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1.
西藏南部绒布地区基性岩脉岩石地球化学、年代学特征及地质意义 总被引：1，自引：0，他引：1
绒布地区位于西藏南部特提斯喜马拉雅构造域中段北缘,夹持于北侧邛多江断裂和南侧的绒布-古堆断裂之间。该地区发育大量的基性岩脉。通过岩石学、年代学及岩石地球化学等方面的研究,认为区内出露的基性岩脉类型为辉绿玢岩、辉长辉绿岩及辉长岩等。辉绿玢岩结晶年龄为137. 3±1. 6Ma,具有E-MORB的特征,未遭受岩石圈地幔或地壳混染,主要形成于大洋板内环境,受洋中脊源区的影响明显。辉长辉绿岩、辉长岩结晶年龄为147. 3±3. 6Ma,与时代接近的拉康组、桑秀组基性火山岩具有相同OIB的地球化学特征,带有岩石圈地幔物质混染的痕迹,形成于强烈拉伸的大陆边缘裂谷环境。晚侏罗世-早白垩世特提斯喜马拉雅被动陆缘处于强烈拉伸、岩石圈减薄的构造背景之下,OIB型辉长辉绿岩及辉长岩与措美大火成岩省诸多OIB型基性岩具有相似岩石成因,是大陆裂谷背景下Kerguelen地幔柱与岩石圈地幔相互作用的产物;而E-MORB型辉绿玢岩则可能是靠近大陆边缘的热点以下地幔柱与软流圈地幔相互作用的产生的岩浆沿区域深大断裂运移至大陆边缘侵位的结果。OIB型辉长辉绿岩、辉长岩的结晶年龄明显早于Kerguelen地幔柱活动的峰期(132Ma),可能是地幔柱早期活动的产物; E-MORB型辉绿玢岩的存在可作为目前对于措美大火成岩省基性岩脉类型的补充,对认识措美大火成岩省具有一定的意义。 相似文献
2.
福建石狮白垩纪花岗岩与中基性脉岩的年代学与地球化学 总被引：1，自引：1，他引：0
在我国华南地区广泛发育了白垩纪岩浆活动,形成了大面积的花岗岩和多期侵位的中基性和酸性脉岩。其中中基性脉岩被认为是华南白垩纪多期伸展作用的标志之一。本文对采自福建沿海石狮地区的石狮和东埔两地的花岗岩和侵入的中基性脉岩进行了锆石U-Pb年代学和Hf同位素以及岩石元素地球化学研究。石狮地区的花岗岩和花岗闪长岩为中钾-高钾钙碱性、弱过铝质岩石,2个锆石U-Pb年龄分别为105.3±1.0Ma和105.1±0.5Ma,2个花岗岩的锆石εHf(t)为-0.9~+2.0;侵入的脉岩为辉绿岩和闪长岩,属于准铝质中钾-高钾钙碱性岩石,2个闪长岩的锆石U-Pb年龄分别89.5±1.5Ma和96.1±1.2Ma,脉岩的εHf(t)为+1.3~+5.0。石狮地区花岗岩和脉岩显示轻重稀土中等分馏和弱的Eu异常,花岗岩稀土总量明显低于脉岩,岩石大离子亲石元素富集、高场强元素亏损,显示岛弧岩浆岩的地球化学特征;微量元素判别(Ta/Hf-Th/Hf,Zr-Zr/Y)表明石狮地区的岩脉产于大陆边缘裂谷环境或板内构造环境,脉岩应是古太平洋俯冲的大陆边缘背景之上,俯冲结束后转入大陆边缘伸展作用的标志。福建沿海厦门-石狮-晋江地区的伸展作用发生在87~96Ma,与华南区域上多期伸展作用中~90Ma的伸展作用吻合。 相似文献
3.
