Yanhong  LAI Shengmin  CHEN Mei 《《地质学报》英文版》2015,89(2):402-417

Listwanite from the Luobusa ophiolite,Tibet,forms a narrow,discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. Three alteration zones characterized by distinct mineral components and texture are recognized and,in order of increasing degree of alteration,these are: zoneIII is rich in serpentine minerals; zoneII is rich in talc and carbonates; and zoneI is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith,although some oxides show linear correlations with Mg O. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zoneI and zoneIIand is up to 0.91 g/t in one sample from zoneI. We show that CO2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains,indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. The compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.  相似文献   

Unlocking Key Factors of Shale Play Sweet Spotting Appraisal - Field Case Studies From China and North America     

YANG Zhi  ZOU Caineng  HOU Lianhu  CUI Jingwei  WU Songtao  LIN Senhu 《《地质学报》英文版》2015,89(Z1):293-293

<正>This study proposes the controlling factors of shale play sweet spotting under different maturation stages and various hydrocarbon composition in China and North America,including some typical examples with best practices,such as the Silurian Longmaxi shale gas in Sichuan Basin in Southwestern China,the Triassic Yanchang liquid-rich oil in Ordos Basin in North-central  相似文献   

Improved Geometric Model of Extensional Fault–bend Folding     

ZHENG Xiaoli  HE Guangyu  HU Senqing  YAO Zewei  WANG Hui  LIN Lu 《《地质学报》英文版》2015,89(6):1847-1857

Extensional fault–bend folds, also called rollovers, are one of the most common structures in extensional settings. Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls. However, the oblique simple shear has a rather serious issue derived from the shear direction, particularly above convex bends. We use geometric and experimental methods to study the deformation of extensional fault–bend folds on convex bends. The results indicate that whether the fault bends are concave or convex, the shear direction of the hanging wall dips toward the main fault. On this basis, we improve the previous geometric model by changing the shear direction above the convex bends. To illustrate basin history, our model highlights the importance of the outer limit of folding instead of the growth axial. Moreover, we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall. This model is validated by modeling a natural structure of the East China Sea Basin.  相似文献