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Cenozoic post-collision paleo lithospheric thinning of SE Kalimantan (Borneo), Indonesia: constraints from alkaline lamprophyre thermobarometry and geochemistry

Edafe Ominigbo1 , David Murphy1, Jessica Trofimovs1, Tim A. Moore1,2,3, Carmen Gaina4, Ferian Anggara5

  • Affiliations:  1School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Australia.   2Cipher Consulting Pty Ltd., Brisbane, Australia.   3School of Resources and Geoscience, China University of Mining and Technology, Xuzhou, China.    4Department of Geoscience, University of Oslo, Oslo, Norway.   5Department of Geological Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia. 

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 29

  • Programme No: 1.7.16

  • Theme 1 > Session 7

Abstract

Abstract Modern igneous petrology is founded on the combined observations of active magmatic systems, petrochemistry, experimental petrology and geothermobarometry. These disciplines allow reconstruction of past igneous systems and petrotectonic processes. Therefore, with relevant samples and appropriate analytical techniques, aspects of paleo-lithospheric structure at the time of magma eruption or intrusion can be inferred. The present-day lithosphere in Borneo, Southeast Asia, is very thin due to extensional tectonics associated with the opening of the Makassar Strait (Burton-Johnson & Cullen, 2023; Murphy et al., 2024). However, the actual mechanism(s) behind this inferred stretching remains poorly understood. Here, we investigate the petrogenesis and geothermobarometry of shallow alkaline, petrologically diverse mafic sills and dykes that intruded into Eocene sediments in southeast Kalimantan (Borneo), Indonesia with the aim of gaining insights into the magma plumbing system and Cenozoic paleo lithospheric architecture of the region. Rock samples, including alkaline (camptonite) lamprophyres and alkali olivine basalts from peninsular Senakin and Petangis in southeast Kalimantan were collected for this study. Whole rock geochemistry and in-situ analytical techniques will be used to constrain the P-T conditions the magma plumbing systems that fed the dykes and sills. Findings from the study will offer insights into the Eocene crustal thickness in southeast Kalimantan with implications for the thickness of the Cenozoic lithosphere prior to regional extension. Results will also enhance our understanding of the mechanism(s) driving the extensional tectono-volcanic evolution of the region.