The proximity to metasedimentary footwall rocks relative to platinum group element (PGE) mineralized intrusive rocks in the northern limb of the Bushveld Igneous Complex (BIC) has resulted in complex local contamination in the intrusions. To assess the extent of incorporation of non-magmatic material and its effects on PGE mineralization, major element, trace element, and S isotopic data were collected from drill core UMT094 on the Turfspruit farm, where core logging has shown that the mineralized Platreef, forming the Flatreef deposit, is located stratigraphically well above local sedimentary footwall rocks. The S isotopic data combined with whole rock geochemistry data (including CaO/Al 2 O 3 , (V/Ti) PM , (Ni/Cr) PM , S/Se, loss on ignition) were used to assess incorporation of a range of local footwall material. The δ 34 S data show a steady decrease from the footwall assimilation zone (δ 34 S typically + 8 to + 9‰, maximum 12‰) to near constant δ 34 S values (δ 34 S < + 4‰) below the main PGE reef. Similar values have been documented for the Merensky Reef in the eastern and western limbs of the BIC (δ 34 S ~ 0 to + 3.5‰). Other geochemical parameters, such as S/Se and CaO/Al 2 O 3 , also match the ranges documented for the Merensky Reef elsewhere in the BIC. In addition, parameters such as whole rock V/Ti, normalized to primitive mantle (V/Ti) PM , are shown to be useful indicators of contamination and the type of contaminant with 1 < (V/Ti) PM < 2 for uncontaminated magmatic units; [V/Ti] pm > 2 for shale assimilation; and [V/Ti] pm < 1 for carbonate assimilation. The results suggest that the main PGE mineralization in the Flatreef deposit formed without significant in situ contamination and that the primary mechanism of PGE mineralization in the Platreef at Turfspruit was no different than the mechanism that generated the Merensky Reef in the eastern and western limbs of the BIC.

中文翻译：

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使用硫同位素和微量元素地球化学评估 Flatreef、Bushveld 火成岩杂岩体北翼的局部地壳同化程度

Bushveld 火成岩杂岩体 (BIC) 北翼中与铂族元素 (PGE) 矿化侵入岩相关的变质沉积下盘岩石导致侵入体中复杂的局部污染。为了评估非岩浆物质的掺入程度及其对 PGE 矿化的影响，从 Turfspruit 农场的钻芯 UMT094 中收集了主要元素、微量元素和 S 同位素数据，其中岩心测井表明矿化 Platreef，形成Flatreef 矿床位于当地沉积下盘岩上方的地层上。S 同位素数据结合全岩地球化学数据（包括 CaO/Al 2 O 3 、(V/Ti) PM 、(Ni/Cr) PM 、S/Se、烧失量）用于评估一系列当地下墙材料。δ 34 S 数据显示从下盘同化带（δ 34 S 通常为 + 8 到 + 9‰，最大值为 12‰）到主要 PGE 以下的接近恒定的 δ 34 S 值（δ 34 S < + 4‰）稳定下降礁。在 BIC 东部和西部的 Merensky 礁也有类似的记录（δ 34 S ~ 0 到 + 3.5‰）。其他地球化学参数，如 S/Se 和 CaO/Al 2 O 3 ，也与 BIC 其他地方记录的梅伦斯基礁的范围相匹配。此外，全岩 V/Ti 等参数，归一化为原始地幔 (V/Ti) PM ，被证明是污染和污染物类型的有用指标，对于未受污染的岩浆，1 < (V/Ti) PM < 2单位; [V/Ti] pm > 2 对于页岩同化；和 [V/Ti] pm < 1 用于碳酸盐同化。