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1.
Here we present the results of U–Pb LA–ICP–MS dating of detrital zircons from the Ediacaran–Early Cambrian deposits of the eastern part of the Baltic monoclise (Leningrad Region). The obtained age spectra of the detrital zircons suggest that, in the Ediacaran–Early Cambrian, the main clastic material source to the northwest of the Russian Platform was the Baltic Shield. Then in the Early Cambrian along with the Baltic Shield provenance, a clastic source from the Timanian margin of Baltica (northeast in modern coordinates) contributed to the deposits. The obtained data either somewhat set limits of the Timanian orogen formation as older than the previously suggested Middle Cambrian (about 510 Ma), based on the “absence of a Proto–Uralian–Timanian provenance signal” in the Sablino Formation rocks in the south Ladoga, or suggest another rearrangement of detritus transportation paths at the end of Stage 3 (Atdabanian).  相似文献   

2.
The results of LA–ICP–MS U–Pb analyses of detrital zircons from the Precambrian deposits of Luga–Ladoga monocline are discussed. The age spectra of the zircons separated from the Riphean to Upper Vendian sandstones from the Shotkusa-1 well demonstrate dominance of the Paleo- and Mesoproterozoic grains while the Archaean zircons are subordinate. The Riphean debris sources were local swells of the Northern Ladoga basement. The sequence interval presumably corresponding to the Vasilieostrov Formation (Upper Vendian) has yielded not only Paleo- and Mesoproterozoic zircon ages, but Neoproterozoic as well, implying a Timanide provenance: these zircons (527 ± 9 and 516 ± 13 Ma) allow deposition of a significant part of the Shotkusa-1 sequence at the very beginning of the Cambrian.  相似文献   

3.
The first U?Pb dates are obtained for detrital zircons from Upper Precambrian deposits of the Sredni (Zemlepakhtinskaya and Kuyakan formations) and Rybachi (Lonskii Formation) peninsulas. The spectra of ages of detrital zircons in sandstone samples from the Zemlepakhtinskaya and Kuyakan formations are similar to a significant extent to each other, which implies the dominant role of the same provenances. Most zircon grains are the Paleoproterozoic and Mesoproterozoic in age; some of them are characterized by Mesoarchean and Neoarchean ages. Zircons dated back to 1.0?2.0 Ga with maxima at approximately 1.8, 1.5, 1.3, and 1.1 Ga are the most abundant. The youngest zircon grains are the Mesoproterozoic in age: 1050 ± 21Ma (i.e., close to the Mesoproterozoic?Neoproterozoic boundary) and 1028 ± 21 Ma from the Zemlepakhtinskaya and Kuyakan formations, respectively. The distribution spectrum of ages obtained for zircons from sandstones of the Lonskii Formation significantly differs from that characteristic of zircons from sandstones of the Zemlepakhtinskaya and Kuyakan formations. The zircon population from the Lonskii Formation is dominated by detrital zircons with Neoarchean and Paleoproterozoic ages (2.8?1.6 Ga); Paleoarchean and Mesoarchean grains are scarce. Their age maxima are registered at levels of approximately 2.7 and 1.8 Ga. The minimum age obtained for zircons from sandstones of the Lonskii Formation (1349 ± 35 Ma) allows the Rybachi block to be considered as being older as compared with the Sredni bock. Crystalline complexes of the Baltic Shield served as a main provenance for the Upper Precambrian deposits of the peninsulas under consideration. The dates obtained for detrital zircons from the Upper Precambrian deposits of the Sredni and Rybachi peninsulas are compared with similar data on the Upper Precambrian sequences of the Timan and Varanger Peninsula areas to reveal differences and similarities in the distribution of ages.  相似文献   

