Geochemistry and tectonic implications of Proterozoic amphibolites in the northeastern part of the Yeongnam massif, South Korea   总被引：1，自引：0，他引：1  

Yoji Arakawa  Kye-Hun Park  Nam-Hoon Kim  Yong-Sun Song  Hiroshi Amakawa 《Island Arc》2003,12(2):180-189

Abstract   Amphibolites in the Haenggongni area (Haenggongni amphibolite) and the Okbang area (Okbang amphibolite) in northeastern Yeongnam massif, South Korea occur as a sill-like body or inclusions within the metasedimentary sequences of the Proterozoic Wonnam Group. Major and trace element characteristics demonstrate that both amphibolites have tholeiitic chemical affinity. They are characterized by nearly flat rare earth element (REE) patterns, and low contents of immobile incompatible elements and have low values of Zr/Y, Ti/Y, La/Nb and Ta/Yb ratios, indicating enriched (E)-type mid-oceanic ridge basalt (MORB) affinities for their protoliths. This suggests that amphibolite protoliths formed in an extensional rift setting leading up to ocean opening. In combination with the previous studies in Yeongnam massif, three protolith types of amphibolites are assumed (E-type MORB, within-plate basalt and volcanic arc basalt). They could have been originated in different tectonic settings and/or different episodes. These characteristics are clearly different from the amphibolites in the Gyeonggi massif and Okcheon belt, in which most of the amphibolites show a within-plate basalt affinity that developed in continental rift zone.  相似文献   

黔东—湘西早古生代岩石圈热状态与高产热率HHPRM型地幔源区   总被引：1，自引：0，他引：1  

方维萱  胡瑞忠  苏文超  漆亮  蒋国豪 《大地构造与成矿学》2002,26(4):337-344

岩石圈热结构和热状态的研究对于大陆裂解、变质作用及活化构造形成机制等大陆动力学问题的研究十分重要。通过地球化学、构造地质学和综合分析,以贵州省镇远地区金伯利岩-钾镁煌斑岩和黔东—湘西一带的晚元古代地层为例,研究了扬子地块东南缘早古生代岩石圈热结构与热状态。提出高放射性元素产热率的HHPRM型地幔源区,进一步讨论HHPRM型地幔源区形成与演化的大陆动力学机制。认为古富集地幔(HHPRM型地幔源区)是镇远一带的早古生代钾镁煌斑岩-金伯利岩的岩浆源区,镇远地区金伯利岩-钾镁煌斑岩岩浆源区深度(H)在208～244km,形成温度在1547～1403℃间,该温度和深度范围属软流层,具有形成金刚石矿床的地质条件。建议在贵州—湖南—广西三省交界区的金伯利岩和钾镁煌斑岩岩群中应进一步开展金刚石矿床研究与勘查工作。  相似文献   

西金乌兰构造混杂带中基底变质岩的特征和意义     

王永文  李善平  王发明 《西北地质》2004,37(1):40-44

在可可西里的西金乌兰湖一带首次发现了基底变质岩。岩石组合以石英质变质岩石组成。原岩为沉积建造。出露仅限于西金乌兰构造混杂带内。根据区域对比，认为是羌塘陆块的结晶基底。说明西金乌兰构造混杂带是羌塘陆块上裂解形成的。  相似文献   

阿拉善地块南缘镁铁-超镁铁岩形成时代及地球化学特征   总被引：7，自引：0，他引：7  

李文渊  汤中立  郭周平  王伟 《岩石矿物学杂志》2004,23(2):117-126

阿拉善地块南缘是镁铁超镁铁岩体的重要分布区 ,自北而南可分为北大山岩带、龙首山岩带和北海子岩带。北大山岩带以野芨里含长辉石橄榄岩侵入体为代表 ,Sm_Nd岩石矿物等时线年龄为 773.1± 10 .8Ma,εNd(t)=+0 .8～ +10 .8,ΣREE为 7.5 9× 10 -6～ 2 0 .34× 10 -6;龙首山岩带以金川二辉橄榄岩体和藏布台单辉橄榄岩为典型代表 ,Sm_Nd岩石矿物等时线年龄分别为 15 0 8± 31Ma和 15 11± 16 8Ma ,基本为同期幔源产物 ,金川岩体平均ΣREE为 3.33× 10 -6～ 115 .5 2× 10 -6,εNd(t) =- 1.9～ - 4 .3,藏布台εNd(t) =+2 .6～ +2 .9,差异显著 ;北海子岩带岩体分布有限 ,其中辉长岩体Sm_Nd岩石矿物等时线年龄为 14 4 0± 2 2 0Ma ,εNd(t) >0 ,ΣREE为 179.6 4× 10 -6～ 2 0 7.76× 10 -6。龙首山岩带和北海子岩带可能同为中元古代早期超地幔柱作用下地幔派生岩浆的产物 ,εNd(t)值的差异反映了各自岩体成岩过程的不同 ;野芨里岩体形成于新元古代 ,是亏损地幔的产物 ,与金川等岩体的形成环境和物质来源有显著不同。  相似文献   

