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1.
《Chemie der Erde / Geochemistry》2019,79(1):94-112
To constrain the tectonic evolution of the eastern segment of the Paleo-Asian Ocean, we conducted zircon U–Pb-Hf dating and whole-rock geochemical analyses for metasedimentary rocks from the Dongnancha Formation in the Huadian area in central Jilin Province, Northeastern (NE) China. Most detrital zircons from the metasedimentary rocks display clear oscillatory zoning and striped absorption in cathodoluminescence (CL) images and have Th/U ratios of 0.1–1.8, thus indicating a magmatic origin. U–Pb isotopic dating using LA-ICP-MS method for zircon samples from the metasedimentary rocks reveals that the depositional age can be constrained to the period between 250 and 222 Ma. Geochemical data reveal low to intermediate degrees of weathering of the source material and compositionally low to intermediate maturity. Detailed analyses of detrital zircon U–Pb-Hf geochronology and geochemistry show that these metasedimentary rocks are derived from a bidirectional provenance. The predominant derivation is from Permian–Early Triassic felsic-intermediate igneous rocks of central Jilin Province and adjacent regions in the northern margin of the North China Craton, although felsic-intermediate igneous rocks and continental material in the eastern segment of the Central Asian Orogenic Belt from the Cambrian–Carboniferous represent additional sources and minor amounts of Paleoproterozoic–Neoproterozoic material have been input from the North China Craton. A number of geochemical indicators and tectonic discrimination diagrams collectively indicate a continental island arc-active continental margin setting for the deposition of the protoliths of the metasedimentary rocks. The results of geochemical and geochronological analyses of the provenance and tectonic setting of the metasedimentary rocks indicate that the Dongnancha Formation was likely deposited in an intermountain basin in a post-orogenic fast uplift setting, suggesting that the final closure of the eastern segment of the Paleo-Asian Ocean in the Huadian area of central Jinlin Province likely occurred between the Early Triassic and Middle Triassic. 相似文献
2.
秦岭造山带东段秦岭岩群的年代学和地球化学研究 总被引：20，自引：14，他引：6
对东秦岭地区的陕西省洛南县、宁陕县、长安县和河南省淅川县出露的四个秦岭岩群变质岩进行的岩石学和地球化学研究表明,样品主要由变质火山岩和变质沉积岩组成.详细的锆石U-Pb定年结果显示三个正变质岩均形成于新元古代早期(971～843Ma),而副变质岩中富集大量新元古代碎屑锆石,根据最年轻的谐和年龄(859Ma)和早古生代的变质年龄,推测其沉积时代为新元古代中晚期.因此,北秦岭南部的秦岭岩群的变质岩主要由新元古代早期的火成岩和新元古代中晚期的沉积岩组成.变质作用主要发生在加里东期,局部有燕山期的变质作用叠加.指示北秦岭的造山作用主要发生在早古生代.岩石地球化学研究还显示秦岭岩群的新元古代火山岩均形成于火山弧构造环境,沉积岩沉积于大陆弧-活动大陆边缘环境,指示秦岭造山带在新元古代早期是一个火山弧.秦岭岩群的火山岩和沉积岩在形成时代和构造环境方面与扬子克拉通西缘的特征非常相似,表明位于北秦岭造山带的秦岭岩群应归属于扬子克拉通陆块,是扬子北缘的一个大陆边缘弧. 相似文献
3.
在扬子板块西缘断续分布有多套变质沉积岩系,厘定区内不同岩石单元的时代对于探讨扬子西缘的构造演化具有重要意义。本文对出露于扬子板块西缘米易垭口地区的五马箐组变沉积岩以及侵入其中的片麻状黑云二长花岗岩体进行了锆石LA-ICP-MS U-Pb定年和Lu-Hf同位素分析。结果表明:区内五马箐组的沉积时代介于1.19~1.01Ga,其地层归属为会理群而非康定群,位于五马箐组之下的“冷竹关组”并非变沉积地层而是一套片麻状黑云二长花岗岩体。五马箐组碎屑锆石年龄存在~1.56Ga、~2.50Ga两个主要峰值以及~1.43Ga、~1.68Ga、~1.87Ga、~2.32Ga、~2.68Ga五个次要峰值,推断其物质来源主要为扬子板块西南缘的撮科杂岩、隐伏的或还暂未发现的太古代基底岩石、同时期岩浆岩和早期变沉积岩的再循环。碎屑锆石的ε_(Hf)(t)值在~1.7Ga发生了显著变化,暗示扬子板块西缘的构造体制由陆壳汇聚向裂谷活动转变,且在~1.56Ga处于裂谷岩浆活动的峰期。花岗岩体正的ε_(Hf)(t)值反映出扬子板块西缘在~1.0Ga有一次新生陆壳生长事件,可能是格林威尔造山后的伸展塌陷构造背景下裂谷岩浆活动的产物。 相似文献
4.
