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白云鄂博矿田碳酸岩墙年代学再研究 总被引：9，自引：0，他引：9
白云鄂博地区发育侵入于白云鄂博群的碳酸岩墙。碳酸岩墙(00BYC19)中锆石的SHRIMPU-Pb下交点年龄为1984±180Ma,其ID-TIMS上交点年龄为2085±330Ma。碳酸岩墙(02BY80)中锆石SHRIMP的上交点年龄为2035±51Ma;02BY81中锆石的ID-TIMS上交点年龄为1934±64Ma。主矿北碳酸岩墙(00BYC21)的全岩Pb-Pb等时线年龄为1236±300Ma。本文及前人对白云鄂博地区的碳酸岩墙的定年结果表明该地区碳酸岩墙至少有两个阶段的侵入事件,第一阶段在2.0Ga左右,第二阶段在1.2Ga左右。前者是白云鄂博地区以至阴山地块北缘的一次主要的构造—岩浆事件,标志白云鄂博裂谷和白云鄂博群地层的形成。第二阶段的碳酸岩墙,代表白云鄂博裂谷在中元古代的活化,且与成矿有密切关系。 相似文献
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白云鄂博REE—Fe—Nb矿床酸岩墙锆石U—Pb年龄及其地质意义 总被引：10，自引：10，他引：10
对白云鄂博稀土 -铁 -铌矿矿区一火成碳酸岩内锆石 U - Pb年龄进行了测定 ,五颗锆石测定数据点拟合直线与谐合线的上交点年龄为 2 0 70± 33Ma,表明白云鄂博矿区火成碳酸岩脉的侵入时代最早可以追溯到早元古代 ,该年龄与矿区内正长岩和英云闪长岩锆石年龄等接近 ,构成了形成于裂谷环境的白云鄂博早元古代碱性岩 -碳酸岩杂岩体 相似文献
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对安徽铜陵新桥铜-硫-铁-金矿床区内的石英闪长岩和辉绿岩中的锆石分别进行了SHRIMP精确定年研究,石英闪长岩中锆石206Pb/238U年龄为(140.4±2.2)Ma,辉绿岩中锆石的年龄较复杂,其中发现了元古代锆石颗粒,其锆石207Pb/206Pb年龄为(2261±14)Ma,(1612±8)Ma,(919±12)Ma,(831±17)Ma。另外还有一组早古生代年龄的锆石,锆石206Pb/238U年龄为(443±13)Ma。以上这些新资料说明该区可能存在元古代基底的信息,且燕山期岩浆活动对本区成矿具有重要意义。 相似文献
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四川大陆槽稀土矿床碳酸岩-英碱正长岩锆石U-Pb年代学和Hf同位素性质及其地质意义 总被引：5，自引：2，他引：3
川西冕宁-德昌稀土成矿带是中国最重要的稀土成矿带之一,所有稀土矿床均与碳酸岩-正长岩杂岩体有关.前人研究表明,牦牛坪、木落寨和里庄碳酸岩-碱性杂岩体成岩年龄与其相应矿床的成矿年龄基本一致,而大陆槽正长岩年龄与REE矿床的成矿年龄相差甚远.本文对大陆槽碳酸岩、英碱正长岩进行了SHRIMP U-Pb锆石年代学和LA-MC-ICPMS锆石Hf同位素原位测量,它们的形成年龄分别为12.99±0.94Ma、14.53±0.31Ma,表明两者是同时形成的,且与其成矿年龄基本一致.碳酸岩和正长岩的εHf(t)值、Hf模式年龄与它们的εNd(t)值、Nd模式年龄所展现出来的特征一致,说明在其形成过程中有地壳物质的加入. 相似文献
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运用LA-ICP-MS U-Pb法,对位于东准噶尔卡姆斯特北部10 km处有争议的海相碎屑岩样品进行了U-Pb年龄测定,共测试碎屑锆石100颗,其中有效年龄数据点共90个。测试结果表明:(1)该套岩层的形成年龄可能为早石炭世。因为最年轻的谐和年龄为333.2 Ma,限定了该岩层的沉积下限。(2)该套岩层有多个物源区。碎屑锆石定年结果与区域岩浆热事件对比结果表明:早寒武世碎屑锆石(523.1 Ma、535.1 Ma)可能来自前人所述的准噶尔前寒武纪结晶基底,但有待进一步研究;中—晚奥陶世碎屑锆石(440.0 Ma、460.9 Ma)来自荒草坡群火山碎屑岩;早志留世碎屑锆石(429.3 Ma)可能来源于周边地区沉积的下志留统;中泥盆世碎屑锆石((371.5±2.5)Ma)来自卓木巴斯套组和乌鲁苏巴斯套组地层;早石炭世碎屑锆石((336.4±0.8)～(353.5±0.7)Ma)来自南明水组。(3)在测试的碎屑锆石中,有一颗锆石年龄为2 676.2 Ma,谐和度为99%,为可能存在前寒武纪古老结晶基底提供了一定的依据,但有待更进一步的证据。 相似文献
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青藏高原南羌塘基性岩墙群U-Pb和Sm-Nd同位素定年及构造意义 总被引：17，自引：0，他引：17
羌塘地区是青藏高原古特提斯研究的关键地区,羌塘南部地区基性岩墙群的侵位时代与构造背景对确定古特提斯阶段联合古陆解体的具体时间和青藏高原构造演化有重要意义。选择单颗粒锆石U-Pb法和全岩Sm-Nd等时线法对基性岩墙进行定年研究,获得了(312±4)Ma单颗锆石U—Pb谐合线年龄和(299±13)Ma和(314±5)Ma两个Sm-Nd全岩等时年龄。结合区域地质资料研究认为,基性岩墙群为羌塘地块裂离作用的产物,所获得的同位素年龄代表了基性岩墙群的侵位时间,为羌塘地块裂解提供了构造事件年龄,为重塑龙木错—双湖古特提斯洋盆的形成演化过程提供了重要信息。 相似文献
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滇西腾冲地块片麻状花岗岩的锆石U-Pb年龄 总被引：7，自引：1，他引：6
报道了滇西腾冲地块片麻状花岗岩的锆石U-Pb年龄。区域地质和岩相特征表明,片麻状花岗岩为岩浆成因,并经历了后期深熔作用。24颗锆石测得24个年龄数据中,1颗继承锆石的206Pb/238U年龄为537.5±5.6Ma,2颗岩浆锆石的206Pb/238U平均年龄为456Ma,3颗深熔锆石的206Pb/238U平均年龄为117Ma,18颗深熔锆石的Robust (Median) 206Pb/238U年龄为66.2+7/-4Ma。上述结果表明,花岗岩形成于早古生代,而后在白垩纪发生深熔作用,可能是特提斯演化过程中的岩浆响应。 相似文献
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大别-苏鲁造山带大理岩中榴辉岩包体的锆石有两种类型，为变质增生锆石和变质重结晶的残留碎屑锆石。变质增生锆石和完全变质重结晶锆石都具有较低的U、Th含量和Th/U比值，且给出两组变质年龄，分别为240.9±4.8~25.1±3.1 Ma和223.7±4.2~226.0±3.9 Ma。年龄为240.9±4.8~245.1±3.1 Ma的变质锆石的生长对应于板块俯冲过程中高压榴辉岩相变质作用期间的流体活动，而223.7±4.2~226.0±3.9 Ma的变质锆石的生长可能对应了板块折返早期的流体活动。这些年龄同样可以很好地用来限定其寄主大理岩的变质演化历史。 相似文献
