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<title>UTas ePrints - Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition</title>
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<meta content="Cooke, D.R." name="eprints.creators_name" />
<meta content="McPhail, D.C." name="eprints.creators_name" />
<meta content="David.Cooke@utas.edu.au" name="eprints.creators_id" />
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<meta content="2007-09-14" name="eprints.datestamp" />
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<meta content="Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition " name="eprints.title" />
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<meta content="260100" name="eprints.subjects" />
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<meta content="epithermal, gold, silver, telluride, gas, transport" name="eprints.keywords" />
<meta content="In this study, we discuss the effects of cooling, boiling, fluid mixing, and water-rock interaction on a lowsulfidation
chloride water. Our water composition is derived from fluid inclusion and mineralogical studies of the Acupan gold mine, a large gold-silver-tellurium-bearing low-sulfidation epithermal deposit in the Philippines.
Our numerical modeling results show that a single mineralizing water (300 degrees C, 0.5 wt % NaCl + KCl,
0.41 m CO2) will evolve along different reaction pathways in response to different physicochemical processes,
and that these pathways are difficult to predict intuitively in many cases. Acidity and redox can evolve dramatically and in different directions, with boiling resulting in oxidation and pH increase, cooling resulting in pH decrease at a relatively constant sulfate/sulfide ratio, and mixing with sulfate-bearing ground waters causing oxidation and acidification.
Based on the correlation of predicted and observed ore and gangue minerals, boiling is concluded to have
resulted in the deposition of most of the precious and base metals at Acupan. Continuous boiling, boiling with
intermittent gas loss, and throttling probably all occurred at various times during the evolution of the hydrothermal
system. The loss of gases during boiling (e.g., H2S, H2Te, Te2) enhanced electrum and base metal sulfide
deposition and inhibited the precipitation of hessite and calaverite. Mixing of low-temperature ground
waters with the high-temperature chloride water resulted in mineral assemblages that are similar to those
observed in shallow levels of the mine and in deep-level, late-stage barren vein fill. Mixing with ground water
could account for the observed transition from adularia-carbonate vein assemblages in deep mine levels to
sericite-bearing assemblages in shallow levels. Late-stage anhydrite could have formed via mixing with or heating
of near-surface ground waters.
We predict tellurium to be transported preferentially in a gas phase. Because tellurium solubilities are predicted
to be low in auriferous chloride waters, telluride and native tellurium deposition in low-sulfidation environments
may result from condensation of magmatically derived H2Te(g) and Te2(g) into deep-level chloride waters. The minor amount of tellurium that dissolves into chloride waters will be deposited effectively by cooling or fluid mixing. Aqueous tellurium will partition strongly into the gas phase in boiling low-sulfidation systems and could precipitate via condensation into lower temperature ground waters. This could lead to vertical zonation of electrum and tellurium-bearing minerals, which may be of significance to mineral exploration." name="eprints.abstract" />
<meta content="2001" name="eprints.date" />
<meta content="published" name="eprints.date_type" />
<meta content="Economic Geology" name="eprints.publication" />
<meta content="96" name="eprints.volume" />
<meta content="1" name="eprints.number" />
<meta content="109-131" name="eprints.pagerange" />
<meta content="10.2113/96.1.109" name="eprints.id_number" />
<meta content="UNSPECIFIED" name="eprints.thesis_type" />
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<meta content="0361-0128" name="eprints.issn" />
<meta content="http://dx.doi.org/10.2113/96.1.109" name="eprints.official_url" />
<meta content="Afifi, A.M., Kelly, W.C., and Essene, E.J., 1988, Phase relations among tellurides, sulfides, and oxides: II. Applications to telluride-bearing ore deposits:
ECONOMIC GEOLOGY, v. 83, p. 395-404.
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Aoki, M., Comsti, E.C., Lazo, F.B., and Matsuhisha, Y., 1993, Advanced argillic alteration and geochemistry of alunite in an evolving hydrothermal system at Baguio, northern Luzon, Philippines: Resource Geology, v. 43, p.
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Berman, R.G., 1988, Internally consistent thermodynamic data for minerals in the system Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-SiO2-TiO2-H2OCO2: Journal of Petrology, v. 29, p. 445-522.
Callow, K.J., and Worley, B.W., Jr., 1965, The occurrence of telluride minerals at the Acupan gold mine, Mountain Province, Philippines: ECONOMIC GEOLOGY, v. 60, p. 251-268.
Cooke, D.R., 1991, Styles and controls of mineralization, Acupan gold mine, Baguio district, Philippines: Unpublished Ph.D. thesis, Melbourne, Australia, Monash University, 396 p.