4.
The results of investigations of Upper Vendian?Lower Cambrian deposits in the northeastern part of the Baltic monocline specify views on the evolution of depositional environments of sedimentary successions constituting the basal part of the sedimentary cover in inner areas of the northwestern East European Platform. It is shown that the Late Vendian and initial Cambrian were characterized by the consecutive influx of relatively mature terrigenous detrital material that originated from both the weathering crust of the Baltic Shield and new sources. Its deposition was interrupted by notable, although likely asynchronous, hiatuses, which are registered at the base of the Upper Vendian Vasileostrovskaya and Voronkovo formations and Lower Cambrian Lomonosov Formation. In the Late Vendian, sedimentary material was transported from the Baltic Shield, while beginning from the initial Early Cambrian the additional contribution to the formation of the sedimentary cover of the Baltic monocline was provided by coarse-grained sedimentary material from the Timan margin of the Baltica as follows from U?Pb isotopic ages obtained for detrital zircons. At the same time, lithogeochemical parameters of fine-grained rocks experienced no substantial changes.  相似文献   

5.
温都尔庙群锆石的LA-MC-ICPMS U-Pb年龄及构造意义   总被引：11，自引：5，他引：6  
温都尔庙群分布在内蒙古中部地区,分下部桑达来呼都格组和上部哈尔哈达组,通常被认为属于蛇绿岩套组合,形成时代也一直存在争论。详细的野外调查表明,温都尔庙群不完全是蛇绿岩组合,还发育洋内弧的玄武岩-玄武安山岩-安山岩组合。所以,温都尔庙群为一套包含大洋洋壳、洋内弧等不同时代和成因的增生杂岩。对温都尔庙群洋内弧变质安山岩及变质碎屑岩进行锆石LA-MC-ICPMS法U-Pb同位素测年表明:桑达来呼都格组上部洋内弧变质安山岩年龄为470±2Ma。哈尔哈达组两个样品(10NM142、10NM143)的碎屑锆石年龄主要集中在445~480Ma范围内,其中10NM143样品中最年轻谐和年龄多在424~438Ma之间,表明至少有一部分地层形成于中志留世。考虑温都尔庙群蛇绿岩形成时代(497~477Ma)、高压变质时代(446±15Ma~453±1.8Ma)及晚志留世西别河组不整合覆盖其上的事实,桑达来呼都格组可能形成于寒武纪-晚奥陶世,哈尔哈达组形成于晚奥陶世-中志留世。因此,温都尔庙群是形成于寒武纪-中志留世的变质增生杂岩。  相似文献   

6.
青藏高原北部古近纪晚期大面积发育唢呐湖组湖相沉积,主要为砖红色、棕色、灰白色泥灰岩、泥岩、粉砂岩互层,夹石膏层和灰岩,广泛出露于羌塘中部、可可西里、东昆仑南部,形成时代为41.1±0.8~32.5!0.3Ma,向可可西里东部过渡为雅西错群。对双湖采坑唢呐湖组上部湖相沉积地层进行详细观测和系统取样,对泥灰岩和粘土岩样品选碎屑锆石作LA-MC-ICP-MS U-Pb同位素测年,对不同层位泥灰岩、粘土岩、灰岩样品作碳、氧同位素分析,结合区域地质相关资料,良好揭示了碎屑锆石来源、沉积地貌环境及古海拔高度。双湖采坑唢呐湖组碎屑锆石绝大部分为岩浆锆石,统计分析碎屑锆石U-Pb年龄,发现存在4期峰值,分别为280~200Ma、780~830Ma、1920~1790Ma、2600~2360Ma;对比区域地质和岩浆岩测年资料,推断晚二叠世—三叠纪(280~200Ma)碎屑锆石主要来自于羌中隆起岩浆岩,新元古代中期(~800Ma)、古元古代晚期(~1800Ma)、太古宙末期—古元古代初期(~2500Ma)碎屑锆石主要来自于东昆仑造山带。双湖采坑碎屑锆石部分测点U-Pb同位素呈线性分布,交点年龄及谐和年龄为1883!51~1837!12Ma、2483!24~2520!37Ma,对应东昆仑造山带早前寒武纪2期岩浆热事件年龄。根据唢呐湖组湖相沉积空间分布和碎屑锆石U-Pb年龄统计分布,推断青藏高原北部古近纪晚期发育自北向南流动的古水系,古洪流将东昆仑造山带出露地表的前寒武纪基底岩浆锆石自北向南长距离搬运,汇聚于双湖古湖盆并沉积于唢呐湖组。根据双湖采坑唢呐湖组湖相沉积碳同位素和氧同位素,估算双湖古湖盆35~34Ma古海拔高度为3427~3510m,这与应用Airy均衡模式根据地壳厚度和密度变化估算的古海拔高度在误差范围内基本吻合。  相似文献   

