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1.
新疆准噶尔古生代洋盆闭合时限——来自卡拉麦里地区石炭纪碎屑锆石U-Pb年代学的约束 总被引：4，自引：0，他引：4
新疆准噶尔古生代洋盆闭合时限对中亚造山带古生代构造格局及演化研究具有重要意义。东准噶尔卡拉麦里断裂带南缘广泛出露石炭纪陆相粗碎屑岩系,沉积相分析表明其形成于扇三角洲沉积环境。依据区域地层对比、岩石组合特征及地层接触关系,将其重新厘定为山梁砾石组。选择西段滴水泉和东段双井子2个地区的山梁砾石组剖面进行地层对比,并在2个剖面底部采集粗砂岩样品进行LA-ICP-MS锆石U-Pb年龄测定,获得最年轻的碎屑锆石年龄分别为349±4Ma和355±3Ma,代表山梁砾石组沉积时代晚于349Ma,应为早石炭世早期。碎屑锆石年龄分布特征及砾石成分表明,其物源主要来自断裂带北侧的泥盆纪火山岩。在分析前人资料的基础上,认为山梁砾石组碎屑岩系是卡拉麦里造山带强烈隆升造山过程的沉积学响应,形成于前陆盆地,限定了准噶尔古生代洋盆闭合时限在早石炭世早期之前。 相似文献
2.
柴达木盆地石炭系是中国北方新区新层系油气勘探调查研究的热点,盆地东部地区石炭系出露较全,但多数学者认为柴东地区不存在二叠系。针对扎布萨尕秀组归属于石炭纪还是二叠纪的争议,采集扎布萨尕秀组的砂岩碎屑锆石开展了U-Pb LA-ICP-MS同位素测年,获得40个和谐年龄分布在2488±34 Ma至288±3 Ma之间,最年轻的一组碎屑锆石的加权平均年龄288.0±2.0 Ma（MSWD=0.112,n=21）。这意味着该扎布萨尕秀组中的砂岩沉积于288 Ma之后,晚于国际石炭—二叠纪界限（299 Ma）。依据野外调查和已有研究成果,扎布萨尕秀组中赋存丰富的虫筳科化石,其中膨胀型虫筳属Pseudoschwagerina或Sphaeroschwagerina的出现是进入二叠纪的重要标志。结合碎屑锆石年代学和虫筳属化石特征,扎布萨尕秀组应归属早二叠世,说明柴达木东部地区存在二叠纪沉积记录。该认识为深化柴达木盆地晚古生代—中生代沉积建造和构造演化提供了重要的地层学证据。 相似文献
3.
F. Bastida C. Brime S. García-López G. N. Sarmiento 《International Journal of Earth Sciences》1999,88(1):38-48
The palaeotemperature distribution in the transition from diagenesis to metamorphism in the western nappes of the Cantabrian
Zone (Somiedo, La Sobia and Aramo Units) are analysed by conodont colour alteration index (CAI) and illite crystallinity (IC).
Structural and stratigraphic control in distribution of CAI and IC values is observed. Both CAI and IC value distributions
show that anchizonal conditions are reached in the lower part of the Somiedo Unit. A disruption of the thermal trend by basal
thrusts is evidenced by CAI and IC values. There is an apparent discrepancy between the IC and CAI values in Carboniferous
rocks of the Aramo Unit; the IC has mainly anchizonal values, whereas the CAI has diagenetic values. Discrepant IC values
are explained as a feature inherited from the source area. In the Carboniferous rocks of the La Sobia Unit, both IC and CAI
indicate diagenetic conditions. The anchimetamorphism predated completion of emplacement of the major nappes; it probably
developed previously and/or during the early stages of motion of the units. Temperature probably decreased when the metamorphosed
zones of the sheets rose along ramps and were intensely eroded. In the context of the Iberian Variscan belt, influence of
tectonic factors on the metamorphism is greater in the internal parts, where the strain and cleavage are always present, than
in the external parts (Cantabrian Zone), where brittle deformation and rock translation are dominant, with an increasing role
of the burial on the metamorphism.
Received: 11 May 1998 / Accepted: 19 January 1999 相似文献
4.