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小秦岭-熊耳山地区岩墙锆石SHRIMP年代学研究——秦岭造山带岩石圈拆沉的证据 总被引：11，自引：6，他引：5
对小秦岭-熊耳山地区岩墙锆石开展了SHRIMP Ⅱ U-Pb法年代学研究显示,岩墙岩浆源区的锆石主要表现为华北南缘陆壳基底中的继承性锆石特征.根据地质关系确定的侵位于中生代花岗岩中的岩墙,其锆石年龄定年结果主要表现为1843±10Ma和768±15Ma左右的年龄,多数锆石表现为该区域熊耳群火山活动事件1850Ma左右的年龄,只有很少的锆石颗粒记录了中生代时期128Ma左右的侵位年龄.总体看来,岩墙中锆石较全面地记录了区域构造演化的历史.锆石测年结果反映出华北陆块阜平运动(2500～2400Ma)、华北南缘熊耳群火山喷发事件(1850Ma)、震旦纪构造活动(850～700Ma)、扬子陆块俯冲拼贴于华北南缘的造山事件(约200Ma)和燕山期(约130Ma)的岩墙岩浆侵位活动.岩墙的Sr、Nd、Pb同位素示踪揭示了岩墙岩浆源区与扬子陆块的亲缘性,从而证明新元古代-晚古生代时期扬子陆块向华北陆块南缘俯冲,以及后来秦岭造山带在造山期后华北南缘下地壳基底拆沉的地球动力学过程.岩墙中锆石测年结果多显示为老的继承性锆石的原因可能是中生代时期生长的锆石颗粒较小,而继承性锆石颗粒较大,锆石单矿物分选过程中主要挑选出继承性锆石的缘故. 相似文献
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《International Geology Review》2012,54(9):1629-1639
The deinocephalian pelvic girdle, of general pelycosaurian structure, is useful in systematic diagnosis. In primitive Russian deinocephalians, two contrasting pelvic patterns are recognized, one light, thin-walled, narrow, and of V-shaped cross-section, and the other massive, thick-walled, wide, and of U-shaped cross-section. The former is characteristic of two families of lightly- built, mobile land carnivores, the Eotitanosuchidae and the Brithopodidae. The Eotitanosuchidae are more primitive and pelycosaur-like, while the Brithopodidae show more variation, and specializations of large size, shallower acetabulum (related to mobility?), and re-enforcement of a weak pubic symphysis by additional processes. The massive type of pelvis characterizes large, heavily built herbivorous animals of the family Estemmenosuchidae. In general pelvic structure, the Estemmenosuchidae resemble the South African anteosaurs and tapinocephalians and the Russian tapinocephalians. In detail, however, they show a more primitive stage of evolution, overlaid by characteristic specializations which relate them more closely to the advanced Russian forms than to those of South Africa. Three new genera are erected, Biarmosaurus, fam. Eotitanosuchidae; Chthomaloporus, fam. Brithopodidae; and Molybdopygus, fam. Estemmenosuchidae. One specimen formerly referred to Deuterosaurus Yefremov 1954, and five formerly included in the type of Brithopus Yefremov 1954 are referred to Molybdopygus. The more primitive deinocephalians are from Yezhovo in the Ocher District, Perm Province, while more advanced forms are from Isheyevo, in Tataria, where-therocephalians and other South African elements are also found. It is therefore concluded that the Ochersk beds are older than those of Isheyevo and must be dated to zone I of Yefremov's system. — N. Hotton III. 相似文献
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《International Geology Review》2012,54(4):391-403
