燕山地区宣龙坳陷中元古界洪水庄组-铁岭组沉积相分析与层序格架的建立   总被引：1，自引：0，他引：1  

霍勇  罗顺社  张建坤  庞秋维  金姗姗  尚飞 《地质科技情报》2012,31(3):8-15

根据野外露头信息的综合分析,结合沉积模式和层序地层学的基本原理,总结了燕山地区宣龙坳陷洪水庄组和铁岭组的沉积相特征和层序地层格架.研究表明,该区洪水庄组-铁岭组沉积时期为一套局限台地潮坪相沉积,垂向上的沉积微相更能敏锐地反映海平面的相对变化.根据对各个层序界面的识别,将洪水庄组划分为1个三级层序DS1,铁岭组划分为2个三级层序DS2和DS3,由海侵体系域(TST)和高位体系域(HST)组成,不具有形成凝缩层的环境.根据研究区各时期沉积环境与层序地层的特点,建立了符合研究区洪水庄组和铁岭组的沉积模式,初步探讨了研究区所经历的沉积演化过程.  相似文献   

燕山板内造山带中部“承德逆冲构造”的褶皱相关断裂构造模型   总被引：2，自引：0，他引：2       下载免费PDF全文

张长厚  邓洪菱  李程明  刘孜  邓洪旦  滕飞 《地学前缘》2012,19(5):27-40

燕山板内造山带中部承德盆地复杂的中生代褶皱及逆冲断裂构造,曾被解释为土城子组沉积之后大型逆冲推覆构造(位移量大于40～45km)又经褶皱变形的结果。近年来,土城子组沉积相和物源区分析、中新元古界沉积古地理研究以及相关构造变形研究结果等,对这一变形大型逆冲构造模型提出了多方位质疑。但已有研究并未提出新的构造模型来解释这一复杂构造区域中生代构造变形样式和形成机制。文中通过对承德盆地区域主体构造——承德向斜、向斜两翼逆冲构造变形几何学与运动学特征、向斜转折端附近构造变形与断裂发育状况进行详细野外调查及对关键地质体同位素地质年代进行测试,发现承德向斜两翼逆冲断层为分别向向斜核部以外区域逆冲的独立逆冲断层,逆冲断层活动与承德向斜变形是在统一的收缩变形体制下准同时形成的。它们形成于土城子组之后、张家口组火山活动之前,即距今约139～136 Ma。据此提出了"承德逆冲构造"的背离向斜逆冲构造模型。这一模型合理地解释了燕山中部承德盆地区域中生代构造变形和相应的盆地充填特征,同时表明,燕山板内造山带并不存在碰撞造山带前陆褶皱逆冲带中常见的大型薄皮逆冲构造样式。这一研究结果展示了褶皱相关断裂构造模型在研究和揭示收缩构造变形区域大尺度褶皱与断裂构造相互关系及准确重建区域构造演化过程方面的重要意义。  相似文献   

赣西北新元古代修水组和马涧桥组SHRIMP锆石U-Pb年龄   总被引：11，自引：1，他引：10  

高林志  黄志忠  丁孝忠  刘燕学  庞建峰  张传恒 《地质通报》2012,31(7):1086-1093

依据精确地测得的修水组凝灰岩SHRIMP锆石U-Pb年龄(824Ma±5Ma,MSWD=1.3),将修水组明确定位于双桥山群的最上部。结合"江南造山带"锆石U-Pb年龄:东部变质基底双桥山群,西部变质基底梵净山群、似盖层下江群和中部变质基底冷家溪群、似盖层板溪群的锆石SHRIMP U-Pb年龄,将双桥山群上部修水组明确地定位于"武陵运动"之下的新元古代地层。同时,首次在上覆地层马涧桥组火山凝灰碎屑岩中获得3组锆石U-Pb年龄,其中一组继承锆石(824Ma±5Ma,MSWD=1.9),反映了修水组被隆起和剥蚀的证据;而最年轻的一组锆石反映了沉积同时代的凝灰岩年龄为(769Ma±8Ma,MSWD=0.55)。依据该年龄数据,将马涧桥组明确定位于板溪期沉积地层。该年龄对限定区域地层对比和构造演化都有重要意义。上述锆石U-Pb年龄标示了赣西北地区同样存在820Ma界面上下的新元古代地层,为江南古陆变质地层的对比提供了新的年代学数据。  相似文献   

Neoproterozoic bimodal volcanic rocks and granites in the western Dabie area,northern margin of Yangtze block,China: implications for extension during the break-up of Rodinia     

