Garry G. Lowder

University of California, Berkeley

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I. S. E. Carmichael

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J. A. S. Dow

GNS Science

Zell E. Peterman

United States Geological Survey

Dow J A S

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GNS Science

United States Geological Survey

Denver Federal Center

Pacific Island Ecosystems Research Center

Colorado School of Mines

United States Government Publishing Office

University of Alberta

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Indra (Spain)

British Academy

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Sr87/Sr86 Ratios of the Talasea Series, New Britain, Territory of New Guinea

Geological Society of America Bulletin (1970)

Zell E. Peterman Garry G. Lowder I. S. E. Carmichael

Research Article| January 01, 1970 Sr87/Sr86 Ratios of the Talasea Series, New Britain, Territory of New Guinea Z. E PETERMAN; Z. E PETERMAN U.S. Geological Surrey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar G. G LOWDER; G. G LOWDER University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar I. S. E CARMICHAEL I. S. E CARMICHAEL University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1970) 81 (1): 39–40. https://doi.org/10.1130/0016-7606(1970)81[39:SROTTS]2.0.CO;2 Article history received: 15 Jul 1969 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Z. E PETERMAN, G. G LOWDER, I. S. E CARMICHAEL; Sr87/Sr86 Ratios of the Talasea Series, New Britain, Territory of New Guinea. GSA Bulletin 1970;; 81 (1): 39–40. doi: https://doi.org/10.1130/0016-7606(1970)81[39:SROTTS]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract No Abstract available This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

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10.1130/0016-7606(1970)81[39:srotts]2.0.co;2

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Geology and exploration of porphyry copper deposits in North Sulawesi, Indonesia

Economic Geology (1978)

Garry G. Lowder J. A. S. Dow

Newly discovered porphyry copper deposits in North Sulawesi (Celebes) are located in two principal districts, each with several centers of porphyry copper mineralization. The deposits were discovered by reconnaissance stream silt geochemistry, which detected anomalies of the order of 500 to 1,000 ppm Cu, against a background of 100 ppm Cu, with anomalous trains extending up to 3 km downstream. Subsequent follow-up revealed stream silt anomalies as high as 1.5 percent Cu. Ore targets were developed by detailed stream silt and rock geochemistry together with geologic mapping of lithology, alteration, sulfide distribution, and quartz veining. Gold proved superior to copper, lead, zinc, and molybdenum in the identification of centers of strongest hypogene mineralization, especially in the case of leached cappings, where a strong gold anomaly accompanied by a weak copper anomaly indicates high potential for supergene-enriched ore at depth.In the economically more important district (Tombuililato) high-level quartz diorite porphyry stocks intrude a middle to upper Tertiary island-arc sequence, consisting principally of andesite and rhyolite. Supergene-enriched mineralization is developed in some of the stocks, which are characterized by intense alteration and generally moderate sulfide contents (3-5 volume percent). Ore-grade hypogene mineralization is restricted to the porphyry and to a narrow andesitic wall-rock contact zone. These copper centers occur within a broad zone (5X15 km) of pyritic mineralization, which is best developed in the Tertiary rhyolitic rocks. In the other district (Tapadaa), copper mineralization occurs in complex dioritic plutons whose sulfide contents, copper grades, and degree of enrichment are generally lower than at Tombuililato.Hydrothermal alteration is characterized by the widespread occurrence of strong advanced argillic alteration and the presence of albite or montmorillonite, rather than potash feldspar, in the ore zone. Advanced argillic mineral assemblages comprise various combinations of quartz, andalusite, corundum, diaspore, pyrophyllite, alunite, kaolinite, and specularite. The highest copper grades are generally accompanied by sericite-albite or sericite-montmorillonite alteration, but biotite, chlorite, magnetite, and some advanced argillic minerals are present at least locally in the ore zone. Copper centers in the Tombuililato district occur within a broad zone of advanced argillic-altered rock which approximately coincides with the pyritic sulfide system. Drilling has shown that ore-grade mineralization underlies some areas of advanced argillic alteration at less than 100 m depth. In some cases this represents a change from advanced argillic to clay-sericite alteration with depth, but ore-grade hypogene copper mineralization does occur with advanced argillic alteration of quartz-diaspore-pyrophyllite type. In this case the total sulfide content is commonly high (3-10 volume percent) and the sulfide assemblage is characteristically pyrite-bornite-chalcopyrite.Exceptional abundance of advanced argillic alteration in North Sulawesi is thought to relate to the presence of albite or montmorillonite instead of potash feldspar, to the dioritic nature of the host rocks, and to unusually acidic ore fluids. Mineralogical data suggest that copper mineralization and alteration in the Tombuililato district may have occurred at relatively low temperatures (350 degrees -400 degrees C). The Tapadaa deposits are thought to be root zones of high-level stocks whose eroded parts were like the deposits now exposed at Tombuililato.

