共查询到20条相似文献，搜索用时 140 毫秒
1.
柴达木地块古地磁研究及其演化 总被引：1，自引：0，他引：1
根据柴达木地块获得的6个古地磁数据,结合已知的古地磁数据阐述了柴达木地块及与相邻板块间的演化模式.结果表明柴达木地块从震旦纪到石炭纪一直处于赤道附近和低纬度地区.石炭纪时,柴达木、杨子及走廊过渡带三地块均处在赤道附近,三者可能是连在一起的.而华北板块与上述三地块至少有10°左右的纬向差,因此,华北与柴达木、杨子和走廊过渡带当时还没有连在一起. 相似文献
2.
用逐步热退磁方法对黑龙江省兴华渡口剖面104块变质岩的定向标本进行了系统处理,获得了该剖面的各项古地磁参数:中元古代下兴华组的古地磁极位置λ_p=203.1°E,古纬度.由次生剩磁推断得中寒武纪古地磁极位置λ_p=174.4°E,古纬度.古地磁结果表明,额尔古纳地块在中元古下兴华组时应与阿尔丹地块相连,中寒武纪时才并入西伯利亚板块.从中元古到中寒武额尔古纳地块应位于南半球的中、低纬度地带. 为了检验标本剩磁的稳定性除对它进行逐步热退磁而外,还对它进行了烘烤检验与褶皱检验. 相似文献
3.
阿拉善地块的大地构造属性是近年来地质界激烈争论的科学问题:是华北克拉通的一部分,还是在前寒武纪尚未与华北克拉通拼合?研究阿拉善地块的基底并与华北克拉通主体进行对比,对探讨这一问题具有重要启示。阿拉善地块的基底仅在其东部和西南缘零星出露,且前人的研究主要集中在地块东部。在阿拉善地块西部的合黎山地区,有正长岩侵入龙首山群,并被震旦系不整合覆盖。该正长岩强烈富钾(K_2O=13.77%),轻、重稀土明显分异((La/Yb)_N=46.62),显示Nb-Ta负异常和Pb-Zr-Hf正异常,并具有高Sr低Nd的同位素特征(ε_(Nd)(t)=-5.05),表明该岩体源于玄武质下地壳的部分熔融。LA-ICP-MS锆石U-Pb定年表明,该正长岩形成于(1872±12) Ma,即古元古代,并记录了～2.7 Ga的地壳生长以及～2.5 Ga和～1.95 Ga的岩浆活动。合黎山古元古代正长岩的发现补充了阿拉善地块前寒武纪基底的组成,进一步完善了阿拉善地块新太古代—古元古代基底和构造热事件的时代格架,且与华北克拉通主体十分相似,指示二者具有明显的亲缘性。 相似文献
4.
古亚洲洋和古特提斯洋的闭合时代——论二叠纪末生物灭绝事件的构造起因 总被引：7，自引：1，他引：6
通过对比分析华南地块和基墨里大陆（包括保山、缅泰和羌塘地块）间、华北和西伯利亚地块间的古纬度和纬度运移量,分别确定了古特提斯洋和古亚洲洋的闭合时代。结果表明：（1）基墨里大陆东部的保山地块与华南地块于晚二叠世碰撞,然后继续和华南地块、缅泰地块、羌塘地块一起向北漂移,直到晚三叠世,即在云南三江地区,古特提斯洋的闭合时代为晚二叠世晚期; （2）早二叠世西伯利亚地块开始快速向南漂移,并于二叠纪末期（～250 Ma）和华北地块发生碰撞,即位于两地块间古亚洲洋最终闭合时代为二叠纪末;（3）峨眉山和西伯利亚两个大火成岩省的形成时代和大洋的闭合时代吻合,而大火成岩省在时间上又与全球生物灭绝事件吻合,进而推断二叠纪末的生物灭绝事件可能与古亚洲洋和古特提斯洋的闭合密切相关。 相似文献
5.
晚古生代－三叠纪，滇黔桂三省区和越南北部有南盘江海长期发育。地质构造上，北面为扬子地块，东南有云开地块和大明山微陆块，西南有越北地块。南盘江海内部有北部的田林海盆，中部的八布洋盆和南部的钦防海盆。中间有许多大小不一的海下台地，最大的是大明山台地，其次是靖西台地和西畴台地。早泥盆世晚期南盘江海的张开，可能是冈瓦纳板块反时针旋转、扬子地块北移，使其间滇桂－越北地块裂解的结果。进一步的海底扩张导致早石炭世时八布海盆出现洋壳，南盘江海成为南北超过20个纬度的小洋盆。古地理再造表明，八布海盆的扩张脊可能连接西面哀牢山海的洋脊。晚二叠世云开地块北移，与大明山微陆块碰撞。早三叠世印支地块北移，和越北地块会聚。晚二叠世－中三叠世南盘江海南缘出现活动陆缘。晚三叠世印支－越北地块与扬子地块会聚，南盘江海闭合。南盘江海和哀牢山海及昌宁－孟连海的发生、发展和消亡基本同步，可能属古特提斯同一洋脊系统控制。 相似文献
6.