藏南古堆地区中基性脉岩SHRIMP锆石U-Pb定年、地球化学特征及构造意义 总被引：2，自引：0，他引：2
通过对藏南隆子-古堆一带广泛发育近东西走向的中基性脉岩较系统的地质年代学和岩石地球化学研究,3个基性脉岩的SHRIMP锆石U-Pb年龄为133~140.9Ma,代表了辉长岩的结晶年龄,而中性脉岩的SHRIMP锆石U-Pb年龄130±1.7Ma代表了闪长岩的结晶年龄。表明中基性脉岩属于钙碱性-碱性系列,总体富Ti O2,平均含量为3.08,LREE富集,轻重稀土分异较为明显,LILE略为富集,HFSE亏损不明显,属被动大陆边缘构造环境,可能代表了早白垩世新特提斯洋扩张引起喜马拉雅被动大陆边缘一侧裂解的产物。 相似文献
4.
藏南特提斯喜马拉雅带内江孜-康马地区白垩纪多期基性岩浆作用 总被引：3，自引：3，他引：0
在特提斯喜马拉雅带东部江孜-康马一带发育大量近东西向展布的辉绿岩体/墙,研究表明这些基性岩至少可分为三期:(1)形成于~140Ma的辉绿岩具有OIB型地球化学特征,部分样品Sr-Nd同位素组成与其东部~132Ma错美-班布里大火成岩省中基性岩相当,部分高镁样品具有Nb-Ta负异常和Pb正异常,εNd(t)值小于0;(2)形成于~120Ma的辉绿岩显示N-MORB型地球化学特征;(3)形成于~90Ma的辉绿岩显示E-MORB型地球化学特征。后两期基性岩的Sr-Nd同位素组成均显示与印度洋MORB相关。结合同时期的Kerguelen地幔柱活动轨迹及东冈瓦纳大陆裂解事件,本文认为江孜-康马地区~140Ma基性岩代表Kerguelen地幔柱及其与上覆东冈瓦纳大陆岩石圈地幔相互作用产物,是Kerguelen地幔柱长期潜伏于东冈瓦纳大陆下的证据,在前人研究基础上将该地幔柱影响的范围从错美向西拓展了约200km;之后随着东冈瓦纳大陆裂解和印度洋的开启及扩张,印度板块逐渐北移并远离Kerguelen地幔柱,江孜-康马地区~120Ma和~90Ma两期基性岩代表新生印度洋软流圈部分熔融的产物,与Kerguelen地幔柱无关。该区识别出的三期基性岩浆活动表明:特提斯喜马拉雅带的东部在白垩纪经历了与东冈瓦纳大陆裂解、印度洋的开启和扩张相关的多期基性岩浆活动。这些基性岩为深入了解和限定特提斯喜马拉雅带自140Ma以来的古地理位置和构造演化过程提供了新的岩石记录和时间坐标。 相似文献
5.
华南新元古代中期裂谷火山岩系：Rodinia超大陆裂谷化-裂解的地质纪录 总被引：6，自引：0，他引：6
华南新元古代中期（746-827Ma）双峰式（玄武岩-流纹岩）火山岩喷发于大陆板内裂谷环境。它们极有可能与导致Rodinia超大陆裂谷化-裂解的地幔柱（或超级地幔柱）活动有关。根据岩石地球化学数据,华南新元古代中期裂谷基性熔岩可以划分为高Ti／Y（HT,Ti／Y〉500）和低Ti／Y（LT,Ti／Y〈500）两个岩浆类型。HT熔岩又可进一步划分为HT1和HT2等两个亚类。HT1熔岩主要分部于华南中-西部裂谷盆地之中,总体上属于碱性玄武质岩浆系列;HT2和LT熔岩主要分布于华南中-东部裂谷盆地之中,总体上属于拉斑玄武质岩浆系列。元素和同位素数据表明,华南新元古代中期裂谷基性熔岩的化学变化不是由一个共同的母岩浆结晶分异作用所产生。华南中-西部地区裂谷基性熔岩的母岩浆经受了辉长岩质结晶分离作用,而华南中-东部地区裂谷基性熔岩的化学演化则是受控于单斜辉石（cpx）士橄榄石（01）结晶分离作用。各个双峰式火山岩系中,基性和酸性熔岩间为分异结晶关系。华南新元古代中期裂谷火山岩系极有可能是源于共同的地幔柱,该地幔柱组分的成分为：eNd（f）≈＋6,Mg#≈0．7,La／Nb≈0．7。华南新元古代中期裂谷基性熔岩存在空间上的地球化学变化：华南中一西部HT1熔岩的母岩浆,没有受到明显的大陆岩石圈混染,保存了鲜明的地幔柱信号;而大陆地壳或大陆岩石圈混染作用对于华南中-东部LT和HT2熔岩的形成则有着重要贡献。研究揭示,华南新元古代中期裂谷基性熔岩的母岩浆总体上产生于上涌地幔柱较深层位的石榴子石稳定区（深度：100～130km）。中-西部裂谷基性熔岩的母岩浆（碱性玄武质）产生于深度较大（～130km）、部分熔融程度较低（〈10％）的条件下,中-东部裂谷基性熔岩的母岩浆（拉斑玄武质）产生于深度稍浅（～100km）? 相似文献
6.