Detailed regional studies and the author' personal observations on tillite-like rocks in Siberia and Ural suggest that pseudo-tillites, only too common in subaqueous landslide formations, were often mistaken for tillites or tillite-like rocks, because of their resemblance to fossil moraines. --V. P. Sokoloff. 相似文献
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E.M. Lazko V.P. Kiriluk V.I. Lashmanov A.M. Lyssak A.A. Sivoronov G.M. Jatsenko 《Precambrian Research》1978,6(2):223-233
Soviet geologists consider the Precambrian to be divided into two groups — Archaean and Proterozoic; but such a division is unsatisfactory. A major unconformity separates Proterozoic volcanic and sedimentary formations from an underlying sequence that contains two supergroups of supercrustal formations. The oldest of these is unanimously considered to be Archaean. Rocks of that supergroup play an essential part in the composition of the Baltic, Ukrainian, Aldan and Anabar Shields and of the ancient fold belts of the East-European and Siberian platforms.Distinctive features in the composition, tectonic structure, metamorphism and metallogeny of Archaean complexes lead to the conclusion that they were formed in specifically mobile areas, different from geosynclinal areas.The other supergroup of high-grade metamorphic rocks has no clear place in the accepted two-fold stratigraphic scheme of the Precambrian, and it is considered sometimes to be Archaean and sometimes to be Early Proterozoic. We propose restoring the forgotten name “Eozoic” for that supergroup. Eozoic complexes are characterized by peculiarities of composition and inner structure, which signify changes in the tectonic regime of the earth at the lower and upper boundaries of the Eozoic Supergroup. These peculiarities give grounds for distinguishing the Eozoic Supergroup as an independent stratigraphic division.The Stanovoy Complex of the southern part of the Aldan Shield is a stratotype for the Eozoic Supergroup. Many well-known stratigraphic subdivisions of the Siberian Platform (e.g., the Eniseiskaya, the Birusinskaya series and others), the Taratash Complex of the Urals, the Goranskaya and Shahdarinskaya series of the South-West Pamir, the Tikitch complex and Aulskaya series of the Ukrainian Shield, and in part the Belomorsky Complex of the Baltic Shield, as well as some others, are also Eozoic.The Eozoic complexes are characterized by the following specific features: only some supercrustal formations are typical for them; the small number of rock types which have a total thickness about 5–6 km; relatively monotonous mineral composition of the rocks; variable quantitative ratios of rocks; absence of contrasting marker beds; regional metamorphism and ultrametamorphism in the amphibolite facies; wide development of ultrametamorphic granitoids and migmatites; distinct tectonic differentiations of the basin of sedimentation.Dates determined by isotopic analyses, which mostly reflect the metamorphism of the deposits, fall predominantly in the range 2600–3100 Ma. 相似文献
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International Journal of Earth Sciences - 相似文献