甘肃玉门地区二叠系-三叠系古地磁研究 总被引：1，自引：0，他引：1
玉门大山口白杨河一带古地磁研究结果:下二叠统的特征磁化方向为Ds=108.1°,Is=-46.1°;极点位置为λ=30.5°N,ψ=18.6°;古纬度为27.6°N.上二叠统的特征磁化方向为Ds=139.4°,Is=-47.4°;极点位置为λ=54.7N,ψ=359.9°;古纬度为28.2°N;下三叠统的特征磁化方向为Ds=150.8°,Is=-48.1°;极点位置为λ=63.7°N,ψ=351.1°;古纬度为29.1°N.说明二叠纪玉门地区所在的阿拉善地块已是华北地块的一部分,晚二叠世-早三叠世华北地块大体处于吐哈地块和华南地块之间,与俄罗斯地块的古纬度相近;华北、吐鲁番-哈密和塔里木地块都大体位于劳亚大陆的东南部. 相似文献
7.
羌塘地块中生代时期的漂移演化及其成钾条件 总被引：1，自引：0，他引：1
通过研究地块的古纬度,可以为我们认识该地块在地质历史时期的古地理位置和南北向漂移演化提供定量约束。本文通过收集、整理、评判中生代时期羌塘地块已发表的古地磁数据,建立了该地块在中生代时期的漂移演化历史。羌塘地块在中—晚三叠世期间,可能发生大规模快速北向漂移,并与羌塘北部的构造单元体发生碰撞;中侏罗世时期位于北半球21.4°N,晚侏罗世期间已北向到达31.8°N。中晚侏罗纪期间,羌塘地块古纬度值逐步升高,发生约1154±223km(△λ=10.4°±2.1°)的北向漂移。白垩世期间羌塘地块相对稳定,在古纬度30°N左右。综合上述羌塘地块的漂移演化历史,结合其它地质证据,如古气候、构造和从古地理位置等,中晚侏罗世夏里组时期羌塘地块具备较好的成钾条件。 相似文献
8.
通过对柴达木地块天峻县组合玛地区晚二叠世13个采点的系统古地磁测定,揭示了一组高温特征剩磁分量.实验结果表明,采样剖面获得的晚二叠世古地磁结果具有正、反极性,其特征剩磁方向为:Dg=333.7°,Ig=37.3°,Kg=35.4,N=9,α95 =8.8;Ds=333.9°,Is=41.7°,Ks=69.9,α95 =6.2°,相对应的古地磁极位置为:64.0°N,342.4°E,A95=5.9°,古纬度为24.0°N.这一高温分量通过了倒转检验,我们认为这一高温特征剩磁分量很可能代表了研究区晚二叠世时期的原生特征剩磁.通过对比塔里木地块晚石炭-晚二叠世古地磁结果,发现两块体在晚石炭世存在明显的古纬度差(16.6±9.3°),而在晚二叠世其古纬度差(3.5±5.4°)在古地磁误差范围内并没有明显差别,从构造意义上说,说明柴达木地块在晚二叠世已是塔里木地块的一部分,结合地质资料,认为柴达木地块在晚二叠世时古地理位置处于塔里木地块的南缘或西南缘,这表明柴达木/塔里木地块间的古阿尔金断裂的形成时代不可能早于晚石炭世时,很可能形成于晚二叠世以后. 相似文献
9.
古特提斯洋的闭合时代的古地磁分析:松潘复理石杂岩形成的构造背景 总被引：3，自引：0，他引：3
对华南地块、塔里木地块和基墨里大陆(包括保山、缅泰和羌塘地块)进行了古纬度和纬度运移量的对比分析,以确定古特提斯洋盆的闭合时代。结果表明：①保山与华南地块于晚二叠世碰撞,然后继续和华南地块、缅泰地块一起向北漂移,直到晚三叠世,并导致华南地块与华北地块碰撞和秦岭—大别造山带的形成;②羌塘地块与塔里木地块碰撞发生在晚三叠世;古特提斯洋沿着保山地块东缘和羌塘地块北缘的闭合是不同时的,东早西晚;③华南地块向北漂移,可能引起了华南地块西部和东昆仑—柴达木地块南部的古特提斯洋北岸的凹入,这为松潘—甘孜海底扇的发育提供了空间;古特提斯洋闭合引起的俯冲造成了华南地块西部大陆边缘的裂离,也共同为海底扇的发育提供了空间。包括塔里木地块、华南地块、东昆仑—柴达木地块和羌塘地块在内的几个地块的合围,导致了松潘—甘孜地块三角形的构造形状。支持以前的假设：松潘—甘孜三叠纪复理石杂岩的物源来自华北地块南缘或秦岭—大别造山带。 相似文献
10.