川西新元古代双峰式火山岩成因的微量元素和Sm-Nd同位素制约及其大地构造意义 总被引：44，自引：0，他引：44
系统的微量元素和Sm-Nd同位素分析表明,川西地区早震旦世苏雄组双峰式火山岩中的大多数玄武岩具有高的正εNd(T)值(+5～+6)、大离子亲石元素和LREE富集,与现代典型的洋岛玄武岩和大陆溢流玄武岩省中的碱性玄武岩有非常相似的地球化学和同位素组成特征。酸性火山岩的εNd(T)值较低(+1.1～+2.6),地球化学特征总体上与A2-型花岗岩相似,它们是受地壳混染的OIB型玄武质岩浆在地壳中部的一个“双扩散”岩浆房通过结晶分异形成的。苏雄组双峰式火山岩形成于典型的大陆裂谷环境,非常类似于现代与地幔柱活动有关的高火山活动型裂谷火山岩,扬子块体西缘 800Ma前的裂谷作用和火山活动应是约825Ma前的华南地幔柱活动引发的结果。 相似文献
7.
浙江淳安早白垩世脉岩地球化学特征及成岩动力学背景 总被引：1，自引：0，他引：1
在浙西淳安地区江绍断裂带内发育规模较大的基性脉岩,野外地质特征显示其产状与区域构造应力场的方向基本一致,总体呈北东—南西向,且与围岩之间的界限截然。对含斑基性脉岩进行了锆石LA-ICPMS U-Pb定年和详细的岩石地球化学特征研究,其锆石206Pb/238 U加权平均年龄为135Ma±2Ma(n=18,MSWD=3.2),代表其结晶年龄,为燕山期岩浆活动的产物,岩石地球化学特征显示形成于板内拉张的环境。整体特征显示含斑基性脉岩是由基性岩墙的岩浆混合了部分围岩物质形成的。该区的含斑基性脉岩与基性岩墙群的形成可能与太平洋板块向亚洲大陆的俯冲有关,是早白垩世岩石圈发生伸展减薄所诱发的地幔物质部分熔融的产物。 相似文献
8.
《四川地质学报》2022,(Z1):12-19
遮拉组OIB型玄武岩分布于特提斯喜马拉雅北带中段,围岩为泥质粉砂岩、粉砂质泥岩。地球化学特征表明,岩石具有较明显的低K_2O、中MgO和高TiO_2、P_2O_5、TFeO特征,(La/Yb)_N值为3.79～12.50,δEu=0.92～1.12,其稀土配分曲线呈略右倾的轻稀土富集模式,在原始地幔标准化蛛网图上,富集Rb、Ba、Th等大离子亲石元素及Nb、Ta、Zr、Hf、Ti等高场强元素,为大陆边缘裂谷背景的具有OIB型地球化学特征的碱性玄武岩。遮拉组OIB型玄武岩与含石榴石、尖晶石二辉橄榄岩部分熔融(Gt> Sp)有关,显示出岩石圈地幔物质的印记。玄武岩中捕获锆石年龄可能说明其源区存在古老的大陆碎块。岩石成因模式可以解释为正在孕育的地幔柱诱导的上涌软流圈物质与岩石圈地幔物质混合后在拉张背景下发生减压熔融的产物,这种地幔热柱或热点可能与Kerguelen热点的早期活动有联系,岩浆演化过程中发生了橄榄石和单斜辉石的分离结晶作用。 相似文献
9.
