Titanium‐in‐biotite thermometry in porphyry copper systems: Challenges to application of the thermometer

IF 1.1 4区 地球科学 Q3 GEOLOGY
Resource Geology Pub Date : 2019-12-27 DOI:10.1111/rge.12227
M. Rezaei, A. Zarasvandi
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引用次数: 12

Abstract

Empirical geothermometer dealing with Ti solubility in the Fe‐Mg biotites was originally proposed for biotites in graphitic, peraluminous metapelites containing ilmenite or rutile that equilibrated roughly at 4–6 kbar. Given that biotites are abundant in the porphyry copper systems, this geothermometer has frequently been used for the determination of magmatic–hydrothermal temperatures in the porphyry copper systems. Common associations of porphyry copper deposits (PCDs), that is, low Al content of biotite, biotite chloritization (causes the biotite to become more magnesian and to lose Ti), and biotite formation by amphibole replacement, as well as disequilibrium, local equilibrium, or re‐equilibration of biotites, especially through potassic alteration, may provide significant uncertainty in the temperatures estimated a by Ti‐in‐biotite geothermometer. In addition, besides the calibration range of thermometer for pressure (400–600 MPa), the temperatures of major sulfide precipitation in PCDs (>~400°C) does not fit with the temperature range of thermometer calibration (480–800°C). Worth noting, as confirmed by fluid inclusion data in the Sarkuh PCD, regardless of presence of mineralogical requirements, obtained temperatures of sulfide mineralization using Ti in biotite thermometer could be overestimated. This may be due to the difference between general conditions of sulfide mineralization and calibration range of Ti in the biotite thermometer for pressure and temperature, as well as the metaluminous nature of biotites in PCDs.
斑岩-铜系统中钛-黑云母测温:温度计应用的挑战
研究钛在Fe - Mg黑云母中的溶解度的经验地温计最初是针对含有钛铁矿或金红石的石墨、过铝质偏长石中的黑云母提出的,这些偏长石的平衡温度大致在4-6 kbar。由于斑岩铜体系中含有丰富的黑云母,该地温计常用于测定斑岩铜体系中的岩浆热液温度。斑岩铜矿(PCDs)的共同关联,即黑云母的低铝含量,黑云母的绿泥化(导致黑云母变得更镁化并失去钛),以及角闪孔替代形成的黑云母,以及黑云母的不平衡、局部平衡或再平衡,特别是通过钾蚀变,可能会给Ti - in -黑云母地温计估算的温度提供显著的不确定性。此外,除了压力温度计的校准范围(400 - 600 MPa)外,PCDs中主要硫化物沉淀的温度(>~400℃)不符合温度计校准温度范围(480-800℃)。值得注意的是,正如Sarkuh PCD中的流体包裹体数据所证实的那样,无论是否存在矿物学要求,使用黑云母Ti温度计获得的硫化物矿化温度都可能被高估。这可能是由于硫化物矿化的一般条件与黑云母温度计中钛的压力和温度校准范围存在差异,以及PCDs中黑云母的铝质性质。
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来源期刊
Resource Geology
Resource Geology 地学-地质学
CiteScore
2.30
自引率
14.30%
发文量
18
审稿时长
12 months
期刊介绍: Resource Geology is an international journal focusing on economic geology, geochemistry and environmental geology. Its purpose is to contribute to the promotion of earth sciences related to metallic and non-metallic mineral deposits mainly in Asia, Oceania and the Circum-Pacific region, although other parts of the world are also considered. Launched in 1998 by the Society for Resource Geology, the journal is published quarterly in English, making it more accessible to the international geological community. The journal publishes high quality papers of interest to those engaged in research and exploration of mineral deposits.
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