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首页> 外文期刊>Contributions to Mineralogy and Petrology >The geochemical effects of olivine slurry replenishment and dolostone assimilation in the plumbing system of the Franklin Large Igneous Province, Victoria Island, Arctic Canada
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The geochemical effects of olivine slurry replenishment and dolostone assimilation in the plumbing system of the Franklin Large Igneous Province, Victoria Island, Arctic Canada

机译：加拿大北极岛富兰克林大火成岩省管道系统中的橄榄石泥浆补充和白云岩同化的地球化学效应

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摘要

The Neoproterozoic (similar to 723-716 Ma) Franklin Large Igneous Province exposed on Victoria Island in the Canadian Arctic is comprised of a sill-dominated magma plumbing system overlain by the coeval Natkusiak flood basalts. We have investigated three sections, separated by a total of >50 km of distance, of a sill (the Fort Collinson Sill Complex) emplaced just above a prominent sedimentary marker unit. The sill is characterized by a basal olivine-enriched layer (OZ: up to 55 % olivine) and an upper gabbroic unit. The observed diversity of olivine compositions in the OZ implies that bulk-rock MgO versus FeO arrays reflect accumulation of a heterogeneous olivine crystal cargo. We suggest that the OZ was formed as a late olivine slurry replenishment in a partially crystallized gabbroic sill, propagating for over 50 km along strike. This interpretation is consistent with Pb-isotope data, which show that at least three geochemically distinct magmas were emplaced into the Fort Collinson Sill Complex. The OZs exhibit a gradual westward evolution toward more Fe-rich bulk compositions. This is best explained by progressive mixing of the replenishing olivine slurry with a resident gabbroic mush during westward flow. Pb-isotopic signatures suggest that magmas near the inferred conduit feeder assimilated small amounts (<10 %) of dolostone country rock, which may have locally buffered olivine compositions to high-Fo contents.
机译：暴露于加拿大北极圈维多利亚岛上的新元古代（类似于723-716 Ma）富兰克林大火成岩省由一个以基岩为主导的岩浆管道系统组成，该系统被同时代的纳特库西亚克（Natkusiak）洪水玄武岩覆盖。我们已经研究了三个突出部分，该突出部分正好位于突出的沉积标记物单元正上方，相隔总距离> 50 km。窗台的特征是基底橄榄石富集层（OZ：高达55％的橄榄石）和上部辉长岩单元。在OZ中观察到的橄榄石成分的多样性暗示，块状岩石MgO与FeO阵列反映了异质橄榄石晶体货物的堆积。我们建议OZ是在部分结晶的辉长岩基岩中作为晚期橄榄石泥浆补给而形成的，沿罢工传播了50多公里。这种解释与铅同位素数据一致，该数据表明至少三个地球化学上不同的岩浆被放入了柯林森堡基尔复合体中。 OZ向着更多的富铁块状成分显示出逐渐向西的演化。最好的解释是，在向西流动时，补给的橄榄石浆液与常驻辉长岩糊不断混合。铅同位素特征表明推测的导管馈线附近的岩浆吸收了少量（<10％）的白云岩乡村岩石，这些岩石可能具有局部缓冲的橄榄石成分以达到高Fo含量。

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