10.
《世界地质》2020,(3)
胶莱盆地北缘宋家沟金矿分布众多与矿化相互交切的中基性脉岩,针对这些中基性脉岩开展了详细的LA-ICP-MS锆石U-Pb年代学、岩石学和地球化学研究。结果显示,中基性脉岩可以划分为成矿前和成矿后两类脉岩,岩石类型分别为辉绿岩和闪长岩,两者ΣREE含量均相对较高,成矿前脉岩LREE/HREE比值介于12.76～15.52,成矿后脉岩LREE/HREE比值为18.72,均表现出LREE相对富集,HREE相对亏损的特征。成矿前、后脉岩显著富集大离子亲石元素(Rb、Ba)和高场强元素(U、Th)等,亏损Nb、Ti等高场强元素,表现出受地壳物质混染的板内玄武岩特征。成矿前脉岩锆石U-Pb年龄介于518～802 Ma之间,属捕获锆石年龄,成矿后脉岩锆石U-Pb年龄为121±5 Ma,结合前人获得的莱阳群地层最大沉积年龄(130±2 Ma),认为宋家沟金矿床的形成时间为121～130Ma。 相似文献
11.
Numerous early Cretaceous mafic and alkaline dykes, mostly trending in N-S direction, are emplaced in the Archaean gneissic
complex of the Shillong plateau, northeastern India. These dykes are spatially associated with the N-S trending deep-seated
Nongchram fault and well exposed around the Swangkre-Rongmil region. The petrological and geochemical characteristics of mafic
dykes from this area are presented. These mafic dykes show very sharp contact with the host rocks and do not show any signature
of assimilation with them. Petrographically these mafic dykes vary from fine-grained basalt (samples from the dyke margin)
to medium-grained dolerite (samples from the middle of the dyke) having very similar chemical compositions, which may be classified
as basaltic-andesite/andesite. The geochemical characteristics of these mafic dykes suggest that these are genetically related
to each other and probably derived from the same parental magma. Although, the high-field strength element (+rare-earth elements)
compositions disallow the possibility of any crustal involvement in the genesis of these rocks, but Nb/La, La/Ta, and Ba/Ta
ratios, and similarities of geochemical characteristics of present samples with the Elan Bank basalts and Rajmahal (Group
II) mafic dyke samples, suggest minor contamination by assimilation with a small amount of upper crustal material. Chemistry,
particularly REE, hints at an alkaline basaltic nature of melt. Trace element modelling suggests that the melt responsible
for these mafic dykes had undergone extreme differentiation (∼ 50%) before its emplacement. The basaltic-andesite nature of
these rocks may be attributed to this differentiation. Chemistry of these rocks also indicates ∼ 10–15% melting of the mantle
source. The mafic dyke samples of the present investigation show very close geochemical similarities with the mafic rocks
derived from the Kerguelen mantle plume. Perhaps the Swangkre-Rongmil mafic dykes are also derived from the Kerguelen mantle
plume. 相似文献
12.