7.
As a result of studying the Vetreny Belt greenstone structure (the southeast of the Baltic Shield), zircons from terrigenous deposits of the Toksha Formation, underlying the section of the sedimentary-volcanogenic complex, and zircons of the Vetreny Belt Formation, deposits of which crown the section, were dated. The results of analysis of age data of detrital zircons from quartzites of the Toksha Formation indicate that Mesoarchean greenstone complexes and paleo-Archean granitogneisses of the Vodlozero Block (Karelia) were the provenance area from which these zircons were derived. The occurrence of the youngest zircons with age of 2654.3 ± 38.5 Ma is evidence that the formation of the Vetreny Belt, including the Toksha Formation, began no earlier than this time. Zircons from volcanic rocks of the Vetreny Belt yielded the age of 2405 ± 5 Ma. Thus, the age interval of the formation of the sedimentary-volcanogenic complex of the Vetreny Belt ranges from 2654.3 ± 38.5 to 2405 ± 5 Ma.  相似文献   

8.
Laser ablation ICP-MS U–Pb zircon geochronology of detrital zircons from a contact metamorphic sample of the Brixen Quartzphyllite from the innermost part of the contact aureole adjacent to the Brixen granodiorite yielded three different Precambrian concordia ages: zircon cores and an older generation of zircons give a maximum age of 2,023 ± 31 Ma, zircon rims and a younger generation of single grains yield a concordia age of 882 ± 19 Ma. A third generation of single zircon grains yields an age of 638 ± 20 Ma. In contrast to Austroalpine quartzphyllite complexes from the Eastern Alps neither Cambrian/Ordovician (570–450 Ma) nor Carboniferous (360–340 Ma) ages on single zircons have been observed so far in these samples. These ages provide evidence of a complex pre-Variscan evolution of the Southalpine basement since these data suggest a possible affinity of the Southalpine basement to Gondwana-related tectonic elements as well as to a possible Cadomian hinterland. This study shows that dating detrital zircons of the Brixen Quartzphyllites has great potential for providing age constraints on the complex geological evolution of the Southalpine basement.  相似文献   

9.
北秦岭宽坪岩群变质沉积岩年代学及地质意义   总被引：2，自引：1，他引：1       下载免费PDF全文
宽坪岩群位于北秦岭造山带,主要由广东坪岩组斜长角闪岩、四岔口岩组云母石英片岩及谢湾岩组的大理岩组成。通过LA-MC-ICPMS锆石U-Pb测年研究,宽坪岩群谢湾岩组碎屑锆石年龄为400~3502 Ma,其中最年轻一组的206Pb/238U年龄在380~418 Ma,结合黑云母40Ar/39Ar（370.9±2.0）Ma的变质年龄,表明谢湾岩组形成在晚泥盆世。四岔口岩组碎屑锆石年龄介于512~3598 Ma,最年轻的一组锆石206Pb/238U年龄在512~549 Ma,其黑云母40Ar/39Ar变质年龄为（370.4±1.8）Ma,表明该组形成于512 Ma（早寒武世）之后,晚泥盆世之前,主体很可能形成于早古生代。宽坪岩群是由不同时代的地层和岩片构成,应该进一步解体。宽坪岩群物源来自华北陆块、秦岭造山带和扬子陆块。其变形变质时代为晚泥盆世,代表了北秦岭造山带碰撞造山的结束时代。  相似文献   