Depositional Age,Provenance Characteristics and Tectonic Setting of the Ailaoshan Group in the Southwestern South China Block 总被引：1，自引：0，他引：1
The depositional and metamorphic ages and provenances of the Ailaoshan(ALS) Group in the Ailaoshan-Red River(ALS-RR) shear zone, southwestern South China Block(SCB), were investigated to constrain the tectonic history of the southwestern SCB. In this study, we use petrology, geochemical analysis, zircon cathodoluminescence imaging and UPb geochronology to analyse samples of quartzite, garnet-bearing two-mica schist and metapelite. The age spectra of detrital zircon grains from these metasediments show two dominant age peaks at 550–424 Ma and 876–730 Ma and two subordinate peaks at 970–955 Ma and ～2450 Ma. The youngest peak, corresponding to the early Palaeozoic, accounts for more than 20% of the total dates and constrains the deposition of the ALS Group to the Palaeozoic rather than the Palaeoproterozoic as traditionally thought. Moreover, two peaks of metamorphic ages corresponding to the Permo-Triassic and Cenozoic were also identified, and these ages document the tectonothermal events associated with the Indosinian collision between the Indochina Block and the SCB and the Himalayan collision between the Indian and Asian plates. Geochemical data suggest that the provenances of the ALS Group were dominated by continental arc and recycled metasedimentary rocks. The comparison of probability density distribution plots of the detrital zircon U-Pb age data indicates that the Neoproterozoic detritus in the ALS Group was probably derived from the arc-related Neoproterozoic intrusive bodies in the northwestern and southwestern SCB. Furthermore, the early Palaeozoic detritus might have been sourced from eroded early Palaeozoic strata and magmatic plutons in Cathaysia and volcanic rocks in the western Indochina Block. 相似文献
5.
《International Geology Review》2012,54(16):2036-2056
ABSTRACTThe Chinese Southwest Tianshan Orogenic Belt is located along the boundary between the Central Asian Orogenic Belt (CAOB) and the Tarim Block (TB), NW China. It records the convergence of the Tarim Block and the Middle Tianshan, and is, therefore, a crucial region for understanding the Eurasia continental growth and evolution. The Wulagen (geographical name) metasedimentary rocks of the Wuqia area (mainly metamorphic sandstones and mica schists) form one of the metamorphic terranes in the Southwestern Tianshan Orogenic Belt. The geochronology of these rocks is poorly known, which hampers our understanding of the tectonic evolution of the belt. We analyzed 517 zircon grains for detrital zircon U–Pb dating and 93 zircon grains for in situ Lu–Hf isotopic compositions from the Wulagen metasedimentary rocks. The analyzed zircon grains yield Neoarchean to late Paleozoic U–Pb ages with major age peaks at ~2543 Ma, 1814 Ma, 830 Ma, 460 Ma, and the youngest cluster of zircon (magmatogene) ages is 395 Ma. The zircon U–Pb data show that the late Paleozoic (Early Devonian) is the maximum depositional age of the Wulagen metasedimentary rocks, rather than the previously considered Precambrian period. The zircons with Paleozoic ages yield εHf(t) values of ?22.0 to +11.3 and two-stage model ages (TDM2) of 3.95 to 1.30 Ga, suggesting that the parental magmas were formed from partial melting of pre-existing crustal rocks. Our zircon U–Pb geochronology and Hf isotopic data indicate the major source regions for the Wulagen metasedimentary rocks was the Kyrgyzstan North Tianshan. The zircon age population of 600–400 Ma (peak at ~460 Ma) has negative εHf(t) values (?15.0 to ?0.6) and Mesoproterozoic two-stage model ages, suggesting that the early Paleozoic magmatism resulted mainly from the melting of ancient crust, which played an important role in crustal evolution in the southern CAOB. 相似文献
6.