华北板块北缘呼兰群~(40)Ar-~(39)Ar定年及其构造意义 总被引：2，自引：2，他引：0
呼兰群发育于华北板块北缘,主要为一系列长英质火山岩和沉积岩组成的受到低绿片岩相-角闪岩相变质作用和多期变形作用改造的变质岩系,分布于吉林中部红旗岭-呼兰镇一带。大部分地区的呼兰群地层层序被严重破坏,野外观察的"层理"实际上是构造置换作用形成的构造面理,绝大多数的岩性界面为构造接触。呼兰群由一系列相互叠置的构造岩片构成,具有构造混杂岩性质。呼兰群经历了两期韧性变形作用:早期受到NNE-SSW向挤压作用,呼兰群表现为由NNE向SSW逆冲的运动学特征;晚期可能受到NE-SW向伸展作用,主要表现为由SW向NE倾向滑移的运动学特征。本次分别对采自红旗岭地区强变形带的白云石英片岩、石榴白云片岩中的白云母进行40Ar-39Ar测年,分别获得220.23±2.15Ma、221.31±2.6Ma的坪年龄,认为~220Ma年龄应代表华北板块北缘碰撞造山带造山后伸展作用发生的时间。 相似文献
5.
内蒙古阿拉善北部好比如地区下石炭统好比如组时代修订及其地质意义 总被引：1，自引：0，他引：1
内蒙古阿拉善北部好比如地区地层研究程度较低,好比如组时代久有争议,制约了该区地层层序、沉积建造及构造演化的深入研究。测得好比如地区原定为早石炭世的好比如组碎屑岩LA-ICP-MS锆石U-Pb最小峰值年龄为279Ma,火山岩LA-ICP-MS锆石U-Pb年龄为270.3±2.2Ma,时代应修订为早二叠世空谷期—中二叠世罗德期。结合区域上岩性特征、地层对比及锆石年龄谱对比,将好比如组中段修订为船山统隆林阶—罗甸阶埋汗哈达组(P1-2m),将其上段修订为阳新统祥播阶—冷坞阶阿其德组(P2a)。好比如组的时代修订为研究区晚古生代地层层序、沉积建造及构造演化的研究提供了新的依据。 相似文献
6.
7.
Dominique Gasquet Gilles Levresse Alain Cheilletz Moulay Rachid Azizi-Samir Abdellah Mouttaqi 《Precambrian Research》2005,140(3-4):157-182
New geochronological analyses (U–Pb SIMS zircon ages) have yielded ages of 552 ± 5 Ma for the Bou Madine rhyolitic dome (Ougnat, eastern Anti-Atlas), 543 ± 9 Ma for the Tachkakacht rhyolitic dyke (Saghro–Imiter, eastern Anti-Atlas), and 531 ± 5 Ma for the Aghbar trachytic sill (Bou Azzer, central Anti-Atlas). Inherited zircon cores from the Aghbar trachytic sill and from the Bou Madine rhyolitic dome have been shown to be of Statherian age (ca. 1600–1800 Ma) and Palæoproterozoic (>2100 Ma) age, respectively, suggesting that a significantly older protolith underlies the Pan-African rocks in the Central and Eastern Anti-Atlas. Granodiorites and rhyolites from the Saghro–Imiter area have similar low 87Sr/86Sr (0.702–0.706) and 143Nd/144Nd (0.5116–0.5119) initial ratios, suggesting a mixture of mantle and lower crust sources. This can also be inferred from the low 187Os/188Os ratios obtained on pyrite crystals from the rhyolites.A recently published lithostratigraphic framework has been combined with these new geochemical and geochronological data, and those from the literature to produce a new reconstruction of the complex orogenic front that developed at the northern edge of the Eburnian West African craton during Pan-African times. Three Neoproterozoic magmatic series can be distinguished in the Anti-Atlas belt, i.e., high-K calc-alkaline granites, high-K calc-alkaline to shoshonitic rhyolites and andesites, and alkaline-shoshonitic trachytes and syenites, which have been dated at 595–570, 570–545 and 530 Ma, respectively.The accretion of the Pan-African Anti-Atlas belt to the West African super continent (WAC) was a four-stage event, involving extension, subduction, moderate collision and extension. The calc-alkaline magmatism of the subduction stage was associated with large-scale base metal and gold mineralisation. Metallogenic activity was greatest during the final extensional stage, at the Precambrian–Cambrian boundary. It is characterised by world-class precious metal deposits, base–metal porphyry and SEDEX-type occurrences. 相似文献
8.