青藏高原东南部出露有大量近东西向展布的(超)镁铁质岩墙,锆石U?Pb年龄聚集在145～130 Ma之间。矿物学及岩石学结果显示：哲古错地区的亚碱性超镁铁苦橄质岩石源于150～180 km深处, 5～6 GPa下石榴石二辉橄榄岩地幔高比率的部分熔融; 碱性超镁铁质岩石源于石榴石-尖晶石二辉橄榄岩转换带,是低比率部分熔融的产物; 镁铁质岩石的岩浆在演化过程中遭受了低压下结晶分离作用的改造,不能代表原始岩浆的成份。藏东南(超)镁铁质岩石是不同深度地幔物质不同比率部分熔融的产物,亚碱性超镁铁苦橄质岩墙的出现指示了晚侏罗-早白垩印度板块北缘存在的高比率部分熔融的岩浆活动事件,暗示了地幔柱的存在和影响。 相似文献
13.
华北克拉通中元古代裂解事件:以渣尔泰-白云鄂博-化德裂谷带岩浆与沉积作用研究为例 总被引：9，自引：7，他引：2
华北克拉通存在三个主要的中元古代裂谷带,从南到北分别为熊耳裂谷带、燕辽裂谷带以及渣尔泰-白云鄂博-化德裂谷带。其中熊耳群中火山岩的峰期年龄为1780~1750Ma,其上还有形成于被动大陆边缘的五佛山群、汝阳群以及官道口群。中北部的燕辽裂谷带包括长城系、蓟县系和青白口系,其中长城系团山子组和大红峪组火山岩的年龄分别为~1640Ma和1626~1622Ma,蓟县系高于庄组、雾迷山组和铁岭组凝灰岩的年龄分别为1560Ma、1485Ma和1437Ma,而下马岭组凝灰岩年龄为1366~1380Ma。北缘渣尔泰-白云鄂博-化德裂谷带中渣尔泰群书记沟组玄武岩年龄为1743Ma,阿古鲁沟组酸性火山岩年龄为~810Ma,白云鄂博群尖山组中基性火山岩年龄为1728Ma,化德群比鲁特组火山碎屑岩年龄为1515Ma。中元古代岩浆事件除了裂谷带中的火山作用外,还包括三期基性岩墙群(~1780Ma太行-吕梁岩墙群、~1730Ma密云岩墙群和~1620Ma泰山岩墙群)以及1.76Ga到1.65Ga非造山岩浆组合(斜长岩-环斑花岗岩体-A型花岗岩)。中元古代中期,华北克拉通北缘发育了基性岩席(墙)、A型花岗岩以及碳酸岩脉,双峰式岩浆作用说明华北北缘在中元古代中期经历了裂谷作用,与哥伦比亚超大陆的最终裂解有关,并且与白云鄂博巨型REE-Nb-Fe矿床的形成具有成因上的联系。华北克拉通北部两个裂谷带中的地层具有可以对比的层序以及时代,而中元古代中期辉绿岩墙、A型花岗岩以及碳酸岩脉可以与其它克拉通同时期的非造山岩浆作用对比,证明华北克拉通经历了哥伦比亚超大陆的最终裂解。古地磁数据已经证明在哥伦比亚超大陆时期Siberia、Laurentia、Baltica、Amazion以及华北克拉通是连接在一起的,而北缘中元古代中期大陆裂谷相关岩浆岩的发现也说明它是与另一个古大陆相连的。华北克拉通南缘熊耳火山岩的构造背景到底是大陆裂谷还是大陆边缘弧则关系着其是与另一个克拉通相连还是面向大海,这需要我们进一步深入研究。 相似文献
14.