华夏陆块早古生代沉积记录对于了解华南陆块在Gondwana超大陆演化过程中所起的作用具有重要意义。本文对广东省中山市神湾地区下寒武统八村群开展了锆石年代学和元素地球化学研究。结果表明,八村群变泥质粉砂岩的碎屑锆石年龄可分为4034~3122 Ma、2765~2250 Ma、1765~1443 Ma、1126~901 Ma、884~773 Ma以及595~547 Ma六组,其中最年轻的一组碎屑锆石加权平均年龄将该地层的最大沉积时间限定在551±4 Ma。锆石的Hf同位素特征则指示八村群沉积物源可能以古老地壳物质再循环为主,伴少量初生地壳物质。八村群变粉砂岩和变泥岩样品的化学风化指数(CIA)和成分成熟度(ICV)分别为79. 8~86. 4和0. 39~0. 87,均表明源区经历了相对强烈的化学风化作用。元素地球化学结果显示,八村群样品强烈富集不相容元素,而亏损Ni、Cr和Co等,指示八村群源区可能以活动大陆边缘构造背景下的长英质岩石为主。综合对比八村群与世界其他陆块同时期沉积地层的碎屑锆石年龄组成,本文认为八村群代表了新元古代晚期至早古生代早期Gondwana超大陆聚合过程中造山作用的沉积响应,支持华夏陆块位于Gondwana超大陆北缘,靠近北印度板块和羌塘地体,是该超大陆的重要组成部分。 相似文献
7.
中条山绛县群碎屑锆石LA-ICP-MS U-Pb测年及其地质意义 总被引：5，自引：2，他引：3
中条山位于山西省的南缘,主要由涑水杂岩、绛县群、中条群、担山石群和西阳河群组成.其中绛县群主要由变质的砂岩、半泥质岩、泥质岩、碳酸岩和火山岩组成.在取自绛县群的两个变质沉积岩样品中,利用LA-ICP-MS定年方法,获得85个单颗粒碎屑锆石,锆石年龄主要介于2416～2899Ma之间,样品05ZR02-1中的主峰值年龄为约2667Ma,样品05YQ12-1中的主峰值年龄为约2537Ma,表明这些变质沉积岩主要源于华北克拉通中部带,以晚太古代老地壳物质为主.在这些碎屑锆石中,最年轻的年龄为2160±17Ma,可代表其沉积时的最大年龄,绛县群变质沉积岩的的沉积作用应该发生在2200Ma之后,而不是在晚太古代后的2.5～2.3Ga,绛县群与北峪花岗岩之间并不是呈现侵入接触关系. 相似文献
8.
Qiugen Li Shuwen Liu Zongqi Wang Zhuyin Chu Biao Song Yanbin Wang Tao Wang 《International Journal of Earth Sciences》2008,97(3):443-458
Detrital zircon U–Pb ages, whole-rock Nd isotopic, and geochemical data of metasedimentary rocks from the Wutai Complex in
the Central Zone, North China Craton, have been determined. Compositionally, these rocks are characterized by a narrow variation
in SiO2/Al2O3 (2.78–3.96, except sample 2007-1), variable Eu anomalies, spanning a range from significantly negative Eu anomalies to slightly
positive anomalies (Eu/Eu* = 0.58–1.12), and positive ε
Nd (t) values (0.1–1.97). The 18 detrital zircons of one sample yielded age populations of 2.53 Ga, 2.60 Ga, and 2.70–2.85 Ga.
Geochemical data reveal intermediate source weathering, varying degrees of K-metasomatism in the majority of these metasedimentary
rocks, whereas other secondary disturbances seem to be negligible. Detailed analysis in detrital zircon U–Pb geochronology,
whole-rock Nd isotope, and geochemistry shows that these metasedimentary rocks are derived from a mixed provenance. The predominant
derivation is from the late Archean granitoids and metamorphic volcanics in the Wutai Complex, and there is also input of
older continental remnants, except TTG gneisses, from the Hengshan and Fuping Complexes. The sediments were probably deposited
in fore-arc or/and intra-arc basins within an arc system. 相似文献
9.