滇西南涧—云县一带广泛出露的无量山岩群是一套与三江特提斯造山带密切相关的中低变质沉积岩夹火山岩系,其形成时代、沉积充填序列及大地构造属性一直存在争议。出露于南涧县公郎乡一带的无量山岩群发育有厚数厘米的变质英安岩夹层。对变质英安岩进行LA-ICP-MS锆石U-Pb定年,分别获得428.7±8.7Ma的岩浆结晶年龄和338～387Ma、250.5±8.1Ma、146.0±6.0Ma的变质年龄。认为无量山岩群原始沉积岩形成于志留纪,在古特提斯洋俯冲过程中,经历古生代造弧而发生区域变质作用,在白垩纪受热事件影响而发生热变质作用;同时还获得2034±22Ma、1140±16Ma、731±15Ma及469～522Ma的单颗粒锆石年龄,这些年代峰值与整个扬子陆块西缘获得的前寒武纪、古生代构造热事件年龄及分布特征基本可以对比;记录了Columbia、Rodinia和Gondwana超大陆的形成与裂解过程。 相似文献
9.
The Northwestern Ordos Terrane (NOT) in the Western North China Craton (W-NCC) comprises the northwestern Ordos Basin in the east and the eastern Alxa Massif in the west, bound by the Helanshan Tectonic Belt (HTB). The key position makes the NOT crucial for understanding the evolutionary processes of the W-NCC and particularly the tectonic relation of the Alxa Massif with the W-NCC. In this study, petrologic, stratigraphic and geochronologic studies were conducted on Permo-Carboniferous successions in the NOT. Stratigraphic correlation reveals that Carboniferous marine successions display a transgressive sequence with a slight westward-deepening facies variation, evidenced by the continuous onlap of tidal-flat layers toward the east. The Permian nonmarine strata in the HTB and the Ordos Basin have no substantial facies variation, defining an upward regressive sequence from deltaic to fluvial associations, while time-equivalent units in the eastern Alxa Massif have been eroded. The generally SSW-directed paleocurrents suggest that Permo-Carboniferous siliciclastic materials were derived from a highland to the northeast. The unified sedimentary system in the NOT constrains the Alxa Massif to be part of the W-NCC. The Lower Carboniferous sandstone contain zircons with a concentrated age cluster of 1700–2700 Ma, comparable to Archean to Paleoproterozoic crystalline basement in the northern W-NCC. By contrast, in addition to zircons of 1700–2700 Ma, Late Carboniferous and Permian sandstones all contain abundant Paleozoic zircons with two age clusters around ~300 Ma and ~420 Ma, which are similar to age patterns of Paleozoic magmatism in the northern W-NCC. Zircon age profile and sandstone modal composition indicate the origin from an Andean-type continental arc. The Permo-Carboniferous tectono-sedimentary processes of the NOT should occur in a marginal basin behind the continental arc along the northern W-NCC in response to the southward subduction of Solonker Ocean, southern branch of Paleo-Asian Ocean. 相似文献
10.
Variscan geodynamic evolution of the Carnic Alps (Austria/Italy) 总被引：1，自引：1，他引：1
The South-Alpine Carnic Alps are part of the southern flank of the European Variscides and display a continuous sedimentary record from Late Ordovician to Devonian times followed by Carboniferous S-directed nappe stacking and Late Carboniferous to Early Permian post-collisional collapse. The tectonometamorphic and sedimentary evolution of the Carnic Alps resembles a continuous process where pre- and syn-orogenic volcanism, syn-orogenic flysch sedimentation, deformation including nappe stacking, metamorphism and tectonic collapse shift in age from internal zones in the N towards external zones in the S. New structural, petrological and sedimentological data are presented concerning the tectonometamorphic history of the Carnic Alps. We distinguish three thrust sheets or tectonic nappes differing in their stratigraphic, sedimentological, deformational and metamorphic histories which were thrust over each other in Carboniferous times. Our data lead to a new geodynamic model showing an evolution from rifting or back-arc spreading in the Late Ordovician to the establishment of a mature passive continental margin in the Late Devonian/Early Carboniferous, flysch sedimentation in an active continental margin setting during the Visean/Namurian and finally collision during the Late Carboniferous between the northern margin of Gondwana and a microcontinent to the N. 相似文献
11.
