The Earliest History of the Skaergaard Magma Chamber: a Textural and Geochemical Study of the Cambridge Drill Core
The Earliest History of the Skaergaard Magma Chamber: a Textural and Geochemical Study of the Cambridge Drill Core
复制标题
斯卡尔加德岩浆室的最早历史：剑桥钻芯的结构和地球化学研究
DOI：
10.1093/petrology/egv034
复制
发表时间：
2015
影响因子：
3.9
通讯作者：
Holness M
中科院分区：
文献类型：
--
作者：
Holness M
剑桥钻芯提供了 Skaergaard 侵入岩底部堆积物的连续样本，包括来自未暴露隐藏区的 ∼150 m 地层。块体岩石地球化学以及橄榄石矿物成分和钻芯的辉石-斜长石-斜长石二面角被解释为斯卡尔加德岩浆室早期历史的记录。对辉石模式和形态的详细地球化学和微观结构研究表明，没有明确的标记可用于精确定位钻芯采样的地层学中积云辉石的首次出现。斯卡尔加德岩浆房的早期历史涉及多批小批量岩浆的到来，每批岩浆都含有不同数量的橄榄石和斜长石斑晶。 –120 和 –108·8 m 之间的核心区域记录了至少三次独立但间隔很近的新岩浆涌入，在 –85 和 –65 m 处添加了更多岩浆。最后一次涌入的岩浆是由层状系列最低暴露地平线下方的累积物记录的，其中涉及大量岩浆，使岩浆室膨胀至最终尺寸。因此，斯卡尔加德岩浆室是由前寒武纪片麻岩和上覆高原熔岩之间的不连续处侵入的岩床逐渐膨胀形成的。因此，“斯卡尔加德母岩浆”应被视为充满房间的各种岩浆流入的综合和混合成分。
The Cambridge Drill Core provides a continuous sample of the lower part of the floor cumulates of the Skaergaard Intrusion, including ∼150 m of stratigraphy from the unexposed Hidden Zone. Bulk-rock geochemistry together with olivine mineral compositions and augite–plagioclase–plagioclase dihedral angles from the drill core are interpreted as a record of the early history of the Skaergaard magma chamber. A detailed geochemical and microstructural study of the mode and morphology of augite reveals no unambiguous markers that can be used to pinpoint the first appearance of cumulus augite in the stratigraphy sampled by the drill core. The early history of the Skaergaard magma chamber involved the arrival of multiple small batches of magma, each with a variable load of olivine and plagioclase phenocrysts. The region of the core between –120 and –108·8 m records at least three separate, but closely spaced, influxes of new magma, with more magma added at –85 and –65 m. The last influx of magma is recorded by the cumulates just below the lowest exposed horizons of the Layered Series, involving a large volume of magma that inflated the chamber to its final size. The Skaergaard magma chamber therefore formed by the progressive inflation of what was likely to have originated as a sill intruded at the discontinuity between the Precambrian gneisses and the overlying plateau lavas. The ‘Skaergaard parental magma’ should therefore be viewed as the integrated and mixed composition of the various magma influxes that filled the chamber.