Neoproterozoic magmatism and Carboniferous high-grade metamorphism in the Sredna Gora Zone, Bulgaria: An extension of the Gondwana-derived Avalonian-Cadomian belt?
Neoproterozoic magmatism and Carboniferous high-grade metamorphism in the Sredna Gora Zone, Bulgaria: An extension of the Gondwana-derived Avalonian-Cadomian belt?
复制标题
保加利亚斯雷德纳戈拉带的新元古代岩浆作用和石炭纪高级变质作用：冈瓦纳大陆衍生的阿瓦隆阶-卡多米亚带的延伸？
DOI：
10.1016/j.precamres.2006.01.026
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发表时间：
2006
影响因子：
3.8
通讯作者：
K. Kolcheva
中科院分区：
文献类型：
--
作者：
Charles W. Carrigan;S. Mukasa;I. Haydoutov;K. Kolcheva
阿尔卑斯-喀尔巴阡造山带内大量的基底构造记录了欧洲南缘新元古代至古生代的发育过程。这一区域对于充分了解北方（即，Laurentia和Baltica）和南部（即，在这段时间里，冈瓦纳）大陆，但它鲜为人知。我们从保加利亚中部Sredna戈拉区的基底岩石样品中用高分辨二次离子质谱法测定了锆石年龄，以阐明该地区前阿尔卑斯构造的发展。正片麻岩中岩浆环带锆石的年龄分别为616.9± 9.5Ma和595± 23 Ma，表明它们是新元古代侵位的。这些年龄与形成横跨北美和欧洲的冈瓦纳大陆衍生岩石基底的新元古代岩石非常相似。Sredna戈拉带位于其他冈瓦纳衍生岩带外侧的位置，以及新元古代晚期的火成岩侵位年龄，使我们认为Sredna戈拉带代表了冈瓦纳衍生岩带的延续，这些冈瓦纳衍生岩带目前位于沿着劳伦蒂亚东端和波罗的海西南缘。混合岩副片麻岩中的浅色体中的锆石含有普遍存在的、高铀的、均匀的变质边缘，其年龄为336.5±5.4Ma。这个变质作用的年龄与其他已发表的中欧和西欧华力西变质作用的年龄是无法区分的。在无色体的锆石颗粒的核心有变化的内部分带模式，并解释为原始碎屑物质在母岩沉积岩。对这些碎屑岩芯的HR-SIMS测年得出了几个年龄群体，分别为500-700、900-1100、1900-2200、2350、2550和2700 Ma。作为混合岩副片麻岩母岩的沉积岩的沉积时代被限定在奥陶纪（最年轻的碎屑年龄为~ 500 Ma）和早石炭世（高级变质年龄为336.5±5.4Ma）之间。总的来说，这些数据表明，冈瓦纳派生的火山岩和华力西造山运动在南欧向东延伸得比以前认识到的要远得多。
Numerous basement massifs within the Alpine-Carpathian Orogen record the Neoproterozoic to Paleozoic development of the southern margin of Europe. This area is critical for adequate understanding of the interactions between the northern (i.e., Laurentia and Baltica) and southern (i.e., Gondwana) continents during this time, yet it is poorly known. We dated zircon by HR-SIMS from samples of basement rocks of the Sredna Gora Zone in central Bulgaria in order to shed light on the pre-Alpine tectonic development of this region. Analyses of magmatically zoned zircons from orthogneiss samples yield ages of 616.9±9.5 and 595±23Ma, indicating Neoproterozoic emplacement ages for these units. These ages are very similar to the Neoproterozoic rocks that form the basement of Gondwana-derived terranes across North America and Europe. The position of the Sredna Gora Zone outboard of other Gondwana-derived terranes, along with the Late Neoproterozoic igneous emplacement age, lead us to suggest that the Sredna Gora Zone represents a continuation of the Gondwana-derived terranes that are presently positioned along the eastern end of Laurentia and the southwestern margin of Baltica. Zircons from a leucosome enclosed in migmatitic paragneisses contain ubiquitous, high-U, homogeneous metamorphic rims that yield an age of 336.5±5.4Ma. This age of metamorphism is indistinguishable from other published ages of Variscan metamorphism across Central and Western Europe. Cores of zircon grains in the leucosome have variable interior zoning patterns, and are interpreted as original detrital material in the parent sedimentary rock. HR-SIMS dating of these detrital cores yields several age populations at ∼500–700, 900–1100, 1900–2200, 2350, 2550, and 2700Ma. The depositional age of the sedimentary rocks that were the parent to the migmatitic paragneisses is constrained between the Ordovician (youngest detrital age ∼500Ma) and the Early Carboniferous (high-grade metamorphism at 336.5±5.4Ma). Collectively, these data suggest that both Gondwana-derived terranes and the Variscan Orogeny extend much farther eastward in southern Europe than has been previously recognized.