阿拉善地块前中生代构造归属的新认识 总被引：4，自引：0，他引：4
阿拉善地块的构造归属长期以来存在争议。我们对阿拉善地块东南部牛首山地区中—晚泥盆世砂岩的物源开展碎屑锆石U-Pb年代学与Hf同位素研究。碎屑锆石U-Pb年龄谱主要分布在5个区间:0.4—0.7 Ga,1.0—1.3 Ga,1.5—1.8 Ga,2.4—2.8 Ga和3.0 Ga,并获得一颗年龄为(4022±17)Ma的冥古宙锆石。2.4—2.7 Ga、3.0 Ga碎屑锆石和它们对应的εHf(t)值明显不同于华北板块同时代碎屑锆石,暗示着阿拉善地块与华北板块中—晚泥盆世并未相连。同时,我们还对地块东部的早石炭世、晚二叠世和早中三叠世地层开展了详细的古地磁研究,获得了相应的视极移曲线。我们结合碎屑锆石年代学和古地磁学研究,提出阿拉善地块前中生代与柴达木—塔里木地块具有亲缘性,而很可能与华北地块分离。印支运动使阿拉善地块相对于华北发生了32度的逆时针旋转,正是这一旋转运动使河西走廊—阿拉善地块最终与华北地块拼合形成了统一地块。 相似文献
11.
《International Geology Review》2012,54(6):494-507
The Jurassic Mayari-Baracoa ophiolite belt and associated Cretaceous volcanic rocks form the Zaza zone of eastern Cuba. This zone has been traditionally considered allochthonous and overrides a passive continental margin, the Cuban foreland. The ophiolites consist of mantle tectonites and cumulates, overlain by a volcanicarc sequence including porphyritic basalts and andesitic lavas. These are, in turn, overlain by a sequence of tuffs and epiclastic sedimentary rocks. There are two ophiolitic massifs in the belt, the Mayari-Cristal Massif (MCM) and the Moa-Baracoa Massif (MBM). The MCM consists of harzburgites and dunites with abundant high-Cr podiform chromitites and dikes of gabbro and pyroxenite. The MBM, on the other hand, is composed of harzburgites with abundant high-Al podiform chromitites, cut by troctolite dikes. The two ophiolitic massifs have different REE and PGE patterns and contents. The mantle sequence in the MCM is more depleted than that in the MBM. We suggest that the MCM formed beneath a volcanic island arc and the MBM beneath a nascent spreading center in a back-arc basin. The two massifs form a paired ophiolite belt. 相似文献
12.
WANG Qian WANG Shi-yu HU Yan-fei College of GeoExploration Science Technology Jilin University Changchun China 《吉林大学学报(地球科学版)》2006,(Z2)
利用MT资料研究位于佳木斯地块和兴凯地块之间过渡地带的岩石圈结构特征。由资料处理所得到的2D反演结果分析出过渡带(属于完达山地体)的地电特征:上部地壳的地电参数在横向上变化较大,中下部地壳所存在的低阻层带可延伸至兴凯地块岩石圈地幔之中,是否在更深位置延伸至佳木斯地块岩石圈地幔还不能确定。两古老地块的高阻特征存在一定的差异,即佳木斯地块的阻值明显高于兴凯地块。即完达山地体的南部作为两古老地块之间的过渡带,可能发生过古大洋洋中脊软流圈物质的垂向对流(上涌),并发生岩石圈板片向两古地块的俯冲过程。 相似文献
13.
14.