《International Geology Review》2012,54(11):1370-1390

ABSTRACT

To better understand the Neoproterozoic tectonic evolution along the northern margin of Yangtze Block, we have determined the geochronological and geochemical compositions of newly recognized bimodal volcanic suite and coeval granites from the western Dabie terrain. LA-ICP-MS zircon U-Pb dating reveals that the felsic and mafic volcanics from the Hong’an unit have crystallization ages of 730 ± 4Ma and 735 ± 5Ma, respectively, indicating that the bimodal suite was erupted during the Neoproterozoic. The Xuantan, Xiaoluoshan, and Wuchenhe granites yield U-Pb ages of 742 ± 4 Ma, 738 ± 4 Ma, and 736 ± 4 Ma, respectively. The felsic volcanic rocks show peraluminous characteristics, and have a close affinity to S-type granite. The mafic volcanic rocks are basalt in compositions, and are likely generated from a depleted mantle source. The granites belong to high-K calc-alkaline and calc-alkaline series, display metaluminous to peraluminous, and are mainly highly fractionated I-type and A-type granite. The granites and felsic volcanics have zircon εHf(t) values of ?16.4 to + 5.6 and two-stage Hf model ages (T_DM2) of 1.28 to 2.40 Ga, suggesting that they were partial melting of varying Mesoproterozoic–early-Neoproterozoic crust. The granites have εNd_(t) of -14.7 to -1.5, and the two-stage Nd model ages (T_DM2) values of 1.54 to 2.61 Ga, also implying the Yangtze crustal contribution. These Neoproterozoic bimodal suite and coeval granites were most likely generated in a rifting extensional setting, triggered by the mantle upwelling, associated with crust–mantle interaction. Intensive magmatic rocks are widespread throughout the South Qingling, Suizhao, western Dabie and eastern Dabie areas during 810–720 Ma, and show peak ages at ~ 740 Ma. Combining regional geology, we support a continental rifting extensional setting for the north margin of the Yangtze Block during the break-up of the supercontinent Rodinia.  相似文献   

东昆仑水闸东沟-黄龙沟金矿床硫化物矿物学特征对可见金形成条件的制约   总被引：2，自引：1，他引：1  

张金阳  马昌前  李建威 《矿床地质》2012,31(6):1184-1194

东昆仑五龙沟地区水闸东沟-黄龙沟金矿床处于昆中断裂北部,受NW向构造控制,矿区出露中元古界小庙组和新元古界丘吉东沟组地层,岩浆岩以早古生代和早中生代侵入岩为主。围岩蚀变以绢云母化和硅化为主,矿体严格受NW向剪切带控制,赋矿岩石为早古生代正长花岗岩和新元古代丘吉东沟组板岩。综合野外地质特征、矿相学观察和电子探针测试结果,水闸东沟-黄龙沟金矿床可划分出4个成矿期:沉积期、热液Ⅰ期、热液Ⅱ期和表生期。新元古代沉积期属金的初步富集期;早古生代热液Ⅰ期可分为4个阶段,其中第一阶段(磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段)是金的主成矿阶段;早中生代热液Ⅱ期金再次活化富集;表生期代表矿体暴露地表后的变化。热液Ⅰ期的磁黄铁矿-毒砂-斜方砷铁矿-自然金阶段,由早至晚体系温度和硫逸度升高,代表前进变质作用,变质条件达绿片岩相上限。斜方砷铁矿交代毒砂的结构中通常可以观察到可见金,说明该阶段是由不可见金向可见金转化的重要时期,可见金形成于绿片岩相上限的温度范围内。  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111001113   总被引：1，自引：0，他引：1  

R. Damian Nance  Gabriel Guti errez-Alonso  J. Duncan Keppie  Ulf Linnemann  J. Brendan Murphy  Cecilio Quesa  Rob A. Strachan  Nigel H. Woodcock 《地学前缘(英文版)》2012,3(2):125-135

The Rheic Ocean was one of the most important oceans of the Paleozoic Era.It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita-Alleghanian -Variscan orogen during the assembly of Pangea.Rifting began in the Cambrian as a continuation of Neoproterozoic orogenic activity and the ocean opened in the Early Ordovician with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana along the line of a former suture.The rapid rate of ocean opening suggests it was driven by slab pull in the outboard lapetus Ocean.The ocean reached its greatest width with the closure of lapetus and the accretion of the periGondwanan arc terranes to Laurentia in the Silurian.Ocean closure began in the Devonian and continued through the Mississippian as Gondwana sutured to Laurussia to form Pangea.The ocean consequently plays a dominant role in the Appalachian-Ouachita orogeny of North America,in the basement geology of southern Europe,and in the Paleozoic sedimentary,structural and tectonothermal record from Middle America to the Middle East.Its closure brought the Paleozoic Era to an end.  相似文献   

Magnetotelluric Constraints on the Occurrence of Lower Crustal Earthquakes in the Intra-plate Setting of Central Indian Tectonic Zone     

K. K. ABDUL AZEEZ 《《地质学报》英文版》2016,90(3):884-899

Lower crustal earthquake occurrence in the Central Indian Tectonic Zone(CITZ) of the Indian sub-continent was investigated using magnetotelluric(MT) data. MT models across the CITZ, including the new resistivity model across the 1938 Satpura lower crustal earthquake epicenter, show low resistive(80 ?m) mid-lower crust and infer small volume(1 vol%) of aqueous fluids existing in most part of lower crust. This in conjunction with xenoliths and other geophysical data supports a predominant brittle/semi-brittle lower crustal rheology. However, the local deep crustal zones with higher fluid content of 2.2%–6.5% which have been mapped imply high pore pressure conditions. The observation above and the significant strain rate in the region provide favorable conditions(strong/moderate rock strength, moderate temperature, high pore pressure and high strain rate) for brittle failure in the lower crust. It can be inferred that the fluid-rich pockets in the mid-lower crust might have catalyzed earthquake generation by acting as the source of local stress(fluid pressure), which together with the regional stress produced critical seismogenic stress conditions. Alternatively, fluids reduce the shear strength of the rocks to favor tectonic stress concentration that can be transferred to seismogenic faults to trigger earthquakes.  相似文献   