北祁连榴辉岩相变沉积岩的特征及其构造意义 总被引：1，自引：0，他引：1
在北祁连造山带中,出露典型的高压/低温变质岩石,前人对其中的低温榴辉岩已做过较多的研究,但对其中的变沉积岩研究涉及很少.本文展示了榴辉岩相变质沉积岩的岩石学、地球化学、锆石U-Pb年代学和Hf同位素方面的一些新的研究结果.变沉积岩含有榴辉岩相的矿物组合,峰期温压条件为t= 450～520℃,p=1.9～2.3 GPa,与相邻榴辉岩的温压条件一致.地球化学显示这些岩石的原岩为不成熟的沉积岩,可能形成于大陆边缘或大陆岛弧环境.变沉积岩中的碎屑锆石U-Pb年龄主要集中在1800 Ma左右和540～600 Ma之间,结合锆石Hf同位素特征,表明其原岩的碎屑来源既有周缘陆块的前寒武纪变质基底物质,又有新元古代-早古生代新生洋壳或增生物质.同时,这些数据也表明北祁连早古生代洋壳俯冲过程中发生了活动大陆边缘的构造剥蚀作用,即形成于上盘的沉积物(弧前盆地或增生楔)被构造作用运移到俯冲带中,并俯冲到60～70km深处,遭受榴辉岩相变质作用,然后折返到地表. 相似文献
10.
兴蒙造山带南缘早古生代增生造山带内是否存在陆壳一直缺少直接证据,制约了对增生带结构及演化的认识.在达茂旗东北部兴蒙造山带南缘增生带内识别出一套原地的变质地层,野外观察及锆石U-Pb年代学、Hf同位素地球化学研究表明,该套地层形成时代为中元古代晚期,可能代表了增生造山带内的古老地壳.地层的碎屑锆石峰值年龄集中于~1.8 Ga,并具有~3.0 Ga、~2.8 Ga、~2.5 Ga、~1.6 Ga等次级峰值,与华北北缘白云鄂博、化德、狼山群等地层碎屑锆石年龄组成一致;表明其应为华北陆块的一部分,物源则主要来自于华北克拉通内部不同时代地质体的剥蚀.该套地层的识别及其与华北陆块的亲缘性表明,早古生代兴蒙造山带南缘增生带内存在陆壳,构造环境上应为古亚洲洋向华北克拉通俯冲形成的活动陆缘;同时,其与车根达来构造带的关系显示后者并非蛇绿岩,更可能为弧后伸展引起的超基性岩对陆壳的侵入形成. 相似文献
11.
LI Qiu-gen LIU Shu-wen WANG Zong-qi ZHANG Jian DANG Qing-ning WANG Yue-ran WANG Tao 《矿物岩石地球化学通报》2008,27(Z1)
The geochemical and Sm-Nd isotopic compositions of Palaeoproterozoie metasedimentary rocks from the Jiangxian and Zhongtiao Groups, distributed in the Zhongtiao Mountains in the North China Craton, have been carried out in order to evaluate the provenance, and tectonic setting of the sedimentary basin. 相似文献
12.
《Journal of South American Earth Sciences》2010,30(4):784-804
Metamorphosed volcano-sedimentary rocks accreted to the northern South American continental margin are major vestiges of the Caribbean oceanic plate evolution and its interactions with the continent. Selected whole rock geochemistry, Nd–Sr isotopes and detrital zircon geochronology were obtained in metabasic and metasedimentary rocks from the Santa Marta and San Lorenzo Schists in northernmost Colombia. Trace element patterns are characterized by primitive island arc and MORB signatures. Similarly initial 87Sr/86Sr-εNd isotopic relations correlate with oceanic arcs and MORB reservoirs, suggesting that the protoliths were formed within a back-arc setting or at the transition between the inta-oceanic arc and the Caribbean oceanic crust. Trace element trends from associated metasedimentary rocks show that the provenance was controlled by a volcanic arc and a sialic continental domain, whereas detrital U/Pb zircons from the Santa Marta Schists and adjacent southeastern metamorphic units show Late Cretaceous and older Mesozoic, Late Paleozoic and Mesoproterozoic sources. Comparison with continental inland basins suggests that this arc-basin is allocthonous to its current position, and was still active by ca. 82 Ma. The geological features are comparable to other arc remnants found in northeastern Colombia and the Netherland Antilles. The geochemical and U/Pb detrital signatures from the metasedimentary rocks suggest that this tectonic domain was already in proximity to the continental margin, in a configuration similar to the modern Antilles or the Kermadec arc in the Pacific. The older continental detritus were derived from the ongoing Andean uplift feeding the intra-oceanic tectonic environment. Cross-cutting relations with granitoids and metamorphic ages suggest that metamorphism was completed by ca. 65 Ma. 相似文献
13.