10.
黑龙江西部龙江地区位于中亚造山带东段,黑河-贺根山缝合带与西拉木伦缝合带之间,地层记录了两大古板块之间古亚洲洋闭合过程的信息。本文对龙江地区乐平统林西组和下-中三叠统老龙头组的砂岩样品进行碎屑重矿物和碎屑锆石U-Pb同位素年代学研究。碎屑重矿物组合以锆石+磷灰石+金红石+角闪石+绿帘石+重晶石的组合为特征,表明物源主要来自于中酸性岩浆岩,并有少量变质岩及沉积岩组分。林西组样品最年轻的锆石年龄为278±3Ma,老龙头组样品最年轻的锆石年龄为247±3Ma、243±4Ma及237±3Ma,结合前人的研究,限定了林西组沉积于乐平世,老龙头组沉积于早三叠世-中三叠世。碎屑锆石年龄谱明显分为五组:237～258Ma、270～329Ma、357～558Ma、680～1633Ma及1893～1966Ma。其中237～258Ma的碎屑锆石主要来自与古亚洲洋洋壳消亡前的俯冲增生过程相关的火山活动,270～329Ma的碎屑锆石主要来自大石寨组火山岩及其同期侵入岩,357～558Ma的碎屑锆石来自早古生代-晚古生代早期岩浆弧,680～1633Ma的碎屑锆石可能来自兴安及额尔古纳地块的变质基底,而较古老的～1800Ma的锆石年龄暗示了华北克拉通基底的物源信息。通过研究发现林西组及老龙头组样品前30%年轻的碎屑锆石年龄与地层沉积年龄之差都小于100Ma,结合对砂岩碎屑组成、重矿物组合及盆地与火山弧位置关系的研究,认为研究区乐平世-中三叠世沉积盆地具有汇聚背景,为弧前盆地。  相似文献   

11.
藏东左贡-竹卡地区一些关键地层的时代和物源区示踪   总被引：1，自引：1，他引：0  
金鹭  王青  朱弟成  谢锦程  张亮亮 《岩石学报》2017,33(8):2523-2534
因地层时代和物源区缺乏有效约束,限制了对龙木错-双湖缝合带东向延伸的北澜沧江缝合带北段构造演化历史的认识。本文报道了位于北澜沧江缝合带北段藏东左贡-竹卡地区的酉西群、竹卡群和甲丕拉组的锆石U-Pb年龄数据,在酉西群变质砂岩和甲丕拉组砂岩中获得的最年轻碎屑锆石U-Pb年龄加权平均值分别为410±7Ma(n=3)和215±1Ma(n=2),将二者的最大沉积时代分别限定为早泥盆世和晚三叠世。竹卡群英安岩的锆石U-Pb年龄(240±1Ma)表明火山岩浆作用发生于中三叠世。碎屑锆石年龄频谱表明,酉西群兼具南羌塘地体约950Ma的碎屑锆石年龄指标和拉萨地体约1110Ma的年龄指标,表明其初始物源可能来自东冈瓦纳大陆内部印度大陆与南极洲之间的Eastern Ghats-Rayner和澳大利亚大陆和南极洲之间的Albany-Fraser-Bunger-Windmill造山带。甲丕拉组碎屑锆石最年轻的年龄峰值(225±2Ma;n=25)及其Hf同位素组成(-15.7~-4.2)与东达山岩基的相似性,指示甲丕拉组的物源很可能来自邻近的东达山岩基。甲丕拉组最年轻的碎屑锆石年龄(215Ma)与东达山岩基最年轻的花岗岩浆活动同期。这一结果,结合东达山地区甲丕拉组与下伏地层之间发生的与羌塘中央隆起带同期的区域性角度不整合事件,提出在北澜沧江北段的东达山地区,在东达山花岗岩基岩浆作用之后(约215Ma)甲丕拉组磨拉石沉积之前,很可能发生了快速隆升,与青藏高原羌塘中央隆起带的隆升剥露事件同期,可能受控于北澜沧江古特提斯洋壳板片的断离。  相似文献   