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《International Geology Review》2012,54(1):23-26
On October 12, 1962, a joint session of the Presidium of the U.S.S.R. Academy of Sciences and the Collegium of the U.S.S.R. Ministry of Geology and Mineral Reserves adopted a resolution “On the present state of the geological sciences in the U.S.S.R. Academy of Sciences and the U. S. S. R. Ministry of Geology and Mineral Reserves and their prospects for the future.” Important contributions of Russian geologists are acknowledged, but attention is drawn to many shortcomings. Future goals of geological study and work are given in detail. Twenty-one lines of research to be concentrated on are given, covering all phases of geology, geophysics, and geochemistry. In discussing the failings of the geological profession in Russia, it is of interest to note the following comment: “Geological research in other countries is still insufficiently studied and applied, and we are not making adequate use of geologic information from abroad.” The list of the Russian geologists' shortcomings sounds vaguely familiar. —J. R. Hayes 相似文献
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《International Geology Review》2012,54(10):1756-1770
The Pacific Mobile belt is differentiated into an outer (continental) zone of predominantly Mesozoic folding (Verkhoyansk -Chukotka, Mongolo-Okhotsk, and Sikhote-Alin folded provinces) and an inner oceanic zone of Cenozoic folding, adjacent to mobile provinces of the "island arc" type (Sakhalin, the Kuriles, Kamchatka). These zones are separated by the East-Asian volcanic belt associated with a fault system which cuts off the older Mesozoic Verkhoyansk-Chukotka and Sikhote- Alin structures. Two important mineralization epochs are evident - Sino-Cambrian and late Mesozoic- Cenozoic. The Mesozoic-Cenozoic mineralization epoch exhibits a definite tendency for “rejuvenation” of the mineralization processes, going away from the continent and toward the Pacific trough, from late Jurassic in the eastern Trans-Baykal region and parts of the northeast to Neogene in the province of the Okhotsk geosynclines. An outstanding feature of endogeneous mineralization in this region is the linear arrangement of the ore zones determined by a system of major magma-controlling and other faults.—C. E. Sears 相似文献
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Selenium was determined in duplicate portions from three bottles of six U.S.G.S. standard rocks by a spect rofluorimetric procedure. The following averages, as p.p.m. Se, were obtained: PCC-1, 0.031; GSP-1, 0.088; BCR-1, 0.12; SCo-1, 0.91; MAG-1, 1.3; and SGR-1, 3.7. One-way analysis of variance of the several sets of data showed no significant differences in the selenium content among bottles of any specific rock; these samples may be accepted as homogeneous for their selenium contents by this analytical method. 相似文献