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  1. 40 国際資源学研究科・国際資源学部
  2. 40A 学術誌論文
  3. 40A1 雑誌掲載論文

Heterogeneity of mineral chemistry and sulfur isotopic composition of alunite in the Mankayan lithocap, northern Luzon, Philippines

http://hdl.handle.net/10295/00006095
http://hdl.handle.net/10295/00006095
3dd2a601-d2d4-4e81-bc07-35ae20ac7c12
名前 / ファイル ライセンス アクション
kokuA_2022_5.pdf kokuA_2022_5.pdf (39.9 MB)
Item type 学術雑誌論文 / Journal Article(1)
公開日 2022-10-27
タイトル
タイトル Heterogeneity of mineral chemistry and sulfur isotopic composition of alunite in the Mankayan lithocap, northern Luzon, Philippines
言語 en
言語
言語 eng
主題
主題Scheme Other
主題 Alunite
主題
主題Scheme Other
主題 Natroalunite
主題
主題Scheme Other
主題 High-sulfidation
主題
主題Scheme Other
主題 Quartz-pyrite-gold
主題
主題Scheme Other
主題 Sulfur isotopes
主題
主題Scheme Other
主題 Mankayan
主題
主題Scheme Other
主題 Luzon
主題
主題Scheme Other
主題 Lepanto
資源タイプ
資源タイプ識別子 http://purl.org/coar/resource_type/c_6501
資源タイプ journal article
アクセス権
アクセス権 open access
アクセス権URI http://purl.org/coar/access_right/c_abf2
作成者 Manalo, Pearlyn

× Manalo, Pearlyn

en Manalo, Pearlyn

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Takahashi, Ryohei

× Takahashi, Ryohei

en Takahashi, Ryohei

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Imai, Akira

× Imai, Akira

en Imai, Akira

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Parcon-Calamohoy, Rhyza Ruth

× Parcon-Calamohoy, Rhyza Ruth

en Parcon-Calamohoy, Rhyza Ruth

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Santos Mervinde los

× Santos Mervinde los

en Santos Mervinde los

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Subang, Leo

× Subang, Leo

en Subang, Leo

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Alburo, Glenn Christian

× Alburo, Glenn Christian

en Alburo, Glenn Christian

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内容記述
内容記述タイプ Abstract
内容記述 The lithocap at Mankayan is a contiguous zone of alunite + quartz + pyrite that occur as pervasive alteration of the metavolcanic basement and dacitic pyroclastic rocks. Alunite + quartz + pyrite assemblage also occurs within hydrothermal gold-bearing veins and breccias. Several high-sulfidation epithermal gold orebodies have been previously delineated in the Lepanto Main Enargite orebody, and in the Northwest, Carmen, Florence West and Florence East quartz-pyrite-gold (QPG) veins. This study presents new data of mineral composition and sulfur isotopic ratios of alunites from different zones of the lithocap at Mankayan. Elemental composition maps and point analysis of alunites indicate compositional heterogeneity within a single alunite crystal. Common substituents to the K+ site are Na+ and H3O+, with few Ca2+ substitution in some sites. Limited occurrences of PO43- substitution to SO42- were also documented. Sulfur isotopic ratios (δ34SCDT) of alunite range from + 13 ‰ to + 24 ‰, which are typical of hypogene alunite. Sulfur isotopic ratios of coexisting pyrite are mostly negative, ranging from −5.4 to −1.0 ‰. Few samples of alunite from the Northwest and Florence West quartz-pyrite-gold veins have sulfur isotopic ratios similar to the values of its coexisting pyrite. The estimated temperature of formation using sulfur isotope geothermometry of alunite-pyrite pairs ranges from 197 °C to 364 °C, with most of the samples varying within 220 to 270 °C. The calculated bulk δ34S of the hydrothermal fluid was found to be + 5 to + 6 ‰ for the different mineralization events in Mankayan. The alunite crystals are heterogeneous even in the microscopic scale. Compositional maps show that K and Na concentration vary within single crystals, as well as among different crystals of a sample. The variations of K and Na content mostly follow the crystal growth structure, however, some alunite crystals with irregular variations are also present. Some samples contain aluminum-phosphate-sulfate (APS) minerals intergrown with alunite. Electron probe microanalysis of the alunite crystals showed a generally wide range of composition between the alunite – natroalunite solid solution. Using thermodynamic functions, a relationship between temperature and K+/Na+ of the hydrothermal fluids was determined across the range of alunite-natroalunite solid solution system. The model curves suggest that at temperatures less than ∼ 250 °C a slight change in fluid composition and/or temperature can vary the number of Na atoms per formula unit by 0.3 units. At higher temperatures, a more significant change in the physicochemical conditions is required for a substitution to occur. This explains the wide range of Na content in the alunites from the different parts of the lithocap. The characteristics compiled in this study reflect the fluctuations in temperature and fluid compositions that occurred during the multiple hydrothermal events in the Mankayan District.
言語 en
出版タイプ
出版タイプ VoR
出版タイプResource http://purl.org/coar/version/c_970fb48d4fbd8a85
書誌情報 en : Ore Geology Reviews

巻 146, 発行日 2022
収録物識別子
収録物識別子タイプ ISSN
収録物識別子 00396060
出版者
出版者 Elsevier B.V.
関連情報
識別子タイプ DOI
関連識別子 https://doi.org/10.1016/j.oregeorev.2022.104959
権利情報
権利情報 © 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
nc-nd/4.0/).
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