12.
This paper presents the results of a study of the Paleoproterozoic basal garnet-kyanite-staurolite-two-mica paraschists from the Kukasozero structure of the Karelides of Northern Karelia, Baltic Shield, underlying Neoarchean acid metavolcanic rocks, and schists with quartz, phengite, kyanite, staurolite, garnet, and tschermakite located in the Paleoproterozoic rocks and considered to be metasomatic in origin. It was established that the sedimentary protolith of the Paleoproterozoic paraschists contains detritus of Neoarchean igneous rocks as follows from detrital 2737 ± 11 Ma zircons with oscillatory magmatic zoning. Metavolcanic 2757 ± 13 Ma rocks, close in age and composition, are known directly in the framework of the Kukasozero structure and are considered to be the most likely source of the sedimentary schist protolith. The coincidence of the Nd-model ages of paraschists (t DM is 2.73–2.76 Ga) with the age of detrital zircons indicates no contribution of older rocks to the protolith composition. The age of magmatic crystallization of metavolcanic rocks directly underlying the Paleoproterozoic paraschists is 2681 ± 18 Ma and coincides with the age of porphyry granites in the western framework of the structure (2680.3 ± 3.6 Ma). No detrital zircons of similar age were found in basal paraschists, but the restricted amount of dated zircons does not allow us to draw a final conclusion about the absence of detritus of the underlying metavolcanic rocks in the paraschist protolith. It was confirmed that phengite-bearing schists are the products of acid metasomatism of the Paleoproterozoic amphibolites and amphibole schists (metavolcanic rocks). The metasomatic features were revealed in garnet-kyanite-staurolite-two-mica paraschists, so the strict identification of their sedimentary protolith is impossible. The paraschists do not represent metamorphosed weathering crust, because acid metasomatism gives a false impression of the greater maturity of the primary sedimentary rocks.  相似文献   

13.
The data on the age of sediments and their sources were first obtained by isotopic methods and lithological-petrographic observations for the Priozersk and Salmi formations in the northeastern Pasha-Ladoga basin. Wide development of coarse-grained terrigenous rocks and peculiar structures point to the proximity of provenances and dominant sedimentation in terrestrial settings. U-Pb dating of 168 detrital zircons revealed that approximately 87% of all grains are Early Riphean in age, while other grains are dated back to the Early Proterozoic. Archean age is documented for only two zircon grains. It is established that detrital material of sandstones from the Priozersk and Salmi formations largely originate from the Salmi Massif (1.55–1.53 Ga) and secondarily from the Svecofennian intrusions of the northern Ladoga region aged approximately 1.88 Ga, which is confirmed also by Sm-Nd data. The occurrence of detrital zircons dated at approximately 1480–1490 Ma indicates development of coeval magmatic bodies in the immediate proximity to the sedimentation basin, which remain undiscovered. The concordant age obtained for the youngest detrital zircon grain points to the onset of sedimentation in the basin after 1477 ± 8 Ma ago. Thus, Riphean sedimentation on the eastern slope of the trough commenced only 20 Ma prior to the emplacement of the Valaam Sill.  相似文献   

14.
阿尔泰造山带广泛分布各种变质沉积岩并发育典型递增变质带,变质沉积岩变质之前的沉积时代与物源特征对于限定成岩历史以及造山带演化具有重要意义。文章对采自阿勒泰组变质带中石英岩夹层样品进行了岩相学分析并采用LA-ICP-MS方法对其碎屑锆石进行了U-Pb年代学分析。共获得100个谐和或近于谐和的碎屑锆石年龄,表面年龄分布范围为(443±5)Ma至(2682±19)Ma。碎屑锆石年龄主要集中在寒武纪(486~540 Ma)并具有527~535 Ma的年龄峰值,可能源于区域内同时代的岩浆活动。新元古代年龄约占1/4,少量锆石具有古中元古代甚至太古宙年龄。结合年轻碎屑锆石年龄以及直接侵入该变质带中的英云闪长岩年龄可确定石英岩原岩的沉积时限为早志留世—早泥盆世,其后发生变质作用。古老碎屑锆石在该地区缺乏对应的岩石,可能源于区内隐伏的古老基底岩石或邻区古老陆块。  相似文献   

