The Central African Copperbelt stands out as one of the world's largest sediment-hosted Cu-Co provinces, contributing to over 60% of global Co production. A comprehensive basin analysis approach is imperative for unraveling the ore-forming processes, encompassing an understanding of the diagenesis or metamorphism that the mineralized rocks underwent. In this study, two types of pyrobitumen (burial related and burial plus hydrothermal related) reflectance values have been measured, which record maximum temperatures during deep burial and hydrothermal imprint. The calculated temperatures provide important information about the maximum burial and hydrothermal fluid temperatures in distinct regions of the Copperbelt. The average burial related pyrobitumen reflectance for Nkana, the southeastern part of the Copperbelt, ranges between 3.43 and 3.75% BR, indicating a maximum burial temperature of about 240 °C. Moving towards the central part of the Copperbelt at Luiswishi, the average pyrobitumen reflectance varies between 2.65 and 2.87% BR, with calculated maximum burial temperatures reaching about 220 °C. In the northwestern part (Tenke Fungurume mining district, TFMD), the maximum burial temperatures decrease to approximately 200 °C, based on the calculation of pyrobitumen reflectance at 2.10% BR. This decreasing temperature trend from southeast to northwest corresponds to the observed decrease in metamorphic grade across the Copperbelt, ranging from amphibolite and upper greenschist facies in the Zambian part to prehnite-pumpellyite facies in the Congolese Copperbelt. The temperatures calculated during maximum burial, especially at the Nkana ore deposit, are lower than those previously proposed based on the mineralogy of the rocks, i.e. upper greenschist facies. However, the latter does correspond to the temperatures reached by the mineralizing fluids in this area and thus rather reflects the alteration assemblage and temperature. The average burial plus hydrothermal related pyrobitumen reflectance measured at TFMD ranges between 3.06 and 5.36% BR, indicating calculated average temperatures of 300–350 °C. These temperatures align with those recorded for the late diagenetic to syn-orogenic mineralization by fluid inclusion microthermometry (180–340 °C) at TFMD. The data suggests a pervasive migration of hydrothermal fluid through the rocks, contributing to the observed pyrobitumen reflectance. The illite crystallinity of the examined samples is notably high. At Nkana, the KI values range between 0.10 Δ°2θ and 0.22 Δ°2θ, for Luiswishi between 0.12 Δ°2θ and 0.24 Δ°2θ, for Kamoto between 0.17 Δ°2θ and 0.23 Δ°2θ, for TFMD between 0.17 Δ°2θ and 0.25 Δ°2θ, which indicates all these samples were placed in epizone, with only a few in anchizone. This high value could be attributed to two potential factors: the admixing of detrital muscovite to the sediments or the influx of potassium due to the pervasive alteration throughout the Copperbelt, but the latter one is less likely since the selected samples show no evidence of alteration.

中文翻译：

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中非铜带的成岩作用和矿化，焦沥青反射率和库伯勒（伊利石结晶度）指数的影响


中非铜矿带是世界上最大的沉积物铜钴省之一，占全球钴产量的 60% 以上。全面的盆地分析方法对于阐明成矿过程至关重要，包括了解矿化岩石所经历的成岩作用或变质作用。在这项研究中，测量了两种类型的焦沥青（埋藏相关和埋藏加热液相关）反射率值，记录了深埋和热液印记期间的最高温度。计算出的温度提供了有关铜带不同区域的最大埋藏温度和热液温度的重要信息。铜带东南部的恩卡纳与埋藏相关的平均焦沥青反射率范围在 3.43% BR 和 3.75% BR 之间，表明最高埋藏温度约为 240 °C。向 Luiswishi 的铜带中部移动，平均焦沥青反射率在 2.65% 到 2.87% BR 之间变化，计算出的最高埋藏温度达到约 220 °C。在西北部（Tenke Fungurume 矿区，TFMD），根据 2.10% BR 的焦沥青反射率计算，最高埋藏温度降至约 200 °C。这种从东南到西北的温度下降趋势与观察到的整个铜矿带变质程度的降低相对应，范围从赞比亚部分的角闪岩和上部绿片岩相到刚果铜矿带的葡萄石-半辉石相。最大埋藏期间计算的温度，尤其是恩卡纳矿床的温度，低于之前根据岩石矿物学（即上部绿片岩相）提出的温度。 然而，后者确实对应于该区域矿化流体所达到的温度，因此更能反映蚀变组合和温度。在 TFMD 测量的平均埋藏加热液相关的焦沥青反射率范围在 3.06% BR 和 5.36% BR 之间，表明计算出的平均温度为 300–350 °C。这些温度与 TFMD 流体包裹体显微测温 (180–340 °C) 记录的晚期成岩至同造山矿化温度一致。数据表明热液在岩石中普遍迁移，导致了所观察到的焦沥青反射率。所检测样品的伊利石结晶度非常高。在 Nkana，KI 值范围在 0.10 Δ°2θ 和 0.22 Δ°2θ 之间，Luiswishi 在 0.12 Δ°2θ 和 0.24 Δ°2θ 之间，Kamoto 在 0.17 Δ°2θ 和 0.23 Δ°2θ 之间，TFMD 在 0.17 Δ° 之间2θ 和 0.25 Δ°2θ，这表明所有这些样品都放置在 epizone 中，只有少数样品放置在 anchizone 中。这一高值可能归因于两个潜在因素：碎屑白云母与沉积物的混合，或者由于整个铜带的普遍蚀变而导致钾的流入，但后一种可能性较小，因为所选样品没有显示出蚀变的证据。