Palaeomagnetism and geochronology of mafic dykes in south Siberia, Russia: the first precisely dated Early Permian palaeomagnetic pole from the Siberian craton     

S. A. Pisarevsky  D. P. Gladkochub  T. A. Donskaya  B. De Waele  A. M. Mazukabzov 《Geophysical Journal International》2006,167(2):649-658

  相似文献   

粤北下庄铀矿田黄陂-张光营辉绿岩脉的成因：元素地球化学和Nd-Sr-Pb-O同位素证据   总被引：6，自引：2，他引：6  

陆建军  吴烈勤  凌洪飞  沈渭洲  高剑峰  黄国龙  邓平  谭正中 《岩石学报》2006,22(2):397-406

黄陂-张光营辉绿岩脉位于粤北贵东复式花岗岩岩体东部的下庄铀矿田内,形成于142．6±3．0Ma。岩石化学呈现拉斑玄武宕系列的特征,富集大离子亲石元素；在蛛网图上,Th表现出正异常,而Ba呈负异常,P轻度亏损,无Nb,Ta,Zr,Hf异常；轻、重稀土之间分馏不明显,基本无Eu异常。微量元素和稀土元素特征与板内玄武岩的相似；铅同位素具有典型的Dupal异常铅特征,ε_(Nd)(t)值为3．2～4．7,(~(87)Sr/~(86)Sr),为0．70446～0．70628；在Pb-Pb,Nd-Pd,Nd-Sr和Sr-Pb相关图解上,数据点都位于亏损地幔和富集地幔Ⅱ之间。地球化学特征表明,黄陂-张光营辉绿岩脉是在拉张的构造环境下由介于亏损地幔和富集地幔Ⅱ之间的、相对富集的地幔源区部分熔融形成的,而这种富集地幔可能是由俯冲带流体交代形成的。  相似文献   

云南哀牢山金矿带大坪韧性剪切带型金矿40Ar-39Ar定年   总被引：7，自引：0，他引：7       下载免费PDF全文

孙晓明  熊德信  石贵勇  王生伟  翟伟 《地质学报》2007,81(1):88-92

云南大坪金矿是哀牢山金矿带中最重要的金矿之一,主要赋存在受到强烈韧性剪切和水-岩反应的加里东期闪长岩中,是典型的韧性剪切带控矿型金矿。本文对大坪金矿绢英岩化近矿围岩中的热液绢云母进行了40Ar-39Ar定年,得到其坪年龄为33.76±0.65Ma,相应的反等时线和正等时线年龄分别为33.55±0.74Ma和33.57±0.74Ma,显示大坪属于喜马拉雅早期金矿。这些年龄数据与哀牢山金矿带中广泛出现的喜马拉雅期煌斑岩脉年龄(33～34Ma)非常接近,显示金矿与上地幔部分熔融形成的煌斑岩之间可能存在成因上的联系。喜马拉雅早期,本区在地壳拉张和强烈韧性剪切条件下,Moho面上升,地幔物质部分熔融并上涌,形成大量煌斑岩等基性岩脉,地幔排气形成的深源地幔流体和下地壳脱水形成的富CO2流体混合,沿韧性剪切带上升,并与糜棱岩化的加里东期闪长岩围岩发生水-岩反应,局部发生流体沸腾作用,导致成矿流体物理化学条件的改变和矿石矿物的沉淀,在剪切带脆性构造中形成含金石英脉。  相似文献   

Fault-related carbonate breccia dykes in the La Chilca area,Eastern Precordillera,San Juan,Argentina     

《Journal of South American Earth Sciences》2015

Carbonate fault breccia dykes in the Cerro La Chilca area, Eastern Precordillera, west-central Argentina, provide clues on the probable mechanism of both fault movement and dyke injection.Breccia dykes intrude Upper Carboniferous sedimentary rocks and Triassic La Flecha Trachyte Formation. The timing of breccia dyke emplacement is constrained by cross cutting relationships with the uppermost Triassic unit and conformable contacts with the Early Miocene sedimentary rocks. This study supports a tectonic-hydrothermal origin for these breccia dykes; fragmentation and subsequent hydraulic injection of fluidized breccia are the more important processes in the breccia dyke development.Brecciation can be triggered by seismic activity which acts as a catalyst. The escape of fluidized material can be attributed to hydrostatic pressure and the direction of movement of the material establishes the direction of least pressure.Previous studies have shown that cross-strike structures have had an important role in the evolution of this Andean segment since at least Triassic times. These structures represent pre-existing crustal fabrics that could have controlled the emplacement of the dykes. The dykes, which are composed mostly of carbonate fault breccia, were injected upward along WNW fractures.  相似文献   

