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In situ elemental and Sr isotope characteristics of magmatic to hydrothermal minerals from the Black Mountain porphyry deposit, Baguio District, Philippines

Cao Mingjian, Pete Hollings, Noreen J. Evans, David R. Cooke, Brent I. A. McInnes, Zhao Kuidong, Qin Kezhang, Li Dengfeng and Gabe Sweet
In situ elemental and Sr isotope characteristics of magmatic to hydrothermal minerals from the Black Mountain porphyry deposit, Baguio District, Philippines
Economic Geology and the Bulletin of the Society of Economic Geologists (December 2019) 115 (4): 927-944

Abstract

At the Black Mountain porphyry Cu-Au deposit in the Baguio district, Northern Luzon (Philippines), pre- and synmineralized rocks preserve magmatic and hydrothermal minerals (e.g., plagioclase, amphibole, titanite, and epidote) spanning the complete paragenesis of the deposit. Strontium isotope values in early crystallized plagioclase phenocrysts from all felsic porphyries can be divided into two types. The type-I plagioclase crystals show relatively homogeneous Sr isotope values (0.7035-0.7038, 1sigma <0.0001), indicating crystallization from a relatively stable and long-lived felsic magma chamber. The type-II plagioclase grains have a wider range of Sr isotope compositions (0.7032-0.7039, 1sigma <0.0001), indicating mafic and/or felsic magma recharge. In magmatic titanite, Nb/Ta values are higher than those in the whole rock, while Zr/Hf and Y/Ho values are lower. In hydrothermal titanite and epidote, the ratios are similar to those in the whole rock. These patterns reflect crystallization effects imposed during the magmatic stage but an absence of differentiation during the hydrothermal stage. The consistent gradual decrease in total rare earth element, Y, Zr, and U contents in both hydrothermal titanite and epidote from early to late stages indicates the effect of hydrothermal fluid evolution with decreasing temperature. The variation of (super 87) Sr/ (super 86) Sr values in magmatic amphibole, plagioclase, and hydrothermal epidote in felsic and mafic rocks indicates the addition of mafic magma-derived fluid into the felsic magma-derived fluid. One extra source of fluid (probably derived from wall-rock limestone) was required to generate the highly radiogenic (super 87) Sr/ (super 86) Sr values of some epidote (0.7038-0.7053). Thus, in situ elemental and Sr isotope variation in minerals from different paragenetic stages can be used to interpret formation process and source for both magmas and hydrothermal fluids.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 115
Serial Issue: 4
Title: In situ elemental and Sr isotope characteristics of magmatic to hydrothermal minerals from the Black Mountain porphyry deposit, Baguio District, Philippines
Affiliation: Chinese Academy of Sciences, Institute of Geology and Geophysics, Key Laboratory of Mineral Resources, Beijing, China
Pages: 927-944
Published: 20191217
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 64
Accession Number: 2020-011802
Categories: Economic geology, geology of ore depositsIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 2 tables, geol. sketch map
N16°00'00" - N17°00'00", E120°30'00" - E121°30'00"
Secondary Affiliation: Lakehead University, Geology Department, CAN, CanadaCurtin University, School of Earth and Planetary Science/John de Laeter Centre, AUS, AustraliaUniversity of Tasmania, Transforming the Mining Value Chain, an Australia Research Council Industrial Transformation Research Hub, AUS, AustraliaChina University of Geosciences, School of Earth Resources, Collaborative Innovation Center for Exploration of Strategic Mineral Resources, State Key Laboratory of Geological Processes and Mineral Resources, CHN, ChinaSun Yat-sen University, School of Marine Sciences, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202009
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