Michael Biste 《Journal of Geochemical Exploration》1981,15(1-3)
In contrast to the granitoids of the ultrametamorphic basement of northern Sardinia, Hercynian intrusive granites exist in southern Sardinia in low-grade metamorphic surroundings. In this area, endogenous cassiterite-bearing vein deposits and molybdenumtungsten mineralizations occur adjacent to the granite massifs of the Quirra (3), Arburese (4) and Monte Linas (5). In comparison, the intrusives of the Sarrabus (1) and San Vito (2) seem to be barren.Petrochemically these granitoids represent a spatial and temporal suite of calc-alkaline magmas with biotite-muscovite granite as a latest product of the magmatic evolution. The formation of the massifs was governed mainly by in situ differentiation. Only locally is there evidence of emanative differentiation processes which also caused post-magmatic metasomatic alteration of the granite and the formation of the hypothermal mineralization.According to their trace element geochemistry there exist normal and anomalous leucogranites. Thus, the Quirra (3), Monte Linas (5) and Arburese (4) massifs exhibit the highest grade of geochemical specialization. However, compared with highly tin-bearing granites in other regions, these massifs show only a slight specialization. Structural arguments suggest that the Arburese Massif (4) could have lost its higher specialized cupola and some possible deposits by erosion. In addition, only the drainage system of the Monte Linas Massif (5) exhibits anomalous tin concentrations in the alluvial sediments of recent channels. 相似文献
15.
Jacobo Abati Pedro Castieiras Ricardo Arenas Javier Fernndez‐Surez Juan Gmez Barreiro Joseph L. Wooden 《地学学报》2007,19(6):432-439
Abstract Dating of zircon cores and rims from granulites developed in a shear zone provides insights into the complex relationship between magmatism and metamorphism in the deep roots of arc environments. The granulites belong to the uppermost allochthonous terrane of the NW Iberian Massif, which forms part of a Cambro‐Ordovician magmatic arc developed in the peri‐Gondwanan realm. The obtained zircon ages confirm that voluminous calc‐alkaline magmatism peaked around 500 Ma and was shortly followed by granulite facies metamorphism accompanied by deformation at c. 480 Ma, giving a time framework for crustal heating, regional metamorphism, deformation and partial melting, the main processes that control the tectonothermal evolution of arc systems. Traces of this arc can be discontinuously followed in different massifs throughout the European Variscan Belt, and we propose that the uppermost allochthonous units of the NW Iberian Massif, together with the related terranes in Europe, constitute an independent and coherent terrane that drifted away from northern Gondwana prior to the Variscan collisional orogenesis. 相似文献
16.
块体拼贴是东北大地构造格架的基本特征,文中拟从这一构造背景出发,在区域地质研究基础上,选择目前研究相对薄弱的松嫩地块进行讨论。通过地层建造、古生物地理分区、构造岩浆组合及年代学的资料,揭示松嫩地块与东北其他地质体拼贴的历史。松嫩地块西侧通过嫩江中古生代造山带与兴安褶皱带相接;南侧通过吉中晚古生代造山带和华北地台北缘的西拉木伦早古生代褶皱带相接;东侧通过张广才岭中生代造山带与佳木斯地块拼贴;北侧是蒙古-鄂霍茨克中生代造山带。此外,结合前人关于全球构造格局变迁的研究,讨论了东北地块的来源,并认为松嫩地块东界的张广才岭造山带是古亚洲洋构造域向太平洋构造域转折的标志。 相似文献
17.
Ali Elmas İsak Yılmaz Erdinç Yiğitbaş Thomas Ullrich 《International Journal of Earth Sciences》2011,100(6):1251-1263
In the eastern part of the Strandja Massif constituting the east end of the Rhodope Massif, the amphibolite facies basement
rocks intruded by Permian metagranites are juxtaposed against the greenschist facies cover metasediments of Triassic-Middle
Jurassic protolith age. The distinct metamorphic break between the basement and cover rocks requires a missing metamorphic
section. The boundary between the two groups of rocks is a ductile to brittle extensional shear zone with kinematic indicators
exhibiting a top to the E/NE shear sense. Footwall rocks are cut by weakly metamorphosed and foliated granite bodies which
are clearly distinguished from the Permian metagranites by their degree of deformation, cross-cutting relations and syn-tectonic/kinematic
character. Also, hangingwall rocks were intruded by unmetamorphosed and weakly foliated leucogranites. 40Ar/39Ar data indicate that the ductile deformation from 156.5 to 143.2 Ma (Middle Oxfordian-Earliest Berriasian) developed during
the syn-tectonic plutonism in the footwall. Deformation, and gradual/slower cooling-exhumation survived until to 123 Ma (Barremian).
The mylonitic and brittle deformation in the detachment zone developed during Oxfordian-Earliest Berriasian time (155.7–142.6 Ma)
and Early Valanginian-Aptian time (136–118.7 Ma), respectively. Our new field mapping and first 40Ar/39Ar ages demonstrate the existence of an extensional core complex of Late Jurassic-Early Cretaceous age not previously described
in the Rhodope/Strandja massifs. 相似文献
18.