The Mongol–Okhotsk Belt, a major structural element of East Asia, is probably the youngest orogenic segment within the Central Asian Orogenic Belt. However, the timing of final closure of the Mongol–Okhotsk Ocean remains unresolved. Here, we present detrital zircon U–Pb–Hf isotopic data and whole-rock geochemical data (major and trace elements and Sm-Nd isotopes) for the metasedimentary rocks from the Un'ya–Bom Terrane, Dzhagdy Terrane, and the eastern part of the Tukuringra Terrane. Our new zircon U-Pb ages suggest that all sedimentary formations along the Dzhagdy Transect are early Mesozoic in age, rather than Paleozoic as previously thought. The detrital zircons from the metasedimentary rocks in the Un'ya–Bom Terrane, the Dzhagdy Terrane, and the eastern part of the Tukuringra Terrane yielded the youngest concordant ages of 194 ± 4, 193 ± 2, and 171 ± 2 Ma, respectively. Moreover, we note that the so-called sedimentary formations of these terranes are not single sedimentary sequences as previously suggested, but a set of an olistostrome or tectonic mélanges composed of rocks of different ages and origins. These sedimentary formations are probably relics of the Mongol–Okhotsk remnant basin that formed in the “gaps” between the southern margin of the North Asian Craton and the Amur Block during their collision. The absence of detrital zircons younger than 171 Ma in the sedimentary rocks of the Mongol–Okhotsk basin implies that the final closure of this basin could have taken place at the boundary of the Early and Middle Jurassic as a result of the collision or the development of the Mongol–Okhotsk orogenic belt in this region. After that, the Mongol–Okhotsk Belt underwent intense deformation related to within-plate strike-slip faulting, which could be attributed to the late Mesozoic rotation of the North Asian Craton relative to the continental massifs of East Asia. 相似文献
14.
《Precambrian Research》2001,105(2-4):331-356
The Paleoproterozoic Lower Aillik Group is a deformed metasedimentary–metavolcanic succession located in the Makkovik Province of Labrador, eastern Canada. The group is situated near the boundary between reworked Archaean gneiss of the Nain (North Atlantic) craton and juvenile Paleoproterozoic crust that was both tectonically accreted and formed on or adjacent to this craton during the ca. 1.9–1.78 Ma Makkovikian orogeny. The Lower Aillik Group is structurally underlain by Archaean gneiss and structurally overlain by ca. 1860–1807 Ma bimodal, dominantly felsic volcanic and volcaniclastic rocks of the Upper Aillik Group. We present geochemical data from metavolcanic rocks and U–Pb geochronological data from several units of the Lower Aillik Group in order to address the depositional and tectonic history of this group. U–Pb data were obtained using both thermal ionization mass spectrometry (TIMS) and laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS). Two quartzite units near the structural base of the Lower Aillik Group contain detrital zircons only of Archaean age, and are interpreted to have been deposited on the Nain craton during post-2235 Ma rifting and initiation of a passive continental margin. Overlying mafic metavolcanic rocks contain thin horizons of intermediate tuff, one of which is dated at 2178±4 Ma. This relatively old age, and an inferred stratigraphic relationship with underlying sedimentary units, suggest that the volcanic rocks represent transitional oceanic crust, consistent with their geochemical similarity to tholeiitic rifted margin sequences of Mesozoic age in eastern North America. A package of interlayered psammitic and semipelitic metasedimentary rocks that appears to stratigraphically overlie the mafic volcanic unit is dominated by Paleoproterozoic detrital zircons but also contains Archaean grains. This package was deposited after 2013 Ma, the age of the youngest concordant zircon. The U–Pb data imply a minimum 165 m.y. time gap between mafic volcanism and sedimentation, and are consistent with deposition of the psammite–semipelite unit in an evolving foredeep that heralded the approach of a Paleoproterozoic arc terrane. Accretion of this terrane to the Nain cratonic margin at ca. 1.9 Ga initiated the Makkovikian orogeny. Although the Lower Aillik Group is highly deformed and may contain internal tectonic boundaries or be incomplete, the U–Pb and geochemical data allow quantitative assessment of a prolonged rift-drift-basin closure cycle that characterized the Early Paleoproterozoic evolution of the southern Nain cratonic margin. 相似文献
15.