Hypogene

Polymetallic replacement deposit

Diorite

Ore genesis

Supergene (geology)

Argillic alteration

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10.2113/gsecongeo.73.5.628

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Citations (58)

Porphyry copper mineralization at the Tapadaa prospect, northern Sulawesi, Indonesia.

Garry G. Lowder Dow J A S

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The Volcanoes and Caldera of Talasea, New Britain: Geology and Petrology

Geological Society of America Bulletin (1970)

Garry G. Lowder I. S. E. Carmichael

Research Article| January 01, 1970 The Volcanoes and Caldera of Talasea, New Britain: Geology and Petrology G. G LOWDER; G. G LOWDER Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar I. S. E CARMICHAEL I. S. E CARMICHAEL Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1970) 81 (1): 17–38. https://doi.org/10.1130/0016-7606(1970)81[17:TVACOT]2.0.CO;2 Article history received: 21 Apr 1969 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G. G LOWDER, I. S. E CARMICHAEL; The Volcanoes and Caldera of Talasea, New Britain: Geology and Petrology. GSA Bulletin 1970;; 81 (1): 17–38. doi: https://doi.org/10.1130/0016-7606(1970)81[17:TVACOT]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Talasea Peninsula is situated in the New Guinea island arc complex which represents the tectonically active margin of the Australian continent. The peninsula is composed of a chain of Quaternary composite volcanoes and a caldera, with lavas ranging in composition from basalt to rhyolite, although andesite is the dominant variety. The caldera is roughly elliptical in shape, 10 × 13 km, with a volume of collapse of about 75 km3. Located within the caldera are two fault-bounded blocks which appear to be remnants of the ancestral mountain. Post-collapse volcanic activity is found at Mt. Makalia, an andesitic volcano which has developed in the central part of the caldera. It last erupted about 80 years ago. The other volcanoes of the peninsula are largely andesitic composite cones, some of which almost certainly have been active in the last few hundred years. A large area of the peninsula is composed of acid extrusions with an average thickness of 100 m.The basalts, andesites, and dacites are often highly porphyntic, containing phenocrysts of plagioclase and diopsidic augite, with olivine in the basic members and hypersthene and a titanomagnetite in the intermediate varieties. The rhyolite and rhyodacite lavas are weakly porphyritic and are characterized by phenocrysts of pyroxene, amphibole, biotite, and quartz. The groundmass of the basic lavas is often mostly glass, but when partly crystalline, it contains plagioclase, hypersthene, and/or pigeonite (usually the latter only), augite, iron-titanium oxides, and accessory tndymite or cristobalite.The Talasea basic lavas are quartz-normative, low in TiO2, and show moderate absolute iron-enrichment. The series has high K/Rb ratios and is low in K2O in comparison to other New Guinea lava series. Numerical evaluation of crystal fractionation of a possible basaltic parent shows that this process could account for all but the acid lavas of the Talasea series; it is only the dominance of andesite that suggests that the series was generated at a depth where andesite is the low melting composition. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Caldera

Stratovolcano

10.1130/0016-7606(1970)81[17:tvacot]2.0.co;2

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The volcanoes and caldera of Talasea, New Britain: Mineralogy

Contributions to Mineralogy and Petrology (1970)

Garry G. Lowder

Phenocryst

Andesites

Ilmenite

Fractional crystallization (geology)

Phlogopite

10.1007/bf00390081

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Citations (34)