Crustal fluid contamination in the Bushveld Complex, South Africa: An analogue for subduction zone fluid migration
Crustal fluid contamination in the Bushveld Complex, South Africa: An analogue for subduction zone fluid migration
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南非布什维尔德杂岩中的地壳流体污染：俯冲带流体迁移的类比
DOI：
10.1080/00206814.2020.1795734
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发表时间：
2020
影响因子：
2.6
通讯作者：
Boudreau, Alan E.
中科院分区：
文献类型：
--
作者：
Benson, Erin;Connolly, James A.;Boudreau, Alan E.
2.06 Ga Bushveld 岩浆的结晶形成了 9 公里（最大）的超镁铁质和镁铁质岩石序列，当它对德兰士瓦序列中先前未改变的下伏沉积岩的 3 多公里部分进行热变质时，产生了大量的乡村流体 - 其几何形状类似于俯冲岩石圈板片被上覆地幔岩石加热时所看到的形状。布什维尔德杂岩体中靠近基底岩石的底辟上升流处存在角砾岩管和其他大型管状特征，这表明下盘沉积物脱水过程中产生的超压流体被底辟结构集中，使得乡村流体迅速渗透布什维尔德岩石。对现有稳定和放射性同位素证据的重新检查与主区岩浆受到 1-2% 乡村流体污染的情况一致。下盘脱水的数值模型同样表明，大部分乡村流体在渗入布什维尔德岩床时将被限制在管状通道中。模型还表明，变质光环的最大程度大约在主区开始结晶的同时达到。有人认为，布什维尔德岩床的快速膨胀导致超压乡村流体突然发生灾难性的喷出，从而产生直接物质并污染主区岩浆，导致主区地壳稳定和放射性同位素特征（Sr、Nd、O 等）富集。通过类比，还表明地幔楔中的水化熔融是由类似的板片流体突然流入所驱动的，这些板片流体能够通过快速通道流入来保留其地球化学和同位素特征。这可以通过在上板片-地幔接触处的底辟结构处聚焦流动来辅助。
Crystallization of the 2.06 Ga Bushveld magma formed a 9 km (maximum) sequence of ultramafic and mafic rocks that generated a large volume of country fluid as it thermally metamorphosed a 3+ km section of previously unaltered underlying sedimentary rocks of the Transvaal sequence – a geometry similar to that seen as subducting lithospheric slabs are heated by overlying mantle rocks. The presence of a diatreme (breccia pipe) and other large, pipe-like features in the Bushveld Complex located proximal to diapiric upwelling of the basement rocks suggest that overpressured fluids generated during dehydration of the footwall sediments are focused by the diapiric structures such that the country fluids rapidly penetrate the Bushveld rock. A re-examination of existing stable and radiogenic isotopic evidence is consistent with contamination of Main Zone magmas by 1–2% country fluid. Numeric modelling of the footwall dehydration similarly shows that most of the country fluids will be confined to pipe-like channels as it percolates into the Bushveld sill. Modelling also suggests that the maximum extent of the metamorphic aureole was reached at about the same time that the Main Zone began to crystallize. It is proposed that rapid inflation of the Bushveld sill induced the sudden and catastrophic expulsion of overpressured country fluids to both generate the diatreme and contaminate the Main Zone magma, resulting in the Main Zone enrichment in crustal stable and radiogenic isotopic signatures (Sr, Nd, O and others). By analogy, it is also suggested that hydration melting in the mantle wedge is episodically driven by similar sudden influxes of slab fluids that are able to retain their geochemical and isotopic character by rapid channelled influx. This can be aided by flow focusing at diapirs structures at the upper slab-mantle contact.
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影响因子：
3.5
作者：
BARNES, SJ
通讯作者：
BARNES, SJ
南部非洲布什维尔德杂岩体内的铅同位素变化：一项勘察研究
影响因子：
2.3
作者：
R. Harmer;J. Auret;B. Eglington
通讯作者：
B. Eglington
影响因子：
2.9
作者：
C. M. Schiffries;B. Skinner
通讯作者：
B. Skinner
关于南非布什维尔德杂岩 Makhutso 花岗岩的年龄和遗传关系的注释
DOI：
10.1016/0168-9622(88)90033-4
发表时间：
1988
期刊：
Chemical Geology: Isotope Geoscience Section
影响因子：
--
作者：
F. Walraven
通讯作者：
F. Walraven
Bushveld 复合体热光环中的熔体生成和流体流动
影响因子：
3.9
作者：
N. Harris;Andy McMillan;M. Holness;R. Uken;M. Watkeys;N. Rogers;A. Fallick
通讯作者：
A. Fallick