15.
During our study we obtained the first age datings of detrital zircons from metasandstones of the Ladoga Group (North Ladoga Region, Russia) with the U-Pb isotopic method using the SHRIMP-II ion microprobe. The data obtained made it possible to clarify the lower age limit of sedimentation and to obtain additional age data for evaluating the chemical composition and an age of source areas. This work presents the results of isotopic-geochemical (Sm-Nd) and geochemical studies of metasediments. High LREE concentrations, a high La/Sc ratio and a low Cr/h ratio, and the presence of a distinct Eu-minimum (Eu/Eu* = 0.54–0.72) indicate a significant role of acidic terrigenous material in source areas. In addition, the data of the isotope analysis of detrital zircons show that sediments of the Ladoga Group accumulated from the destruction of Proterozoic rocks (1.9–2.0 Ga; a proportion in sediments is 60–70%) and, to a lesser extent, Archean rocks (2.54–2.74 and 2.9–3.01 Ga; the proportion in sediments is 30–40%). One of the Archean source areas could be granite-gneisses of the Pitkyaranta-Koirinoya dome structure with the U-Pb zircon age of 2659 ± 15 Ma. We have established the lower age limit of sedimentation as 1.9 Ga within the measurement error. The Sm-Nd model ages obtained (2.5–2.6 Ga for sediments of the Ladoga Group and over 3.4 Ga for granite-gneisses of the dome structure) suggest a significant contribution of ancient crustal source area into source rocks. Our age data agree well with those for svecofennides of Finland.  相似文献   

16.
邱啸飞 《地质学报》2022,96(11):3784-3798
扬子克拉通前泥盆纪地壳演化过程一直是地学界研究的热点。本文报道了扬子克拉通北部武汉地区玉笋山剖面的志留系坟头组和泥盆系云台观组碎屑沉积岩中锆石U- Pb年龄和Hf同位素组成。结果表明，武汉地区坟头组和云台观组样品中最年轻的碎屑锆石年龄分别为430±5 Ma和415±5 Ma，将该地区坟头组和云台观组的沉积时代各限定在中志留世和晚泥盆世。碎屑锆石Hf同位素特点表明，沉积物源区在中太古代、新太古代以及新元古代形成了少量初生地壳，而古老地壳的再造主要发生在新太古代、新元古代和古生代，区域上最显著的初生地壳生长时期则是古元古代。综合对比扬子克拉通北部东、西两侧具有明显不同的锆石U- Pb年龄、微量元素和Hf同位素组成，暗示扬子克拉通可能由多个相对独立地壳演化过程的部分构成，而不具有统一的早前寒武纪基底。  相似文献   

17.
为厘清内蒙古林西县会长地一带出露的一套生物化石匮乏的砂砾岩组合的地质时代、地层归属及其碎屑物质来源，进而探讨西拉木伦河缝合带的形成演化，对研究区砂岩样品进行了碎屑锆石LA-ICP-MS U-Pb年代学研究。测试结果主要分布在6个年龄区间：（285±4）~（246±4） Ma （峰值为264 Ma）、（317±5）~（293±4） Ma （峰值为310 Ma）、（610±10）~（344±6） Ma （主峰值为423 Ma）、（992±14）~（907±13） Ma、（1 467±18）~（1 424±22） Ma、（1 948±14）~（1 768±16） Ma，另具3颗年龄分别为（1 171±17）、（1 238±17）和（2 443±31） Ma的锆石。锆石CL图像与Th/U值共同指示绝大多数锆石为岩浆结晶锆石。264 Ma的峰值年龄限定了地层的沉积下限为晚二叠世，应属林西组；沉积物源区示踪显示砂岩沉积时具佳蒙板块（北方地块群）与华北板块两个物源区，指示佳蒙板块（北方地块群）与华北板块于晚二叠世时已拼合，拼合位置为西拉木伦河一线。  相似文献   