粤北下庄花岗岩地球化学特征与成因研究   总被引：10，自引：0，他引：10  

吴烈勤  黄国龙  沈渭洲  凌洪飞  叶海敏  刘汝洲  邹志文 《铀矿地质》2005,21(2):65-71

印支期下庄花岗岩是粤北贵东复式花岗岩体的重要组成部分, 其岩石的主要元素显示出富硅、富碱、过铝质等特征; 微量元素表现为富集Rb、Th、U、Ce、Sm、Y, 亏损Ba、Sr、P、Ti;LREE轻微富集 (LREE/HREE=7 .54~11 18, (La/Yb)N=7 .36~16.03), Eu亏损明显 (δEu=0 .24~0 .33); 构造环境判别显示下庄花岗岩属于后碰撞花岗岩范畴。这些特征表明, 下庄岩体属于典型的壳源型花岗岩, 是在地壳伸展减薄的构造背景下, 通过以泥质岩和砂质岩组成的古元古代变质沉积岩部分熔融而形成。  相似文献   

Tectonometamorphic evolution of the Chuncheon amphibolite, central Gyeonggi massif, South Korea   总被引：9，自引：0，他引：9  

SEUNG RYEOL LEE  MOONSUP CHO 《Journal of Metamorphic Geology》1995,13(2):315-328

Abstract The Chuncheon amphibolite, part of the Gubongsan Group which overlies the Yongduri gneiss complex, is interlayered with calc-silicate rock, marble, quartzite, biotite schist and quartzofeldspathic gneiss in the central Gyeonggi massif, South Korea. Metamorphic pressures and temperatures estimated from the amphibolite are 5.5–10.6 kbar and 615–714°C. These P—T conditions are close to those defined by the reaction curve between kyanite and sillimanite, and suggest medium-pressure-type metamorphism of the Chuncheon amphibolite. For two metapelites intercalated with the amphibolite, temperatures are estimated to be 607–699° C, consistent with those obtained from the amphibolite. On the other hand, pressures estimated from these metapelites are significantly different, 4–6 kbar and 9–13 kbar, when rim and core compositions of garnet are, respectively, used. These P—T estimates obtained from the amphibolite and metapelite suggest a nearly isothermal decompression of 3–7 kbar during denudation. Rapid decompression is likely on the basis of the results of mineral chemistry, phase equilibria and geothermobarometer. Moreover, in conjunction with the occurrence of kyanite in the adjacent Gyeonggi gneiss complex, P—T estimates of the Chuncheon amphibolite and metapelite suggest a clockwise P—T—t path. This evolutionary path may be related to the amalgamation of continents during the late Proterozoic event which corresponds to the Jinningian orogeny in the Qinling belt of China.  相似文献   

博尔塔拉河断裂及其大地构造意义     

李向东  秦跃群 《新疆地质》1989,(1)

博尔塔拉河断裂自前加里东期形成以来,经历了长期持续的构造活动,使断裂规模、深度渐大,形态愈加复杂.大量的地壳硅铝层的岩浆活动和近代频繁发生的浅源弱震,证实断裂下切深度基本达地壳硅铝层下部,可作为阿拉套华力西褶皱带和赛里木地块的界线,断裂两侧构造层同属天山地槽褶皱带.  相似文献   

华南裂陷系的建造特征和构造演化   总被引：8，自引：1，他引：8  

杨森楠 《地球科学》1989,14(1):29-36

  相似文献   

Delineation of a large ultramafic massif embedded within a major SW Pacific suture using gravity methods     

Helen A. Williams  John Cassidy  Corinne A. Locke  K. Bernhard Sprli 《Tectonophysics》2006,424(1-2):119-133

Gravity studies have delineated the largest ultramafic massif in New Zealand, embedded within a buried major SW Pacific crustal suture zone. This suture records terrane collision onto the Gondwana margin during the Mesozoic and separates a forearc terrane from an outboard accretionary prism terrane. It can be traced throughout the length of New Zealand as the Junction Magnetic Anomaly and contains the Permian Dun Mountain Ophiolite Belt, which in the South Island of New Zealand is characterized by a string of isolated ultramafic massifs in a sheared matrix of serpentinite and sediment. Our analysis reveals a steep gravity gradient at the suture boundary which is attributed to a newly recognised density contrast (0.1 Mg m^− 3) between terranes of the forearc and the accretionary prism. The massif itself is marked by the occurrence of a strong, elongate residual gravity anomaly (+ 120 g.u.) extending 50 km along the suture and coincident with the Junction Magnetic Anomaly. It is modelled, at its southern end, as a dense, 15 km wide source body, extending to at least 6 km in depth. In conjunction with detailed aeromagnetic data, this modeling indicates the presence of a spindle-shaped ultramafic massif, analogous to, but larger than similar bodies found within the Dun Mountain Ophiolite Belt elsewhere. This fabric of sheared serpentinites enclosing ultramafic massifs therefore extends at least the length of New Zealand and probably beyond. In part it may result from accretion of asperities in the subducting plate, but it is also due to disruption of larger ultramafic bodies during subsequent strike-slip motion, which caused the remarkable linearity of the Dun Mountain Belt. Given the common occurrence of the plate tectonic processes involved, it is likely that such structures can be found in other regions around the world using similar geophysical potential field methods.  相似文献   

若尔盖地块三叠系泥质岩微量元素地球化学特征与构造背景     

孟伟  李巨初  刘树根 《四川地质学报》2007,27(1):2-6

研究了若尔盖地区三叠系泥质岩微量元素地球化学特征。三叠系各地层样品中轻稀土显著富集,重稀土变化平缓,稀土总量为173.41×10-6~238.46×10-6,其变化不大。稀土含量与中国东部泥质岩相比差别不大。微量元素地球化学特征表明本区三叠系物源为大陆岛弧。  相似文献