Paleoproterozoic orogens of the North Australian Craton are related to the assembly of the Columbia Supercontinent. The roles of the distinct orogens in the Paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure. The age and isotopic systematics of detrital zircon grains hosted in Paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton, in terms of paleogeography and tectonic setting. The oldest (Early Paleoproterozoic) metasedimentary units are characterised by detrital zircon ages peaking at ca. 2500 Ma. The zircon εHf values show large variations in the different orogens and range from −18 to +6. The overlaying youngest turbiditic units show minor accumulation of Archean detritus. Units from apparently different metasedimentary sequences have a major detrital zircon age population at ca. 1865 Ma, and a relatively restricted range of zircon εHf values between −7.3 and +2.6. The isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment, probably due to horst-graben architecture of the early Paleoproterozoic basin. The youngest turbiditic units blanketed this early horst-graben architecture and in part have a local provenance. Potential detritus sources include South Australian Craton, Dharwar Craton and Aravalli-Lesser Himalayan terrains in India, South China, and Madagascar (Africa). This finding indicates that these regions might have been connected before the Columbia Supercontinent was formed. The ubiquitous ca. 2500 Ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called Kernorland. In addition, the data do not support a proximity of the North Australian Craton with the North China Block, Western Laurentia (North America), and Kaapvaal Craton (Africa) during Columbia amalgamation. 相似文献
16.
Y. Kawano M. Akiyama T. Ikawa B.P. Roser T. Imaoka J. Ishioka M. Yuhara T. Hamamoto Y. Hayasaka H. Kagami 《Gondwana Research》2006,9(1-2):126
Pre-Cretaceous metasedimentary rocks occurring in the Inner Zone of the Southwest Japan Arc can be divided into three major groups, namely, high P/T metamorphic (Renge and Suo belts), low P/T metamorphic (Hida-Oki, Ryoke and Higo belts), and accretionary terranes (Akiyoshi, Maizuru, Mino-Tamba, and Ashio belts). Major and trace element compositions of most of the sedimentary rocks are typical of relatively mature sedimentary rocks, although abundances of ferromagnesian elements also suggest the presence of a significant mafic to intermediate igneous component. The sedimentary rocks with older Nd model ages (> 2.0 Ga) have high εSr values and major and trace element geochemical signatures typical of mature sediments, whereas those with younger model ages (< 1.45 Ga) have low εSr values and immature geochemical characteristics. With the exception of Hida samples, the sedimentary rocks from other districts have geochemical and isotopic features intermediate between the rocks with old and young Nd model ages. Some of the Hida samples have old Nd model ages, but others are influenced by younger rock fragments and have immature geochemical features. Based on combined isotopic and geochemical evidence, Inner Zone sedimentary rocks with older Nd model ages are interpreted to have been derived from felsic upper continental crustal materials such as Sino-Korean or northwest Yangtze craton granitoids. Compositions of rocks with younger Nd model ages reflect addition of mafic to intermediate detritus, such as island arc basalts and andesites. The rocks with intermediate Nd model ages may have formed in and around the Asian continental margin. The Hida metasedimentary rocks may have been derived from several terranes of varying age and geochemical composition. 相似文献
17.