Cooke, D.R., and Bloom, M.S., 1990, Epithermal and subjacent porphyry mineralization, Acupan, Baguio District, Philippines: A fluid-inclusion and paragenetic study: Journal of Geochemical Exploration, v. 35, p. 297-340.
Cooke, D.R., and Simmons, S.F., 2000, Characteristics and genesis of epithermal gold deposits: Reviews in Economic Geology, v. 13, p. 221-244.
Cooke, D.R., McPhail, D.C., and Bloom, M.S., 1996, Epithermal gold mineralization, Acupan, Baguio district, Philippines: Geology, mineralization, alteration, and the thermochemical environment of ore deposition: ECONOMIC
GEOLOGY, v. 91, p. 243-272.
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v. 84, p. 328-359.
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<meta content="Cooke, D.R. and McPhail, D.C. (2001) Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition. Economic Geology, 96 (1). pp. 109-131. ISSN 0361-0128" name="eprints.citation" />
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<meta content="Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition " name="DC.title" />
<meta content="Cooke, D.R." name="DC.creator" />
<meta content="McPhail, D.C." name="DC.creator" />
<meta content="260100 Geology" name="DC.subject" />
<meta content="In this study, we discuss the effects of cooling, boiling, fluid mixing, and water-rock interaction on a lowsulfidation
chloride water. Our water composition is derived from fluid inclusion and mineralogical studies of the Acupan gold mine, a large gold-silver-tellurium-bearing low-sulfidation epithermal deposit in the Philippines.
Our numerical modeling results show that a single mineralizing water (300 degrees C, 0.5 wt % NaCl + KCl,
0.41 m CO2) will evolve along different reaction pathways in response to different physicochemical processes,
and that these pathways are difficult to predict intuitively in many cases. Acidity and redox can evolve dramatically and in different directions, with boiling resulting in oxidation and pH increase, cooling resulting in pH decrease at a relatively constant sulfate/sulfide ratio, and mixing with sulfate-bearing ground waters causing oxidation and acidification.
Based on the correlation of predicted and observed ore and gangue minerals, boiling is concluded to have
resulted in the deposition of most of the precious and base metals at Acupan. Continuous boiling, boiling with
intermittent gas loss, and throttling probably all occurred at various times during the evolution of the hydrothermal
system. The loss of gases during boiling (e.g., H2S, H2Te, Te2) enhanced electrum and base metal sulfide
deposition and inhibited the precipitation of hessite and calaverite. Mixing of low-temperature ground
waters with the high-temperature chloride water resulted in mineral assemblages that are similar to those
observed in shallow levels of the mine and in deep-level, late-stage barren vein fill. Mixing with ground water
could account for the observed transition from adularia-carbonate vein assemblages in deep mine levels to
sericite-bearing assemblages in shallow levels. Late-stage anhydrite could have formed via mixing with or heating
of near-surface ground waters.
We predict tellurium to be transported preferentially in a gas phase. Because tellurium solubilities are predicted
to be low in auriferous chloride waters, telluride and native tellurium deposition in low-sulfidation environments
may result from condensation of magmatically derived H2Te(g) and Te2(g) into deep-level chloride waters. The minor amount of tellurium that dissolves into chloride waters will be deposited effectively by cooling or fluid mixing. Aqueous tellurium will partition strongly into the gas phase in boiling low-sulfidation systems and could precipitate via condensation into lower temperature ground waters. This could lead to vertical zonation of electrum and tellurium-bearing minerals, which may be of significance to mineral exploration." name="DC.description" />
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<h1 class="ep_tm_pagetitle">Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition</h1>
<p style="margin-bottom: 1em" class="not_ep_block"><span class="person_name">Cooke, D.R.</span> and <span class="person_name">McPhail, D.C.</span> (2001) <xhtml:em>Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition.</xhtml:em> Economic Geology, 96 (1). pp. 109-131. ISSN 0361-0128</p><p style="margin-bottom: 1em" class="not_ep_block"></p><table style="margin-bottom: 1em" class="not_ep_block"><tr><td valign="top" style="text-align:center"><a href="http://eprints.utas.edu.au/1940/1/Cooke_McPhail_ECON_GEOL_2001.pdf"><img alt="[img]" src="http://eprints.utas.edu.au/style/images/fileicons/application_pdf.png" border="0" class="ep_doc_icon" /></a></td><td valign="top"><a href="http://eprints.utas.edu.au/1940/1/Cooke_McPhail_ECON_GEOL_2001.pdf"><span class="ep_document_citation">PDF</span></a> - Full text restricted - Requires a PDF viewer<br />372Kb</td><td><form method="get" accept-charset="utf-8" action="http://eprints.utas.edu.au/cgi/request_doc"><input value="2421" name="docid" accept-charset="utf-8" type="hidden" /><div class=""><input value="Request a copy" name="_action_null" class="ep_form_action_button" onclick="return EPJS_button_pushed( '_action_null' )" type="submit" /> </div></form></td></tr></table><p style="margin-bottom: 1em" class="not_ep_block">Official URL: <a href="http://dx.doi.org/10.2113/96.1.109">http://dx.doi.org/10.2113/96.1.109</a></p><div class="not_ep_block"><h2>Abstract</h2><p style="padding-bottom: 16px; text-align: left; margin: 1em auto 0em auto">In this study, we discuss the effects of cooling, boiling, fluid mixing, and water-rock interaction on a lowsulfidation
chloride water. Our water composition is derived from fluid inclusion and mineralogical studies of the Acupan gold mine, a large gold-silver-tellurium-bearing low-sulfidation epithermal deposit in the Philippines.
