| 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
Takahashi, Ryohei
Imai, Akira
Parcon-Calamohoy, Rhyza Ruth
Santos Mervinde los
Subang, Leo
Alburo, Glenn Christian
|
| 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/). |
kokuA_2022_5.pdf (39.9 MB)
