The Platreef of the Bushveld Complex is one of three key stratigraphic units, along with the Merensky and UG-2 reefs, in which platinum-group elements are concentrated. The correlation between the Platreef and the stratigraphy from the western and eastern limbs of the BC has been challenging due to the heterogeneous and variable nature of the Platreef along strike. However, the discovery of the Flatreef, interpreted as the down dip, sub-horizontal extension of the Platreef, on the farms Turfspruit and Macalacaskop, opened new avenues for enquiry that allow the study of a magmatic stratigraphy less affected by footwall interaction. In this study, we report on the Sr isotope composition of plagioclase through an ~ 280-m-thick intersection of the Flatreef and its footwalls and hanging walls as intersected by borehole UMT-393 drilled on the farm Macalacaskop. Comparison of the Sr-isotopic composition and the anorthite content of plagioclase across this intersection with data from the Merensky and Bastard cyclic units elsewhere in the Bushveld Complex supports the contention that the Flatreef is a correlative of the Upper Critical Zone–Main Zone transition, including the Merensky and Bastard cyclic units. The available data suggest that the sulfides of the Flatreef and its correlatives in the remainder of the Bushveld Complex originally formed in a deeper staging chamber. During continued magma ascent some of the sulfides were entrained and deposited in the Flatreef.

中文翻译：

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Macalacaskop、北肢、Bushveld 复合体上 Flatreef 中锶同位素的变化：对 Merensky Reef 中铂族元素来源的影响

Bushveld Complex 的 Platreef 是三个关键地层单元之一，以及 Merensky 和 ​​UG-2 珊瑚礁，其中铂族元素集中。由于 Platreef 沿走向的异质性和可变性，Platreef 与 BC 西部和东部地层之间的相关性一直具有挑战性。然而，Flatreef 的发现被解释为 Platreef 的下倾、亚水平延伸，位于农场 Turfspruit 和 Macalacaskop，开辟了新的研究途径，允许研究受下盘相互作用影响较小的岩浆地层。在这项研究中，我们通过在 Macalacaskop 农场钻出的钻孔 UMT-393 与 Flatreef 及其下盘和挂墙相交的约 280 米厚的交叉点报告斜长石的 Sr 同位素组成。将穿过该交叉点的斜长石的 Sr 同位素组成和钙长石含量与布什维尔德杂岩体中其他地方的梅伦斯基和巴斯塔德循环单元的数据进行比较，支持这样的论点：Flatreef 是上临界带 - 主带过渡的相关物，包括Merensky 和 ​​Bastard 循环单元。现有数据表明，Flatreef 及其相关物在布什维尔德复合体其余部分的硫化物最初形成于更深的分期室。在持续的岩浆上升过程中，一些硫化物被夹带并沉积在 Flatreef 中。将穿过该交叉点的斜长石的 Sr 同位素组成和钙长石含量与布什维尔德杂岩体中其他地方的梅伦斯基和巴斯塔德循环单元的数据进行比较，支持这样的论点：Flatreef 是上临界带 - 主带过渡的相关物，包括Merensky 和 ​​Bastard 循环单元。现有数据表明，Flatreef 及其相关物在布什维尔德复合体其余部分的硫化物最初形成于更深的分期室。在持续的岩浆上升过程中，一些硫化物被夹带并沉积在 Flatreef 中。将穿过该交叉点的斜长石的 Sr 同位素组成和钙长石含量与布什维尔德杂岩体中其他地方的梅伦斯基和巴斯塔德循环单元的数据进行比较，支持这样的论点：Flatreef 是上临界带 - 主带过渡的相关物，包括Merensky 和 ​​Bastard 循环单元。现有数据表明，Flatreef 及其相关物的硫化物在布什维尔德复合体的其余部分最初形成于一个更深的分期室。在持续的岩浆上升过程中，一些硫化物被夹带并沉积在 Flatreef 中。