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新疆库鲁克塔格南华系砂岩碎屑组成对其物源及盆地演化的指示 总被引:1,自引:0,他引:1
库鲁克塔格南华系记录了塔里木北缘同期的火山-沉积事件和蚀源区物质组成及演化的信息。该区不同剖面内南华系各组砂岩碎屑组分的统计分析显示,贝义西组砂岩在不同剖面内组成差异显著:西山口剖面以岩屑砂岩为主,且岩屑为火山岩岩屑与沉积岩岩屑,物源为再旋回地层,而依格孜塔格剖面以长石砂岩和岩屑长石砂岩为主,岩屑主要为变质岩岩屑,物源为下伏古元古代高级变质岩。砂岩碎屑组成在剖面上垂向的变化表明贝义西组沉积期与照壁山组沉积期间(725 Ma±)存在一个沉积转型事件,导致贝义西组之上的照壁山组、阿勒通沟组及特瑞艾肯组砂岩组成在不同区域趋于一致,转变为代表基底隆起-过渡大陆区物源的典型“长石砂岩”。南华系砂岩碎屑组成与大陆裂谷盆地沉积砂岩相似,且物源区存在由前裂谷地层-过渡裂谷肩部-切割裂谷肩部-克拉通内部的连续演化过程,是库满凹陷早期裂解的岩相学记录。 相似文献
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库鲁克塔格地区是土什布拉克组的命名地和典型剖面分布区,主要由灰绿色砂岩及粉砂岩组成。运用LA-ICP-MS U-Pb方法,对土什布拉克组3件砂岩碎屑锆石进行U-Pb年龄测定,共获得了183组U-Pb有效年龄,既限定了地层的最早形成时代,同时又获取研究区早古生代的演化资料。获得14个较年轻锆石年龄表明,土什布拉克组形成于中—晚志留世。碎屑锆石的谐和年龄表明,物源主要集中在422~537 Ma、559~999 Ma、1018~1574Ma和1604~2498Ma。碎屑锆石年龄394~537Ma和CL图像揭示,在早古生代时期发育大量岩浆岩,但目前地表仅有少量的岩浆岩记录。研究区新元古代的岩浆锆石年龄值,可能与罗迪尼亚超大陆的聚合-裂解有关。碎屑锆石也表明研究区发育区域变质作用,部分与哥伦比亚超大陆有关。 相似文献
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The Early-Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks.However,their provenance has been scarcely studied since it was named.Geochemistry of clastic rocks was commonly used to interpret the provenance.Detrital heavy mineral analyses help frame the U-Pb age from zircon grains,integrated with geochemical data from detrital tourmaline and spinels.These techniques were used to characterize components of the sediment flux and define erosion areas in the Qurugtagh block,further providing evidence about the tectonic evolution of the South Tianshan and Tarim plate.The maximum depositional age constrained by detrital zircon dating was Early-Middle Devonian.Multiple diagrams for sedimentary provenance using major and trace elements indicate that continental island arc-related felsic rocks were the major source rocks for the Shugouzi Formation.Detrital tourmalines are dravite and schorl.The results of detrital tourmaline electron probe microanalysis(EPMA)show that the source rocks are mainly metasedimentary rocks and granitoids.The detrital chromian spinels within the sediments are characterized by high chroumium(Cr#)and varying magnesium(Mg#).The discrimination plots reveal that these spinels were sourced from island arc magmatic rocks.The laser ablation inductively-coupled plasma mass spectrometry(LA-ICP-MS)U-Pb chronology of detrital zircons suggests that the sediments were derived mainly from 414-491 Ma and 744-996 Ma magmatic rocks.Paleocurrent restoration,sandstone geochemistry,EPMA,and detrital zircon geochronology indicate that the source rocks were predominantly derived from Late Ordovician and Devonian magmatic rocks and subordinately from recycled Neoproterozoic magmatic rocks.Comprehensive analyses of the source areas suggest that a remnant arc still existed in the Early Devonian and the Shugouzi Formation was deposited in a passive continental margin. 相似文献
