The Petrology of Mullite-bearing Peraluminous Xenoliths: Implications for Contamination Processes in Basaltic Magmas
The Petrology of Mullite-bearing Peraluminous Xenoliths: Implications for Contamination Processes in Basaltic Magmas
复制标题
含莫来石过铝包体的岩石学：对玄武岩浆污染过程的影响
DOI：
10.1093/petroj/40.4.549
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发表时间：
1999
影响因子：
3.9
通讯作者：
G. Rogers
中科院分区：
文献类型：
--
作者：
R. J. Preston;T. Dempster;B. Bell;G. Rogers
苏格兰马尔岛马尔岛斯克里登洛赫周围的古近纪熔岩区和下伏的莫因超群基底岩石中，侵入了一套从玄武岩到流纹岩的高级倾斜岩席。许多岩片是高度捕虏体，包含多种来自Moine变质沉积岩的地壳捕虏体类型，沿着有各种辉长岩堆晶捕虏体。最常见的捕虏体类型是几乎纯的石英岩和各种含莫来石的铝尖晶石，后者中的许多具有厚的斜长石、尖晶石和铝尖晶石的结晶边缘。斜长石是高度钙质（高达An 87），和邻近的主机玄武岩是常见的振荡带，这意味着从熔体结晶。斜长石晶体之间被困的口袋淬火，污染的基本熔体，其中包含骨骼斜长石和单斜辉石，并保存的证据之间的主机玄武岩和铝质地壳熔体的局部混合。蓝闪石核[如（87 Sr/86 Sr）55= 0.7074-0.7115]、斜长石边缘[如（87 Sr/86 Sr）55= 0.7137-0.7148]和相关的捕获熔体[如（87 Sr/86 Sr）55= 0.7126-0.7128]的Sr和Nd同位素值暗示了一系列复杂的岩浆-捕虏体相互作用。这些边缘的结构特征，矿物化学和同位素地球化学表明，它们已经从混合液体结晶形成的复杂的相互作用的铝质液体与基性岩浆。这种相互作用是通过液-液扩散、熔体的物理混合以及橄榄岩结晶产物与玄武质液体之间的各种反应进行的。这些地壳捕虏体保留了一套玄武岩片内的矿物熔体反应的详细记录，主要是由花岗岩熔体的生产和“散装”熔融的富铝云母岩性。
A suite of high-level inclined sheets ranging in composition from basalt through to rhyolite is intruded into the Palaeogene lava field and underlying Moine Supergroup basement rocks around Loch Scridain, Isle of Mull, Scotland. Many of the sheets are highly xenolithic, containing a wide variety of crustal xenolith types derived from the Moine metasedimentary rocks, along with various gabbroic cumulate xenoliths. The most common xenolith types are almost pure quartzites and a variety of mullite-bearing aluminous buchites, many of the latter having thick crystalline selvages of plagioclase, corundum and aluminous spinel. The plagioclase is highly calcic (up to An87), and adjacent to the host basalt is commonly oscillatory zoned, implying crystallization from a melt. Trapped between plagioclase crystals are pockets of quenched, contaminated basic melt, which contain skeletal plagioclase and clinopyroxene, and preserve evidence of local mixing between the host basalt and the aluminous crustal melts. Sr and Nd isotope values of the buchite cores [e.g. (87Sr/86Sr)55= 0.7074–0.7115], plagioclase selvages [e.g. (87Sr/86Sr)55= 0.7137–0.7148], and associated trapped melts [e.g. (87Sr/86Sr)55= 0.7126–0.7128], imply a complex series of magma–xenolith interactions. The textural characteristics, mineral chemistry and isotope geochemistry of these rims suggest that they have crystallized from a hybrid liquid formed by the complex interaction of the aluminous liquids with basic magmas. Such interaction proceeded via liquid–liquid diffusion, physical mixing of melts and a variety of reactions between the crystallization products of the buchites and the basaltic liquids. These crustal xenoliths preserve a detailed record of mineral–melt reactions within a suite of basaltic sheets, dominated by both the production of granitic melts and the ‘bulk’ melting of Al-rich micaceous lithologies.