18.
刘凯  王任  石万忠  张威  覃硕  齐荣  徐立涛 《地球科学》2021,46(2):540-554
鄂尔多斯盆地北部上古生界砂岩碎屑组分、岩屑类型和重矿物组合具有明显的东西分带性,但是其物源来源及差异性尚不明确.利用锆石LA-ICP-MS U-Pb定年方法,对鄂尔多斯盆地北部杭锦旗地区下石盒子组碎屑锆石年龄分布及变化特征进行了研究,明确了不同年龄组分碎屑锆石的来源,并分析了不同物源体系及差异性.结果表明:不同地区下石盒子组碎屑矿物含量存在明显差异,由西向东岩屑含量逐渐增加,石英含量逐渐减小;下石盒子组锆石年龄主要呈现280~340 Ma、400~450 Ma、1 700~2 000 Ma和2 200~2 500 Ma 4个峰值区间段,从东部地区到西部地区,锆石显生宙年龄组分所占比例逐渐增加,且中部、西部地区新出现400~450 Ma的年龄段;对比周源岩体同位素年龄,西部地区物源主要来自于阿拉善地块,东部和中部地区物源主要来自于大青山-乌拉山、阴山和集宁地区,同时中部地区还受到阿拉善地块物源输入的影响;结合下石盒子组砂岩锆石定年结果和碎屑矿物含量、岩屑类型分布特征,认为杭锦旗地区发育多物源体系,并据此将研究区分为西部物源区、中部混合物源区及东北部物源区.   相似文献   

19.
LA-ICP-MS U-Pb dating and in situ Hf isotope analysis were carried out for the detrital zircons to constrain the depositional age and provenance of the Wawukuang Formation, which is believed as the earliest unit of the Laiyang Group in the Jiaolai Basin, and its implications. Most of these detrital zircons from the feldspar quartz sandstone in the Wawukuang Formation are magmatic in origin, which are euhedral-subhedral and display oscillatory zoning in CL images; whereas few Late Triassic detrital zircons are metamorphic in origin and structureless in CL images. U-Pb isotopic dating of 82 zircon grains yields age populations at ca. 129 Ma, 158 Ma, 224 Ma, 253 Ma, 461 Ma, 724 Ma, 1851 Ma and 2456 Ma. U-Pb dating and Hf isotopic results indicate that: 1) the Wawukuang Formation deposited during the Early Cretaceous (129-106 Ma); 2) the detrital zircons with the ages of 1851 Ma and 2456 Ma mainly sourced from the Precambrian basement rocks of the North China Craton; the Neoproterozoic (729-721 Ma) magmatic zircons and the Late Triassic (226-216 Ma) metamorphic zircons sourced from the Su-Lu terrane; The Late Paleozoic detrital zircons could source from the Late Paleozoic igneous rocks in the northern margin of the North China Craton; the Late Triassic (231-223 Ma) magmatic zircons and the 158-129 Ma zircons sourced from the coeval igneous rocks in the Jiaobei and Jiaodong; 3) the deposition age and provenance of the Jiaolai Basin are different from those of the Hefei Basin; 4) the recognition of clastic sediments from the Su-Lu terrane in the Wawukuang Formation suggests that the Su-Lu terrane was under denudation in the Early Cretaceous. ©, 2015, Science Press. All right reserved.  相似文献   

20.
本文对东天山黄山-镜儿泉岩浆铜镍硫化物成矿带原来古生物地层学方法厘定的早石炭统干墩组和晚石炭统梧桐窝子组的碎屑锆石进行了激光等离子质谱(LA-ICP-MS)U-Pb年代学研究。干墩组碳质板岩、变质砂岩和变质长石石英砂岩中的碎屑锆石U-Pb年龄分别为301~491 Ma、307~426 Ma和313~461 Ma,最年轻锆石的加权平均值分别为307.1±3.7 Ma、310.4±2.2 Ma、315.0±10 Ma,表明干墩组最大沉积年龄为晚石炭世。而梧桐窝子组变质砂岩和变质凝灰岩的碎屑锆石年龄为384~448 Ma和393~448 Ma,最年轻锆石的加权平均值分别为386.5±5.8 Ma、394.6±4.5 Ma,确定其最大的沉积年龄为早—中泥盆世。这与近年来对侵位于这些地层的火成岩体的锆石U-Pb年龄一致,说明康古尔-雅满苏岛弧带至少从中泥盆世就开始发育。中—下泥盆统梧桐窝子组与上石炭统干墩组地层之间上泥盆统—下石炭统地层厚度约为10 km,说明侵位于这两套地层中的含铜镍硫化物镁铁-超镁铁岩体分别代表了岩浆通道系统的深部岩浆通道相和浅部岩浆房,整个岩浆通道系统的纵向规模大约为10 km。  相似文献   

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