华阳川铀多金属矿床碳酸岩脉矿化特征   总被引：1，自引：0，他引：1  

惠小朝  何升 《铀矿地质》2016,(2):93-98

华阳川铀多金属矿床是小秦岭成矿带中成矿特征最为独特的矿床,其碳酸岩脉破碎带是重要的成矿空间。区内碳酸岩分布很广泛,沿NW向张性和张扭性断裂及其伴生的次级裂隙充填,呈单脉状和网脉状穿插于变质岩、伟晶岩中。矿化碳酸岩脉中,脉石矿物大部分为方解石,少量为角闪石、石英、磁铁矿、碱性长石等;矿石矿物为铌钛铀矿、独居石、褐帘石、重晶石、天青石。铌钛铀矿是最主要的赋铀矿物,矿化元素铀、铌、钡、锶、稀土等平均含量分别为2554.20×10-6、1836.80×10-6、4145.78×10-6、4412.80×10-6、7348.44×10-6,可以综合开发利用。  相似文献   

新疆哈密双井子地区空心山火山机构特征及成因机制     

彭湘萍  白云山 《地质论评》1999,45(7):1105-1110

通过野外工作,在新疆哈密双井子地区发现一空心山火山机构,以其独特地貌特征、发育环状断裂和放射状岩墙以及较规律分布的岩相特征,显示了较为典型的古火山构造。  相似文献   

湘中秋旺冲金矿区脉岩岩石学与地球化学特征及其地质意义     

周溪  彭建堂  鲁玉龙  徐军伟  谢帅  谢青 《岩石矿物学杂志》2020,39(4):441-453

对位于湘中EW向白马山-紫云山成矿带东端的秋旺冲金矿区中的脉岩进行了岩石学和地球化学研究。研究结果显示,这些脉岩主要为似斑状花岗岩、含电气石花岗岩和文象花岗岩属富硅、富碱的准铝-弱过铝质、钙碱性花岗岩,其地球化学特征表现为富集Rb、K、Th、U、Ce、Nd、Zr和Hf元素,强烈亏损Ra、Sr、P和Ti元素,稀土元素总量低,轻重稀土元素分馏均不明显,重稀土元素相对较富集,Eu负异常极为明显。通过岩石成因和构造环境判别图解结合区域上前人的研究成果,提出该区脉岩成因类型属于高分异的Ⅰ型花岗岩,是在碰撞造山后伸展构造环境中形成的。综合矿区及毗邻矿床的地质勘查资料分析,认为该区脉岩与金矿化存在空间对应关系,对金成矿有指示意义。  相似文献   

Geochronology and Geochemistry of Middle Devonian Mafic Dykes in the East Kunlun Orogenic Belt, Northern Tibet Plateau: Implications for the Transition from Prototethys to Paleotethys orogeny     

XIONG Fuhao  HUANG Weiping  MA Changqian  JIANG Hong’an  ZHOU Qin 《《地质学报》英文版》2013,87(Z1):81-81

  相似文献   

Seismic interpretation of crustal structure in the flinders‐mt lofty ranges and gulf regions,South Australia     

Ian C. F. Stewart 《Australian Journal of Earth Sciences》2013,60(3):351-362

There appears to be little correlation of earthquake epicentres with known surface geological features in South Australia. Seismic wave travel‐time residuals are used to derive corrections for the velocity and depth parameters for the simple uniform crustal model which approximates to that in South Australia. Local studies of Moho depth in the seismic zone and analysis of travel‐time station corrections from both local earthquake and teleseismic data suggest that lateral and vertical variations in the South Australian crust are small. Data presented in this paper appear to be consistent with a plate tectonic model derived from focal mechanism studies (Stewart & Mount, 1972) for the active South Australian seismic zones.  相似文献   

Timing of brittle faulting and thermal events,Sydney region: association with the early stages of extension of East Gondwana     

D. J. Och  R. Offler  H. Zwingmann  J. Braybrooke  I. T. Graham 《Australian Journal of Earth Sciences》2013,60(7):873-887

Structural studies in the Sydney region have revealed the presence of vertical to near-vertical, north-northeast-striking faults that are manifest as joint swarms and highly brecciated zones in which gouge of varying thickness is developed. Strike-slip movement accompanied by minor dip-slip, normal movement occurred on these faults. Timing of movement on these faults by K–Ar dating of illite and illite–smectite in fractions extracted from fault gouges, was attempted. These dates were compared with dates obtained from the host-rocks. K–Ar ages determined from the 2–10 μm to <0.1 μm fractions produced from the gouge and host-rocks, range from 159.5 ± 3.2 to 106.6 ± 2.1 Ma (n = 26). In <0.5 μm fractions extracted from the gouges that are less contaminated by detrital phases, K–Ar ages vary from 138 ± 4.4 to 106.5 ± 2.1 Ma (mean 121 Ma; n = 6) which are similar to ages obtained from host-rocks in the Sydney region. The similarity in age between the host rocks and gouge suggests that the K–Ar system has been reset. The resetting is attributed to a thermal event at ca 120 Ma related to the underplating of felsic intrusions associated with early stages of breakup of East Gondwana. Subsequent to this event, dykes of Early Eocene age (K–Ar whole-rock: 51.0 ± 1.1 Ma) exploited north-northeast-striking faults and subsequently developed brecciated margins. These observations and the fact that gouge formed before the thermal event suggests that movement took place on north-northeast-striking faults prior to 120 Ma and after 51 Ma.  相似文献