Complex mineralogical, geochemical, and geochronological studies of the gabbroids from the Dzhigdinskii Massif located in the western part of the Dzhugdzhur–Stanovoy Superterrane are performed. It is established that the age of the rocks from the Dzhigdinskii Massif is Middle Triassic (244 ± 5 Ma), rather than Early Archean, as was previously assumed. The age of the Dzhigdinskii Massif is close to the age of the formation of the other Triassic gabbroid massifs, such as the Amnunaktinskii (~240 Ma), Lukindinskii (~250 Ma), and Luchinskii (~248 Ma) in the southeastern environ of the North Asian Craton. One of the stages in the formation of the Selenga–Vitim volcanoplutonic belt falls in this period as well. This indicates that the Selenga–Vitim volcanoplutonic belt, along with the granitoids and volcanic rocks, is composed of ultrabasic–basic and basic massifs and that this belt is superposed on the structures of the Selenga–Stanovoy Superterrane, as well as on the western part of the Dzhugdzhur–Stanovoy Superterrane. The gabbro, gabbro–diorite, and series of gabbro and gabbro–diorite with high sodic alkalinity from the Dzhigdinskii Massif show obvious geochemical features of duality, including combination of intraplate and super-subduction origin. In this relation, we can assume that the origin of the gabbroids of the Dzhigdinskii Massif is related to the detachment of the oceanic lithosphere and its subduction into the mantle with the formation of an “asthenospheric window.” 相似文献
19.
Early paleozoic granitoids in the Lesser Khingan terrane, Central Asian Foldbelt: Age, geochemistry, and geodynamic interpretations 总被引：1，自引：0，他引：1
A. A. Sorokin A. B. Kotov E. B. Sal’nikova N. M. Kudryashov S. D. Velikoslavinskii S. Z. Yakovleva A. M. Fedoseenko Yu. V. Plotkina 《Petrology》2011,19(6):601-617
The U-Pb zircon dates obtained for the Sutara (480 ± 4 Ma), Kabalinskii (471 ± 10 Ma), and Durilovskii (461 ± 5 Ma) massifs
reliably confirm an Early Proterozoic orogenic event, which took place after granulite metamorphism at approximately 500 Ma
(Wilde et al., 2003) in the Lesser Khingan (Jiamusi) terrane. The rocks emplaced most shortly after the main metamorphic event
are the granites of the Sutara Massif and leucogranites of the Kabalinskii Massif, whose geochemistry is close to that of
collision granites. The quartz diorites and subalkaline granites of the Durilovskii Massif, whose geochemistry suggests their
origin in a postcollision environment with the participation of an enriched mantle source, were emplaced longer after metamorphic
event and after the aforementioned massifs. 相似文献
20.
对额尔古纳地块新元古代花岗岩进行了锆石LA-ICP-MS U-Pb年代学、岩石地球化学和锆石Hf同位素研究,以便对其新元古代岩浆作用历史与微陆块构造属性给予制约.所测花岗质岩石中锆石的CL图像特征和Th/U比值(0.17~1.46) 显示其为岩浆成因.测年结果并结合前人定年结果,可以判定额尔古纳地块上至少存在~929 Ma、~887 Ma、~850 Ma、~819 Ma、~792 Ma、~764 Ma和~738 Ma岩浆事件.岩石地球化学特征显示,~887 Ma花岗岩为一套后碰撞花岗岩类;而850~737 Ma花岗质岩石整体上属于A-型花岗岩,也有部分岩体(漠河、阿木尔、碧水和室韦岩体)显示I-型花岗岩特征.锆石Hf同位素特征反映这些花岗岩的源区既有中-新元古代(TDM2=884~1 563 Ma)新增生地壳物质的部分熔融,同时伴有少量古老地壳物质的混染,也有残留的古老中基性下地壳物质的部分熔融.综合研究区新元古代侵入岩的地球化学特征,同时对比新元古代全球构造热事件,认为额尔古纳地块上新元古代岩浆活动记录了Rodinia超大陆形成和演化过程中的地壳响应:927~880 Ma的岩浆作用应是Rodinia超大陆汇聚造山的产物;而850~737 Ma的岩浆作用应是对Rodinia超大陆快速裂解的记录.通过岩浆事件对比发现,额尔古纳地块与邻近的西伯利亚南缘微陆块(如中蒙古地块和图瓦地块)具有亲缘性,而与塔里木板块和华南板块至少在新元古代岩浆活动上具有一定的相似性,而明显区别于华北板块和西伯利亚板块. 相似文献