Petrology and crustal inheritance of the Cloudy Bay Volcanics as derived from a fluvial conglomerate, Papuan Peninsula (Papua New Guinea): an example of geological inquiry in the absence of in situ outcrop

Holm, Robert, and Poke, Benny (2018) Petrology and crustal inheritance of the Cloudy Bay Volcanics as derived from a fluvial conglomerate, Papuan Peninsula (Papua New Guinea): an example of geological inquiry in the absence of in situ outcrop. Cogent Geoscience, 4 (1). 1450198.

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Abstract

In regions of enhanced weathering and erosion, such as Papua New Guinea, our ability to examine a complete geological record can become compromised by the absence of in situ outcrops. In this study, we provide an example of the insights that can be gained from investigations of secondary deposits. We sampled matrix material and clasts derived from an isolated conglomerate outcrop within a landscape dominated by lowland tropical forest of the southeast Papuan Peninsula, and mapped as belonging to the Cloudy Bay Volcanics. Nine variations of volcanic rock types were identified that range from basalts to trachyandesites. Major and trace element geochemistry characterize the volcanic arc assemblage as shoshonites and provide evidence for differential magma evolution pathways with a subset of samples marked by heavy REE- and Y-depletion, indicative of high-pressure magma fractionation. Zircon U–Pb dating of the individual volcanic clasts indicates activity of the Cloudy Bay Volcanics was largely constrained to the latest Miocene, between ca. 7 and 5 Ma. Of the analyzed zircons, the majority are xenocrystic zircons that provide insight into the provenance of the Papuan Peninsula with potentially significant implications for South West Pacific tectonics. Additional Hf-isotope analysis of the primary igneous zircons suggests a relatively unradiogenic crustal component contributed to magma compositions, which cannot be readily explained by current regional tectonic paradigms.

Item ID: 53095
Item Type: Article (Research - C1)
ISSN: 2331-2041
Keywords: Papua New Guinea; volcanic; conglomerate; shoshonite; U-Pb geochronology; zircon provenance; Hf isotope
Additional Information:

This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license

Funders: Australian Geoscience Council (AGC), Australian Academy of Science (AAS), James Cook University (JCU)
Projects and Grants: AGC and AAS 34th International Geological Congress Travel grant Scheme for Early-Career Australian and New Zealand Geoscientists, JCU Early Career Researcher Rising Stars Leadership Program Grant
Date Deposited: 11 Apr 2018 04:38
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040304 Igneous and Metamorphic Petrology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040303 Geochronology @ 30%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040699 Physical Geography and Environmental Geoscience not elsewhere classified @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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