《Gondwana Research》2014,25(3-4):1038-1050
The New England Orogen of easternmost Australia is dominated by suites of Palaeozoic to earliest Mesozoic rocks that formed in supra-subduction zone settings at Gondwana's eastern margin. On the northern New South Wales coast at Rocky Beach, Port Macquarie, a serpentinite mélange carries rare tectonic blocks of low-grade, high-pressure, metamorphic rocks derived from sedimentary and igneous protoliths. Dominant assemblages are glaucophane + phengite ± garnet ± lawsonite ± calcite ± albite blueschists and lawsonite-bearing retrogressed garnet + omphacite eclogites. In some blocks with sedimentary protoliths, eclogite forms folded layers within the blueschists, which is interpreted as Mn/(Mn + Fe) compositional control on the development of blueschist versus eclogite assemblages. Review of previous studies indicates pressure–temperature conditions of 0.7–0.5 GPa and ≤ 450 °C. Three samples of high-pressure metasedimentary rocks contain Archaean to 251 ± 6 Ma (Permo-Triassic) zircons, with the majority of the grains being Middle Devonian to Middle Carboniferous in age (380–340 Ma). Regardless of age, all grains show pitting and variable rounding of their exteriors. This morphology is attributed to abrasion in sedimentary systems, suggesting that they are all detrital grains. New in situ metamorphic zircon growth did not develop because of the low temperature (≤ 450 °C) of metamorphism. The Permo-Triassic, Devonian and Carboniferous zircons show strong heavy rare earth element enrichment and negative europium anomalies, indicating that they grew in low pressure igneous systems, not in a garnet-rich plagioclase-absent high pressure metamorphic environment. Therefore the youngest of these detrital zircons provides the maximum age of the metamorphism. A titanite + rutile porphyroblast within an eclogite has a U–Pb age of 332 ± 140 Ma (poor precision due to very low U abundances of mostly < 1 p.p.m.) and provides an imprecise direct age for metamorphism. In the south of the Port Macquarie area, the Lorne Basin ≥ 220 Ma Triassic sedimentary and volcanic rocks unconformably overlie serpentinite mélange, and provide the minimum age of the high-pressure metamorphism. Our preferred interpretation is that the 251 Ma zircons are detrital and thus the Port Macquarie high-pressure metamorphism is constrained to the end of the Permian–Early Triassic. Emplacement of the serpentinite mélange carrying the Rocky Beach high-pressure rocks might have been due to docking of a Permian oceanic island arc (represented by the Gympie terrane in southern Queensland?) and an Andean-style arc at the eastern Australian margin (expressed in the New England Orogen by 260–230 Ma north-south orientated magmatic belts). Alternatively, if the 251 Ma grains are regarded as having grown in thin pegmatites, then the dominant Devonian–Carboniferous detrital population still indicates a maximum age for the high pressure metamorphism of ca. 340 Ma. A ≤ 340 Ma age of metamorphism would still be much younger than the previously suggested ca. 470 Ma (Ordovician) age, which was based on Ar–Ar dating of phengites. 相似文献
12.
A. Zeh M. A. Cosca H. Brätz M. Okrusch M. Tichomirowa 《International Journal of Earth Sciences》2000,89(1):52-71
40 Ar/39Ar–mica and 207Pb/206Pb–zircon dates are presented and combined with existing P–T data and the sedimentary record. These data indicate that the
RCC was faulted into three segments which underwent different exhumation histories during the Late Carboniferous/Early Permian.