The Damodar valley within the Chhotanagpur Gneissic terrain at the northern-most margin of the Singhbhum craton, eastern India, is perhaps the only geological domain in the entire Indian shield which hosts the early Cretaceous Rajmahal as well as the late Cretaceous Deccan igneous activities. A number of Cretaceous mafic dykes intrude the Gondwana sedimentary formations and are focus of the present study. One set of these dykes strike NNE to ENE, are very fresh and mainly exposed within the Jharia, Bokaro and Karanpura basins; whereas the other set of dykes (including the well-known Salma mega dyke) trend NW to NNW, intrude mainly the Raniganj basin and show meagre hydrothermal alteration. Majority of the samples from both these dyke groups display ophitic or sub-ophitic textures and are essentially composed of augite/titan augite and plagioclase. On the basis of petrographic and geochemical characteristics the NNE to ENE dykes are identified as high-Ti dolerite (HTD) dykes and the NW to NNW dykes are referred to as low-Ti dolerite (LTD) dykes. Apart from the first-order distinction on their titanium contents, both these groups also show conspicuous geochemical differences. The HTD dykes contain relatively high values of iron, and high-field strength elements than those from the LTD dykes with an overlapping MgO contents.Although available field, paleomagnetic and limited geochronological data for most of the studied dykes suggests their emplacement during early Cretaceous period (110–115 Ma), the Salma dyke, dated to be of Deccan-age at ∼65 Ma, is an exception. Geochemically all the studied samples show an undoubted plume-derived character but their unequivocal affinity to either the early Cretaceous Kerguelen (Rajmahal) or the late-Cretaceous Reunion (Deccan) plume is not straightforward since they share bulk-rock characteristics of rocks derived from both these plumes. Even though, the spatial and temporal association of the mafic dykes of present study with the Rajmahal Traps are suggestive of their linkage to the Kerguelen plume activity, robust geochronological and paleomagnetic constraints are clearly required to understand the relative contributions of the two Cretaceous mantle plumes in the genesis of the mafic igneous activity in this interesting domain. 相似文献
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16.
In the Beishan rift in the eastern Tianshan orogen, Xinjiang Province, a N-S-trending dyke swarm is present in the Pobei area. The swarm cuts through the 270–290 Ma mafic-ultramafic intrusions associated with Ni-Cu sulphide mineralization. These mafic-ultramafic intrusions are typically found along E-W major faults in the Tianshan orogenic belts. We report SHRIMP U-Pb dating of zircons from a dyke of alkaline composition, which yielded a mean age of 252±9 Ma. Alkaline dykes of the same age are found in the Altay region of Siberia. This age is younger than the 270–290 Ma intraplate magmatic events that produced the mafic-ultramafic intrusions in the region, but in general agreement with the 250–260 Ma Permian plume event that gave rise to the Siberian traps and the Emeishan flood basalts in SW China. We suggest that there is a link between the Emeishan event and the dyke swarm in the Beishan rift and that the intraplate magmatism at 270–290 Ma reflects an early stage of mantle plume activity. The N-S trending dyke swarm in the Beishan rift may represent a later stage in the evolution of mantle plume activity in the NW and SW of China. We also speculate that in Beishan rift and possibly elsewhere in the Tianshan region, the dykes fed basaltic volcanism, whose products have since been eroded due to the strong uplift of the Tianshan orogen as a result of the India-Eurasia collision in the Cenozoic. 相似文献
17.
《地学前缘(英文版)》2020,11(6):2127-2139
The Dharwar Craton in Peninsular India was intruded by a series of mafic dykes during the Paleoproterozoic and these mafic magmatic events have important implications on continental rifting and LIPs. Here we report ten precise Pb–Pb TE-TIMS age determinations on baddeleyite grains separated from seven mafic dykes and three sills, intruding into Archean basement rocks and Proterozoic sedimentary formations of the Eastern Dharwar Craton respectively. The crystallization age of the baddeleyite shows 2366.3 ± 1.1 Ma, and 2369.2 ± 0.8 Ma for the NE–SW trending dykes, 2368.1 ± 0.6 Ma, 2366.4 ± 0.8 Ma, 2207.2 ± 0.7 Ma and 1887.3 ± 1.0 Ma for the ENE–WNW to E–W striking dykes, 1880.6 ± 1.0 Ma, 1864.3 ± 0.6 Ma and 1863.6 ± 0.9 Ma for Cuddapah sills, and 1861.8 ± 1.4 Ma for the N–S trending dyke. Our results in conjunction with those from previous studies identify eight distinct stages of widespread Paleoproterozoic magmatism in the Dharwar craton. The mantle plume centres of the four radiating dyke swarms with ages of ~2367 Ma, ~2210 Ma, ~2082 Ma, and ~1886 Ma were traced to establish their proximity to the EDC kimberlite province. Though the ~2367 Ma and ~1886 Ma plume centres are inferred to be located to the west and east of the present day Dharwar craton respectively away from the kimberlite province, location of plume heads of the other two swarms with ages of ~2207 Ma and ~2082 Ma are in close proximity. In spite of the ubiquitous occurrence of dyke intrusions of all the seven generations in the kimberlite province, only few of these kimberlites are diamondiferous. Kimberlite occurrences elsewhere in the vicinity of older Large Igneous Provinces (LIPs) like the Mackenzie, Karoo, Parana-Etendeka and Yakutsk-Vilui are also non-diamondiferous. This has been attributed to the destruction of the lithospheric mantle keel (that hosts the diamonds) by the respective mantle plumes. The diamondiferous nature of the EDC kimberlites therefore suggests that plume activity does not always result in the destruction of the mantle keel. 相似文献
18.
