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New Advances in Detecting the Distal Geochemical Footprints of Porphyry Systems— Epidote Mineral Chemistry as a Tool for Vectoring and Fertility Assessments
Citation
Cooke, DR and Baker, M and Hollings, P and Sweet, G and Chang, Z and Danyushevsky, L and Gilbert, S and Zhou, T and White, NC and Gemmell, JB and Inglis, S, New Advances in Detecting the Distal Geochemical Footprints of Porphyry Systems Epidote Mineral Chemistry as a Tool for Vectoring and Fertility Assessments, Building Exploration Capability for the 21st Century, Colt Print Services, KD Kelley, HC Golden (ed), Colorado, USA, pp. 127-152. ISBN 978-1-629491-424 (2014) [Research Book Chapter]
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Copyright 2014 Society of Economic Geologists, Inc.
Official URL: https://segweb.org/store_info/SP/SP-18-Additional-...
Abstract
Propylitic alteration halos to porphyry deposits are characterized by low- to moderate-intensity replacements
of primary feldspars and mafic minerals by epidote, chlorite, calcite ± actinolite, pyrite, prehnite, and zeolites.
The pyrite halo that surrounds porphyry deposits typically extends part way through the propylitic halo and provides
strong responses to conventional geochemical and geophysical exploration techniques. When exploring
outside of the pyrite halo, porphyry deposits have proven to be difficult to detect based simply on the presence
of weak epidote-chlorite alteration.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of epidote from propylitic alteration zones around porphyry and skarn deposits in the central Baguio district, Philippines, have shown that low-level hypogene geochemical dispersion halos can be detected at considerably greater distances than can be achieved by conventional rock chip sampling of altered rocks. Epidote chemistry can provide vectoring information to the deposit center and potentially provides insights into the potential metal endowment of the porphyry system, providing explorers with both vectoring and fertility assessment tools.
Epidote chemistry varies with respect to distance from porphyry deposit centers, with the highest concentrations of proximal pathfinder elements (e.g., Cu, Mo, Au, Sn) detected in epidote from close to the potassic alteration zone. Distal pathfinder elements (e.g., As, Sb, Pb, Zn, Mn) are most enriched in epidote more than 1.5 km from the deposit center. Rare earth elements and Zr are most enriched in epidote from the edge of the pyrite halo. The lateral zonation in epidote chemistry implies that at Baguio the geochemical dispersion patterns were produced by lateral outflow of spent fluids from the porphyry center, rather than from ingress of peripheral, nonmagmatic waters.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of epidote from propylitic alteration zones around porphyry and skarn deposits in the central Baguio district, Philippines, have shown that low-level hypogene geochemical dispersion halos can be detected at considerably greater distances than can be achieved by conventional rock chip sampling of altered rocks. Epidote chemistry can provide vectoring information to the deposit center and potentially provides insights into the potential metal endowment of the porphyry system, providing explorers with both vectoring and fertility assessment tools.
Epidote chemistry varies with respect to distance from porphyry deposit centers, with the highest concentrations of proximal pathfinder elements (e.g., Cu, Mo, Au, Sn) detected in epidote from close to the potassic alteration zone. Distal pathfinder elements (e.g., As, Sb, Pb, Zn, Mn) are most enriched in epidote more than 1.5 km from the deposit center. Rare earth elements and Zr are most enriched in epidote from the edge of the pyrite halo. The lateral zonation in epidote chemistry implies that at Baguio the geochemical dispersion patterns were produced by lateral outflow of spent fluids from the porphyry center, rather than from ingress of peripheral, nonmagmatic waters.
Item Details
| Item Type: | Research Book Chapter |
|---|---|
| Keywords: | exploration, mineral chemistry, epidote, porphyry copper |
| Research Division: | Earth Sciences |
| Research Group: | Geology |
| Research Field: | Ore Deposit Petrology |
| Objective Division: | Mineral Resources (excl. Energy Resources) |
| Objective Group: | Mineral Exploration |
| Objective Field: | Copper Ore Exploration |
| Author: | Cooke, DR (Professor David Cooke) |
| Author: | Baker, M (Dr Michael Baker) |
| Author: | Chang, Z (Dr Zhaoshan Chang) |
| Author: | Danyushevsky, L (Professor Leonid Danyushevsky) |
| Author: | Gilbert, S (Ms Sarah Gilbert) |
| Author: | White, NC (Dr Noel White) |
| Author: | Gemmell, JB (Professor Bruce Gemmell) |
| Author: | Inglis, S (Mr Shaun Inglis) |
| ID Code: | 95960 |
| Year Published: | 2014 |
| Deposited By: | Earth Sciences |
| Deposited On: | 2014-10-13 |
| Last Modified: | 2018-04-04 |
| Downloads: | 3 View Download Statistics |
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