The Baltoscandian margin detrital zircon signatures of the central Scandes
The Baltoscandian margin detrital zircon signatures of the central Scandes
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斯坎德斯中部的巴尔托斯坎德边缘碎屑锆石特征
DOI：
10.1144/sp390.20
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发表时间：
2013
影响因子：
2.7
通讯作者：
T. Thomsen
中科院分区：
文献类型：
--
作者：
D. Gee;A. Ladenberger;P. Dahlqvist;J. Majka;Y. Be'eri‐Shlevin;D. Frei;T. Thomsen
在斯堪的纳维亚加里东构造的中部，碎屑锆石特征提供了巴尔托斯坎迪亚结晶基底特征变化的证据，从前陆Autochthon的trans - Scandinavian火成岩带（TIB，约1650-1850 Ma）的典型晚古元古代花岗岩到腹地斯堪的纳维亚西南部Sveconorwegian造山带的典型中元古代-年龄剖面（约950-1700 Ma）。晚埃迪卡拉世至早寒武世Jämtlandian推覆体（下异石器统）的浅海Vemdal石英岩具有较强的双峰特征，TIB （1700-1800 Ma）和Sveconorwegian （900-1150 Ma）年龄占主导地位。瑞典下异特统中奥陶世（norr<s:1>组）浊浊岩来自西部，具有以seconorwegs时代为主的单峰特征，峰值为1000 ~ 1100 Ma，但有较老的中元古代锆石（1200 ~ 1650 Ma）的次级成分。最新的奥陶系浅海相石英岩也具有双峰特征，但比Vemdal石英岩更为分散。在中异古统绿片岩相下部，复大（Offerdal推覆体）和Särv推覆体的特征为单峰或双峰（950 ~ 1100 Ma和/或1700 ~ 1850 Ma），以年轻组或较老组为主导，其他中元古代组分则处于从属地位。在西弗推覆岩体下部的角闪岩—榴辉岩相上覆层中，变质沉积层以长石石英岩、富钙硅酸盐沙砾岩和大理岩为主，大部分单元具有与Särv推覆体相似的双峰特征，但较分散；一个具有与Jämtlandian推覆体的奥陶系浊积岩非常相似的单峰特征。在上异石器统，下Köli（波罗的海-近端，Virisen地系），晚奥陶世石英岩具有以seconorwegian时代（senu stricto）为主的单峰特征。在更北的斯坎德斯，先前发表的下异石东石英岩的锆石特征与Jämtland的Vemdal石英岩相似。北纬70°的卡拉克推覆体的数据对挪威巴尔托斯坎迪亚边缘来说并不陌生。它们确实显示出了来自罗马尼亚的影响（约560-610 Ma），这可以从推覆体的古重建中推断出来。因此，这里报道的和其他地方发表的碎屑锆石特征提供了支持证据，证明新元古代，从南部的类型地区，沿着波罗的海的波罗的斯坎迪亚边缘，向北延伸至北极高地。补充资料：LA-ICP-MS U-Pb分析可在http://www.geolsoc.org.uk/SUP18699上获得。
Abstract In central parts of the Scandinavian Caledonides, detrital zircon signatures provide evidence of the change in character of the Baltoscandian crystalline basement, from the characteristic Late Palaeoproterozoic granites of the Transscandinavian Igneous Belt (TIB, c. 1650–1850 Ma) in the foreland Autochthon to the typical, mainly Mesoproterozoic-age profile (c. 950–1700 Ma) of the Sveconorwegian Orogen of southwestern Scandinavia in the hinterland. Late Ediacaran to Early Cambrian shallow-marine Vemdal quartzites of the Jämtlandian Nappes (Lower Allochthon) provide strong bimodal signatures with TIB (1700–1800 Ma) and Sveconorwegian, sensu stricto (900–1150 Ma) ages dominant. Mid-Ordovician turbidites (Norråker Formation) of the Lower Allochthon in Sweden, sourced from the west, have unimodal signatures dominated by Sveconorwegian ages with peaks at 1000–1100 Ma, but with subordinate components of older Mesoproterozoic zircons (1200–1650 Ma). Latest Ordovician shallow-marine quartzites also yield bimodal signatures, but are more dispersed than in the Vemdal quartzites. In the greenschist facies lower parts of the Middle Allochthon, the Fuda (Offerdal Nappe) and Särv Nappe signatures are either unimodal or bimodal (950–1100 and/or 1700–1850 Ma), with variable dominance of the younger or older group, and subordinate other Mesoproterozoic components. In the overlying, amphibolite to eclogite facies lower part of the Seve Nappe Complex, where the metasediments are dominated by feldspathic quartzites, calcsilicate-rich psammites and marbles, most units have bimodal signatures similar to the Särv Nappes, but more dispersed; one has a unimodal signature very similar to the Ordovician turbidites of the Jämtlandian Nappes. In the overlying Upper Allochthon, Lower Köli (Baltica-proximal, Virisen Terrane), Late Ordovician quartzites provide unimodal signatures dominated by Sveconorwegian ages (sensu stricto). Further north in the Scandes, previously published zircon signatures in quartzites of the Lower Allochthon are similar to the Vemdal quartzites in Jämtland. Data from the Kalak Nappes at 70°N are in no way exotic to the Sveconorwegian Baltoscandian margin. They do show a Timanian influence (ages of c. 560–610 Ma), as would be expected from the palinspastic reconstructions of the nappes. Thus the detrital zircon signatures reported here and published elsewhere provide supporting evidence for a continuation northwards of the Sveconorwegian Orogen in the Neoproterozoic, from type areas in the south, along the Baltoscandian margin of Baltica into the high Arctic. Supplementary material: LA-ICP-MS U–Pb analyses are available at http://www.geolsoc.org.uk/SUP18699.