S. D. Velikoslavinskii A. B. Kotov V. P. Kovach E. V. Tolmacheva A. M. Larin A. A. Sorokin A. P. Sorokin K. L. Wang E. B. Salnikova 《Doklady Earth Sciences》2016,468(2):545-548
The results of Sm–Nb isotopic–geochemical studies of metasedimentary and metavolcanic rocks of the Dzheltulak Group of the central part of the Dzheltulak suture, as well as geochronological U–Th–Pb (LA ICP MS) studies of detrital zircons from metasedimentary rocks, which are considered as Paleoproterozoic in current stratigraphic schemes, are presented. The age of the youngest zircons is 170–190 Ma, whereas the age of the last stage of regional metamorphism is 140–150 Ma. Thus, the Dzheltulak Group hosts metasedimentary rocks, the age of the protolith of which ranges from 140–150 to 170–190 Ma. The detrital zircons derived from intrusive and metamorphic rocks of the Selenga–Stanovoi and Dzhugdzhur–Stanovoi superterranes. 相似文献
18.
佳疙瘩组变碎屑岩地球化学特征及古构造环境 总被引：8，自引：0，他引：8
内蒙古额尔古纳地区佳疙瘩组变碎屑岩的主量元素以富集SiO2、Al2O3、K2O、Na2O等为特征，微量元素以富含高场强不相容元素为特征。岩石的地球化学特征表明其原岩为一套陆源碎屑岩。沉积环境为被动大陆边缘。沉积盆地性质为被动大陆边缘拉张（早期）和弧后拉张（后期）两种深部背景下的拉张断陷盆地。而基性岩浆的侵入活动代表这一过程的持续和进一步发展。 相似文献
19.
中国西秦岭碎屑锆石U-Pb年龄及其构造意义 总被引：5，自引：1，他引：4
西秦岭是北接华北克拉通、西接祁连与柴达木、南接松潘—甘孜地块的东秦岭造山带的西延。文中研究了该区从前寒武纪到三叠纪的碎屑沉积岩。这些碎屑沉积岩中分离出的锆石由LA-ICPMS(激光剥蚀等离子体质谱)进行了U-Pb定年。全岩Nd亏损地幔模式年龄类似于扬子克拉通年龄,主要分布于1.55~1.98Ga,峰值为1.81Ga,而与华北克拉通主要为古元古代与太古宙的模式年龄形成明显的对比。泥盆系中的碎屑锆石930~730Ma的U-Pb年龄指示其与扬子克拉通具亲缘性。930~730Ma是源区地壳的强烈增长阶段。二叠系—三叠系的碎屑沉积岩主体以含老于1600Ma的碎屑锆石为特征。碎屑锆石U-Pb年龄与Sm-Nd同位素组成指示此时华北克拉通南缘的基底岩石成为二叠系—三叠系碎屑沉积岩的重要物源。扬子克拉通在三叠纪时与华北克拉通拼接。西秦岭二叠系—三叠系碎屑沉积岩含有高达50%的华北克拉通南缘的基底岩石。 相似文献
20.
扬子克拉通北缘碎屑沉积岩地球化学特征及意义 总被引：3，自引：0，他引：3
通过系统研究扬子克拉通北缘西乡-碑坝小区后太古代变质沉积岩的主量元素、微量元素和Nd同位素组成, 得出如下结论: (1) 扬子北缘中、晚元古代三花石组杂砂岩的εNd(t), 分别为+2.72和+0.69, TDM分别为1.40Ga和1.57Ga, 与扬子北缘同时期西乡群火山岩具有相近的Nd同位素组成, 扬子克拉通北缘新元古代存在的岛弧物质控制着该区中、晚元古代沉积物源的地球化学组成, 后河群碎屑物质对火地垭群沉积岩有一定的影响; (2) 扬子克拉通北缘古生代沉积物源区以再旋回沉积物源为主, 并随时间变化对再旋回沉积物源的接受逐渐加强, 沉积源区的长英质物质逐渐增多, 分异程度越来越高; 西乡-碑坝小区从寒武纪-志留纪沉积物源很可能是扬子克拉通基底崆岭群和基性火山岩等风化剥蚀后混合的产物, 本区从晚泥盆世开始, 其沉积物源区与秦岭群片麻岩的风化剥蚀有明显的关系; (3) 扬子北缘西乡-碑坝小区从晚二叠世到早侏罗世碎屑沉积岩的εNd(t) 比早古生代碎屑沉积岩的明显偏大, 结合微量元素数据分析, 这与晚二叠世峨眉山玄武岩的多次喷发(火山灰) 和风化剥蚀作用有关. 相似文献