马尼干戈盆地河流阶地特征及其构造成因     

谭亮  夏月成  江仁剑  龚彬  葛俊杰  马昌威 《四川地质学报》2014,(4):484-488

马尼干戈第四系盆地河流阶地具有"砾石分选、磨圆差,分层结构不明显"的物质组成、"沿玉曲河南岸单侧发育、具菱形状阶地"的分布和形态及"第Ⅲ级阶地因次第升降而裂解"的构造特征等。因此推断马尼干戈盆地可能是区域上三大构造单元—"南部义敦群域辗掩系统(义敦岛弧带)、中部结合群域原地系统(甘孜-理塘结合带北段)和北部西康群域辗掩系统(西康群)"晚近期不均衡抬升(块断升降)引起局部断陷成盆、并叠加左行走滑拉分而形成的。这一发现对松潘-甘孜造山带第四纪新构造期活动的研究具有重要意义。  相似文献   

Rapid cooling of the Yanshan Belt,northern China: Constraints from 40Ar/39Ar thermochronology and implications for cratonic lithospheric thinning     

《Journal of Asian Earth Sciences》2014

The Yanshan Orogenic Belt is located in the northern part of the North China Craton (NCC), which lost ∼120 km of lithospheric mantle during Phanerozoic tectonic reactivation. Mesozoic magmatism in the Yanshan fold-and-thrust belt began at 195–185 Ma (Early Jurassic), with most of the granitic plutons being Cretaceous in age (138–113 Ma). Along with this magmatism, multi-phase deformational structures, including multiple generations of folds, thrust and reverse faults, extensional faults, and strike-slip faults are present in this belt. Previous investigations have mostly focused on geochemical and isotopic studies of these magmatic rocks, but not on the thermal history of the Mesozoic plutons. We have applied ⁴⁰Ar/³⁹Ar thermochronology to biotites and K-feldspars from several Lower Cretaceous granitic plutons to decipher the cooling and uplift history of the Yanshan region. The biotite ⁴⁰Ar/³⁹Ar ages of these plutons range from 107 to 123 Ma, indicating that they cooled through about 350 °C at that time. All the K-feldspar step-heating results modeled using multiple diffusion domain theory yield similarly rapid cooling trends, although beginning at different times. Two rapid cooling phases have been identified at ca. 120–105 and 100–90 Ma. The first phase of rapid cooling occurred synchronously with widespread extensional deformation characterized by the formation of metamorphic core complexes, A-type magmatism, large-scale normal faults, and the development of half-graben basins. This suggests rapid exhumation took place in an extensional regime and was a shallow-crustal-level response to lithospheric thinning of the NCC. The second phase of rapid cooling was probably related to the regional uplift and unroofing of the Yanshan Belt, which is consistent with the lack of Upper Cretaceous sediments in most of the Yanshan region.  相似文献   

Uplift-denudation history of the Qinling orogen: Constrained from the detrital-zircon U–Pb geochronology     

《Journal of Asian Earth Sciences》2014

This paper presents a great number of detrital zircon U–Pb ages from the Middle Triassic to the Middle Jurassic sediments in the Jiyuan basin, southern North China. The results represent age spectra from 2.9 Ga to 216 Ma, with five peaks at 2.5 Ga, 1.9 Ga, 840 Ma, 440 Ma, and 270 Ma and two grains of ∼220 Ma. The ages of 2.5 Ga and 1.9 Ga are mainly derived from the Precambrian basement of the North China Block, whereas the others are typical characteristics of the Qinling orogenic belt. An important observation is that the Qinling-sourced detrital zircons become older as the strata get younger. Samples from the Middle Triassic to early Late Triassic strata are characterized by the age peak at 270 Ma, whereas the Late Late Triassic to Early Middle Jurassic samples are dominated by age peaks at 840 Ma and 440 Ma and minor grains within 800–650 Ma. Two grains of ∼220 Ma are preserved in the Late Middle Jurassic sample, which may be contributed by the Carnian deep plutons. These signatures indicate that the unroofing pattern of the Qinling orogenic belt developed by the denudation of materials from young covers to old basements and the Carnian deep plutons. Integrated with the data reported from the Hefei Basin, it is well-established that the intensity of unroofing increased from the Qinling to the Dabie orogen in the Early Jurassic, and the denudation timing of the ultra-high pressure (UHP) and high pressure (HP) rocks or Carnian plutons changed successively from the Early Jurassic in the Dabie to the Late Middle Jurassic in the Qinling orogen.  相似文献