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

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.