Neoproterozoic Mafic Dykes and Basalts in the Southern Margin of Tarim, Northwest China: Age, Geochemistry and Geodynamic Implications 总被引：4，自引：0，他引：4
<正>Neoproterozoic rifting-related mafic igneous rocks are widely distributed both in the northern and southern margins of the Tarim Block,NW China.Here we report the geochronology and systematic whole-rock geochemistry of the Neoproterozoic mafic dykes and basalts along the southern margin of Tarim.Our zircon U-Pb age,in combination with stratigraphic constraint on their emplacement ages,indicates that the mafic dykes were crystallized at ca.802 Ma,and the basalt, possibly coeval with the ca.740 Ma volcanic rocks in Quruqtagh in the northern margin of Tarim. Elemental and Nd isotope geochemistry of the mafic dykes and basalts suggest that their primitive magma was derived from asthenospheric mantle(OIB-like) and lithospheric mantle respectively,with variable assimilation of crustal materials.Integrating the data supplied in the present study and that reported previously in the northern margin of Tarim,we recognize two types of mantle sources of the Neoproterozoic mafic igneous rocks in Tarim,namely the matasomatized subcontinental lithospheric mantle(SCLM) in the northern margin and the long-term enriched lithospheric mantle and asthenospheric mantle in the southern margin.A comprehensive synthesis of the Neoproterozoic igneous rocks throughout the Tarim Block led to the recognition of two major episodes of Neoproterozoic igneous activities at ca.820-800 Ma and ca.780-740 Ma,respectively.These two episodes of igneous activities were concurrent with those in many other Rodinian continents and were most likely related to mantle plume activities during the break-up of the Rodinia. 相似文献
19.
Giant radiating mafic dyke swarm of the Emeishan Large Igneous Province: Identifying the mantle plume centre 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Hongbo Li Zhaochong Zhang Richard Ernst Linsu Lü M. Santosh Dongyang Zhang Zhiguo Cheng 《地学学报》2015,27(4):247-257
In many continental large igneous provinces, giant radiating dyke swarms are typically interpreted to result from the arrival of a mantle plume at the base of the lithosphere. Mafic dyke swarms in the Emeishan large igneous province (ELIP) have not received much attention prior to this study. We show that the geochemical characteristics and geochronological data of the mafic dykes are broadly similar to those of the spatially associated lavas, suggesting they were derived from a common parental magma. Based on the regional geological data and our field observations, we mapped the spatial distribution patterns of mafic dyke swarms in the ELIP, and recognized six dyke sub‐swarms, forming an overall radiating dyke swarm and converging in the Yongren area, Yunnan province. This location coincides with the maximum pre‐eruptive domal uplift, and is close to the locations of high‐temperature picrites. Our study suggests that the Yongren area may represent the mantle plume centre during the peak of Emeishan magmatism. 相似文献