The eastern segment shows 40Ar/39Ar–biotite data of336 ±4 and 323±3 Ma. Furthermore, it is intruded by the Thuringian Hauptgranite dated at 337±4 Ma by the
207Pb/206Pb single zircon method. At approximately 300 Ma rocks of the eastern segment were finally exposed and, subsequently, subsided
as part of the Oberhof pull-apart basin, filled by Late Carboniferous/Early Permian molasse sediments and volcanic rocks (296–285 Ma;
Goll 1996). A similar Late Carboniferous evolution is inferred for the western segment, since it is also overlain by Upper
Carboniferous volcanic rocks. In contrast to the eastern and western segments, distinctly younger intrusion and cooling ages
were recorded for the central segment of the RCC (40Ar/39Ar muscovite: 311±3 Ma; 40Ar/39Ar biotite: 293–288±3 Ma) that was intruded by the Trusetal Granite, the Ruhla Granite and Brotterode Diorite (207Pb/206Pb single zircon: 298±2, 295±3, 289±4 Ma, respectively). These young data are unique in the MGCR and testify that plutonic
activity and cooling of basement rocks took place simultaneously with basin formation and volcanism in the eastern and western
segments. Overlying Upper Permian (Zechstein) and Triassic sediments indicate final exposure of the central segment by approximately
260 Ma, as a part of the Ruhla-Schleusingen Horst. Combination of these results with P–T data from the contact aureole of
the Trusetal granite indicate that the central segment was unroofed by at least 8.5 km during the Late Carboniferous. The
Late Carboniferous/Early Permian horst-basin formation, documented in the RCC, is due to dextral transtensional movements
along the NW-trending Franconian fault system. It may have been enhanced by mantle upwelling widespread in Central Europe
during the Early Permian that also caused intensive magmatism in the Thuringian Forest region.
Received: 2 February 1999 / Accepted: 15 November 1999 相似文献
13.
滇黔桂地区晚古生代浅水碳酸盐岩台地与深水硅泥质盆地共存的古地理格局,是在加里东期褶皱基底上发生裂陷及差异沉降而发展起来的。广西宜州—柳州一带既是晚古生代上扬子碳酸盐岩地台南缘1条重要的沉积相分界线,也是晚古生代桂中和桂北地层分区、古生代—中生代雪峰山南段构造体系和桂中坳陷构造体系的分界线。文中通过对宜山—柳州一带晚古生代地层的区域对比和成因分析,恢复了桂中宜山—柳州地区晚古生代沉积盆地的演化历史。狭长型宜州裂陷槽盆地西起丹池断裂,向东经龙头、北牙、宜州延伸至柳州。自中泥盆世开始,首先在东西两端开始裂陷下沉,至早石炭世发展成型。受北侧来自江南隆起带陆源碎屑物质充填影响,其表现为南北不对称并在早石炭世晚期被填平。在宜州裂陷槽内发育多处早石炭世沉积型碳酸锰矿,含矿地层分布、地层序列及其沉积背景明显与裂陷槽演化有关。它们既是盆地演化历史的见证,也体现了桂中地区裂陷海槽的特色,值得在后续锰矿成因研究中予以重视。 相似文献
14.
Evolution of Yizhou aulacogen in Guangxi during Late Paleozoic and distribution of manganese deposits in Early Carboniferous 
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下载免费PDF全文 The palaeogeographic configuration of the shallow water carbonate platform and deep water siliceous basin formed in the Yunnan-Guizhou-Guangxi region during the Late Paleozoic,which developed on the rifting of fold basement and differential subsidence during the Caledonian period. Yizhou-Liuzhou in Guangxi is an important sedimentary boundary in the southern Upper Yangtze carbonate platform. It is also the stratigraphic boundary of Late Paleozoic between middle and northern Guangxi,and it is the tectonic boundary between the southern Xuefengshan and central Guangxi depression during Paleozoic and Mesozoic. In this paper,the evolution of sedimentary basin located at Yishan-Liuzhou region during the Late Paleozoic is reconstructed through the regional stratigraphic correlation and genetic analysis.The elongate Yizhou rifting belt develops from the Nandan-Hechi fault from the west,and extends along Longtou,Beiya,Yizhou,and to Liuzhou. The rifting started at the eastern and western ends of the narrow rifting belt during the Middle Devonian and it developed into the rifting basin during the Early Carboniferous. Due to massive terrestrial siliciclastic filling derived from the Jiangnan Uplift to north,the rifting basin presented the asymmetrical feature and it was eventually filled up at late Early Carboniferous. Many magnesium deposits of Early Carboniferous are found in the rifting basin of Yizhou. The distribution of ore-bearing strata,the depositional succession and sedimentary environment are obviously related with the evolution of rifting basin. They are the evidences of basin evolution,implying the characteristics of rifting aulacogen in central Guangxi,which should be paid more attention in the manganese ore genesis study. 相似文献
15.