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库鲁克塔格地区新元古代沉积物源分析:来自碎屑锆石年代学的证据 总被引:6,自引:2,他引:4
库鲁克塔格位于南天山和塔里木盆地接合部,保留相对较完整的地层记录。新元古代贝义西组主要为一套火山-沉积组合序列,育肯沟组为浊流成因的砂岩和粉砂岩组合。对取自两个地层的沉积岩样品,分别进行了碎屑锆石LA-ICP-MS U-Pb测年,并分别获得了93组和71组U-Pb有效年龄。其中贝义西组锆石U-Pb年龄主峰值为821Ma、次峰值为861Ma的碎屑锆石(761~847Ma)具有显著优势,育肯沟组年龄值为768Ma(次峰值为800Ma和741Ma)的碎屑锆石比较集中,说明库鲁克塔格地区在741Ma、768Ma、800Ma、821Ma和861Ma有大规模的岩浆活动。10个太古代碎屑锆石年龄以及综合已有的研究成果,确认库鲁克塔格存在中-新太古代基底。贝义西组砂岩主要源自761~847Ma、851~972Ma和1808~2498Ma岩石。育肯沟组主要来自734~845Ma、858~963Ma和1708~2486Ma的岩石。 相似文献
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位于亚洲中部的塔里木克拉通是中国三大古老克拉通之一,经历了新元古时期罗迪尼亚(Rodinia)大陆聚合和裂解。然而,关于塔里木在该时期的构造演化仍然存在较多争议。本文对塔里木北缘库鲁克塔格地区南华系地层中流纹岩及伴生的正长花岗岩开展岩石学、地球化学、锆石U-Pb年代学和Hf同位素研究,结果表明:正长花岗岩与流纹岩是一套具有"时、空、源"一致的花岗质火山-侵入杂岩组合,锆石U-Pb年龄分别为735±10 Ma和738.9±5.4 Ma,同为新元古代南华纪岩浆作用的产物。它们具有高硅(69.85%~73.87%)、低铁(2.36%~2.96%)、贫镁(0.16%~0.75%)和富碱(Na2O+K2O=7.51%~9.05%)的特征,属碱性系列、过铝质岩石。富集K、Rb、Th等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ba、Sr、P和Ti等。具A2型花岗岩的特点,是俯冲挤压向减压伸展构造转换背景下岩浆活动的产物。锆石Hf同位素组成较均一, εHf(t)值大多为-17.4~-10.6之间,其二阶段模式年龄TDM2为2732~2321 Ma,表明岩浆来源于太古宙-元古宙古老结晶基底。结合前人研究表明,大约在735 Ma塔里木北缘开始进入减压伸展的拉张环境,之后可能发生了Rodinia超大陆的裂解。 相似文献
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Neoproterozoic Volcanic Rocks in the Southern Quruqtagh of Northwest China:Geochemistry,Zircon Geochronology and Tectonic Implications 总被引:1,自引:0,他引:1
The Early Neoproterozoic Beiyixi Formation volcanic rocks of the southern Quruqtagh comprise mainly of a suite of tholeiitic basalts,alkaline andesites,and calc-alkaline rhyolites.The rhyolites are characterized by variably fractionated enrichment in light rare earth elements(LREE) and flat in heavy rare earth elements(HREE),and strongly negative Eu anomalies.Compared to the rhyolites,the andesites also exhibit enrichment in LREE and flat HREE(chondrite-normalized values of La/Yb,and La/Sm are 13.30-41.09,3.18-6.89 respectively).Their rare earth element patterns display minor negative Eu anomalies.Both of them exhibit coherent patterns with strongly to moderately negative anomalies of Nb,Zr,Ti,and Hf on spider diagrams.Two rhyolite and one andesite magmatic zircons with defined oscillatory zoning yielded weighted mean 206Pb/238U ages of 743±7 Ma,741±2 Ma,and 727±4 Ma.These ages are interpreted to represent the timing of volcanic eruptions. According to geochemistry and rock type,these volcanic rocks formed within a continental island-arc environment following subduction of the oceanic crust during the Early Neoproterozoic period. 相似文献
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