Our numerical modeling results show that a single mineralizing water (300 degrees C, 0.5 wt % NaCl + KCl,
0.41 m CO2) will evolve along different reaction pathways in response to different physicochemical processes,
and that these pathways are difficult to predict intuitively in many cases. Acidity and redox can evolve dramatically and in different directions, with boiling resulting in oxidation and pH increase, cooling resulting in pH decrease at a relatively constant sulfate/sulfide ratio, and mixing with sulfate-bearing ground waters causing oxidation and acidification.
Based on the correlation of predicted and observed ore and gangue minerals, boiling is concluded to have
resulted in the deposition of most of the precious and base metals at Acupan. Continuous boiling, boiling with
intermittent gas loss, and throttling probably all occurred at various times during the evolution of the hydrothermal
system. The loss of gases during boiling (e.g., H2S, H2Te, Te2) enhanced electrum and base metal sulfide
deposition and inhibited the precipitation of hessite and calaverite. Mixing of low-temperature ground
waters with the high-temperature chloride water resulted in mineral assemblages that are similar to those
observed in shallow levels of the mine and in deep-level, late-stage barren vein fill. Mixing with ground water
could account for the observed transition from adularia-carbonate vein assemblages in deep mine levels to
sericite-bearing assemblages in shallow levels. Late-stage anhydrite could have formed via mixing with or heating
of near-surface ground waters.
We predict tellurium to be transported preferentially in a gas phase. Because tellurium solubilities are predicted
to be low in auriferous chloride waters, telluride and native tellurium deposition in low-sulfidation environments
may result from condensation of magmatically derived H2Te(g) and Te2(g) into deep-level chloride waters. The minor amount of tellurium that dissolves into chloride waters will be deposited effectively by cooling or fluid mixing. Aqueous tellurium will partition strongly into the gas phase in boiling low-sulfidation systems and could precipitate via condensation into lower temperature ground waters. This could lead to vertical zonation of electrum and tellurium-bearing minerals, which may be of significance to mineral exploration.</p></div><table style="margin-bottom: 1em" border="0" cellpadding="3" class="not_ep_block"><tr><th valign="top" class="ep_row">Item Type:</th><td valign="top" class="ep_row">Article</td></tr><tr><th valign="top" class="ep_row">Keywords:</th><td valign="top" class="ep_row">epithermal, gold, silver, telluride, gas, transport</td></tr><tr><th valign="top" class="ep_row">Subjects:</th><td valign="top" class="ep_row"><a href="http://eprints.utas.edu.au/view/subjects/260100.html">260000 Earth Sciences > 260100 Geology</a></td></tr><tr><th valign="top" class="ep_row">Collections:</th><td valign="top" class="ep_row">UNSPECIFIED</td></tr><tr><th valign="top" class="ep_row">ID Code:</th><td valign="top" class="ep_row">1940</td></tr><tr><th valign="top" class="ep_row">Deposited By:</th><td valign="top" class="ep_row"><span class="ep_name_citation"><span class="person_name">Mrs Katrina Keep</span></span></td></tr><tr><th valign="top" class="ep_row">Deposited On:</th><td valign="top" class="ep_row">14 Sep 2007</td></tr><tr><th valign="top" class="ep_row">Last Modified:</th><td valign="top" class="ep_row">24 Jan 2008 12:18</td></tr><tr><th valign="top" class="ep_row">ePrint Statistics:</th><td valign="top" class="ep_row"><a target="ePrintStats" href="/es/index.php?action=show_detail_eprint;id=1940;">View statistics for this ePrint</a></td></tr></table><p align="right">Repository Staff Only: <a href="http://eprints.utas.edu.au/cgi/users/home?screen=EPrint::View&eprintid=1940">item control page</a></p>
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