The Neoproterozoic Anti-Atlas belt (Morocco) is a key segment in tracing the history of the northern margin of the West African craton (WAC) from Rodinia breakup to Gondwana assembly. In order to constrain geodynamic events related to rifting and convergence and their stratigraphic records, a radiometric study was carried out on the volcano-sedimentary Tachdamt and Bleïda Formations. The volcaniclastic deposits of Tachdamt Fm. yield an age of ca. 883 Ma and provide a new constraint for the timing of the subaqueous volcanic eruption and the initiation of rifting in the Anti-Atlas. This age is ~100 my older than the previous age of 788 ± 10 Ma obtained from Rb/Sr isotope dating (Clauer, 1976). Available zircon data from the interbedded clastic deposits from Tachdamt Fm. indicate major shifts in provenance during the rifting with sediments sourced from the WAC and a nearby Grenvillian terrane. Detrital zircon ages from metasiltstones of Bleïda Fm. set a maximum depositional age at ca. 700 Ma. The age spectra discloses a major shift in sediment input with provenance from the WAC, Grenvillian terrane and an arc-related terrane (ca. 770–700 Ma) lying along the Anti-Atlas margin. The newly obtained results combined with existing radiometric data allowed the refinement of the stratigraphic and geotectonic framework of the pre-Pan-African strata in the WAC. The Early Tonian syn-rift volcanism has much in common with similar events in other cratons and provides a stratigraphic record for incipient Rodinia breakup. The overlying Bleïda Fm. deposited in a peripheral foreland basin chronicles the Cryogenian arrival of the ca. 770–700 Ma Bou Azzer-Siroua arc-related terrane at the Anti-Atlas margin, and correlates with initial accretion in West Gondwana. The new results indicate that the Grenvillian detrital input in the Anti-Atlas during both geodynamic stages points toward a possible Mesoproterozoic terrane existing along the western margin of the WAC. 相似文献
16.
In this paper we discuss the timing of final closure of the Paleo-Asian Ocean based on the field investigations of the Carboniferous–Permian stratigraphic sequences and sedimentary environments in southeastern Inner Mongolia combined with the geology of its neighboring areas. Studies show that during the Carboniferous–Permian in the eastern segment of the Tianshan-Hinggan Orogenic System, there was a giant ENE–NE-trending littoral-neritic to continental sedimentary basin, starting in the west from Ejinqi eastwards through southeastern Inner Mongolia into Jilin and Heilongjiang. The distribution of the Lower Carboniferous in the vast area is sparse. The Late Carboniferous or Permian volcanic-sedimentary rocks always unconformably overlie the Devonian or older units. The Upper Carboniferous–Middle Permian is dominated by littoral-neritic deposits and the Upper Permian, by continental deposits. The Late Carboniferous–Permian has no trace of subduction-collision orogeny, implying the basin gradually disappeared by shrinking and shallowing. In addition, it is of interest to note that the Ondor Sum and Hegenshan ophiolitic mélanges were formed in the pre-Late Silurian and pre-Late Devonian respectively, and the Solonker ophiolitic mélange formed in the pre-Late Carboniferous. All the evidence indicates that the eastern segment of the Paleo-Asian Ocean had closed before the Late Carboniferous, and most likely before the latest Devonian (Famennian). 相似文献
17.
