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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Ordovician palaeogeography with new palaeomagnetic data from the Montagne Noire (Southern France)
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Ordovician palaeogeography with new palaeomagnetic data from the Montagne Noire (Southern France)

机译：奥陶纪古地理与来自Montagne Noire（法国南部）的新古地磁数据

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摘要

A joint palaeomagnetic and ~(40)Ar/~(39)Ar study has been performed on two olistolithic blocks from the Cabrieres Wildflysch in the Montagne Noire region of the Massif Central in France. There, andesitic volcanic and volcaniclastic rocks of Llanvirn-Early Caradoc age (ca 470-458 Ma) occur. Despite extensive secondary alteration, destruction of the dominant magnetic mineral phase and ~(40)Ar/~(39)Ar whole rock experiments that demonstrate that the volcanic rocks suffered significant argon loss, a positive fold test and the presence of dual polarities suggest that a primary, Ordovician magnetisation has mostly survived. This is one of the few documented cases where the argon system was substantially resent whilst a subordinate set of small, relatively unaltered magnetite grains, probably hosted in silicates, still carry the original, in this case Ordovician, remanence. The new data show that the Montagne Noire region was located at high southerly latitudes (68°~(+17)/_(-15)) during the Mid-Ordovician. This latitude represents the location for NW Gondwana of which the Massif Central was a part. Palaeomagnetic data from all the Central European massifs and terranes demonstrate a close link to the Gondwana Margin during the Lower and Middle Ordovician.
机译：对法国Massif Central的Montagne Noire地区Cabrieres Wildflysch的两个微石块进行了古地磁和〜（40）Ar /〜（39）Ar联合研究。在那里发生了兰维恩-早期卡拉多克时代（大约470-458 Ma）的安第斯火山岩和火山碎屑岩。尽管发生了广泛的次生蚀变，但主要磁性矿物相的破坏和〜（40）Ar /〜（39）Ar整体岩石实验表明，火山岩遭受了严重的氩气损失，正折叠测试以及双极性的存在表明一次奥陶纪的磁化强度大都幸存了下来。这是少数文献记载的案例，其中氩气系统受到强烈反感，而次要的一组较小的，相对未变的磁铁矿颗粒（可能包含在硅酸盐中）仍然具有原始的剩磁，在这种情况下为奥陶纪。新数据表明，蒙塔涅诺瓦黑地区在中奥陶纪时期位于南纬高纬度地区（68°〜（+17）/ _（-15））。纬度代表了Massif Central所在的NW Gondwana的位置。来自中欧所有地块和地层的古地磁数据表明，在下奥陶纪和中奥陶纪时期与冈瓦纳边缘有着密切的联系。

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