内蒙古苏尼特左旗地区位于兴蒙造山带中段,是研究古生代俯冲-增生造山作用和地壳生长的关键地区。在苏尼特左旗南部,晚泥盆-早石炭世色日巴彦敖包组角度不整合在早古生代增生楔之上,已有研究对于其沉积环境、盆地属性及区域构造意义一直存在较大分歧。本文对色日巴彦敖包组敖木根呼都格剖面和阿拉塔特剖面碎屑岩和火山岩夹层开展锆石UPb测年及Hf同位素分析,并进行了沉积相分析进一步查明了地层层序、时代及物源特征,并对沉积环境和盆地属性进行了探讨。研究表明,敖木根呼都格剖面色日巴彦敖包组底部含砾粗砂岩最小谐和碎屑锆石年龄为391±5Ma,中下部凝灰质砂岩最小谐和碎屑锆石年龄为338.2±4.3Ma,凝灰岩锆石年龄为336±2Ma、333±3.5Ma,结合古生物化石,表明底部形成于晚泥盆世,中上部地层形成于早石炭世晚期。阿拉塔特剖面中上部安山质火山碎屑岩最小谐和碎屑锆石年龄加权平均值为320.4±6.2Ma,表明其形成于晚石炭世。碎屑锆石年龄谱及Hf同位素组成表明底部及中部砂岩碎屑物主要来自近源的早古生代白音宝力道和二连东乌旗地区弧岩浆岩,少量来自北侧南蒙古弧。结合沉积相分析,推测苏尼特左旗南部色日巴彦敖包组下部为一套形成于弧陆碰撞后被动陆缘滨浅海相沉积建造,中上部为形成于弧前盆地的一套杂砂岩夹火山岩建造。以上资料表明,该区从早石炭世开始转为活动陆缘背景,暗示古亚洲洋中东段在晚古生代仍未封闭。 相似文献
18.
范国清 《沉积与特提斯地质》1990,10(3):1-8
1986—1989年,作者参与了辽宁石炭二叠纪岩相古地理研究专题工作,其间曾赴河南、山西等地考查、学习,积累了中朝板块东部的一些资料,现对研究区石炭纪的沉积特征、古构造、古地理及海侵等有关问题讨论如下(按石炭系三分;由于山西组的时代尚有争论,本文只讨论石炭系本溪组(群)和太原组)。一、区域地质背景本文讨论范围包括吉南、辽东(南)、山东、河北、山西、河南、苏皖及朝鲜半岛北部等中朝板块东部地区。近年来,中朝板块的前寒武纪杂岩中测得超过3400Ma的放射性年龄资料已达14件(王东方,1986),说明其不仅是我国也是全球最古老的地块之一。其上的 相似文献
19.
内蒙迪彦庙地区早二叠世寿山沟组地层发育良好,岩性相对稳定,变质、变形程度较低,是研究区范围内早二叠世地层层序研究的理想地区。该课题逐层实测了寿山沟组剖面,从剖面的岩性地层人手,着重分析了迪彦庙地区早二叠世的岩性组合特征、基本层序、沉积旋回特征;同时根据古生物化石类型和组合,推断该区域形成的地质时代和沉积环境。研究表明：寿山沟组剖面厚度为9598．98m,根据岩性和粒度的大小,可分3个岩段：一段为滨浅海一浅海陆棚沉积;二段、三段为一套浊流沉积岩系,发育特征性浊流沉积构造,为典型的复理石建造。 相似文献
20.
D. Hoy G. Rosenbaum R. Wormald U. Shaanan 《Australian Journal of Earth Sciences》2013,60(8):1109-1124
The southern part of the New England Orogen exhibits a series of remarkable orogenic bends (oroclines), which include the prominent Z-shaped Texas and Coffs Harbour oroclines. The oroclines are defined by the curvature of Devonian–Carboniferous forearc basin and accretionary complex rock units. However, for much of the interpreted length of the Texas Orocline, the forearc basin is mostly concealed by younger strata, and crops out only in the Emu Creek Block in the eastern limb of the orocline. The geology of the Emu Creek Block has hitherto been relatively poorly constrained and is addressed here by presenting new data, including a revised geological map, stratigraphic sections and new detrital zircon U–Pb ages. Rocks of the Emu Creek Block include shallow-marine and deltaic sedimentary successions, corresponding to the Emu Creek and Paddys Flat formations, respectively. New detrital zircon U–Pb data indicate that these formations were deposited during the late Carboniferous and that strata were derived from a magmatic source of Devonian to Carboniferous age. The sedimentary provenance and detrital zircon age distribution suggest that the sequence was deposited in a forearc basin setting. We propose that the Emu Creek and Paddys Flat formations are arc-distal, along-strike correlatives of the northern Tamworth Belt, which is part of the forearc basin in the western limb of the Texas Orocline. These results confirm the suggestion that Devonian–Carboniferous forearc basin rocks surround the Texas Orocline and have been subjected to oroclinal bending. 相似文献