REE content of volcanic rocks and their weathered horizons in the Muria Volcanic Complex, Central Java, Indonesia

Sutarto, Sutarto and Sulaksono, Adi and Laksana, Dema T. and Mahyudani, Anggita and Setiahadiwibowo, Ajimas P and Nurcholis, Muhammad REE content of volcanic rocks and their weathered horizons in the Muria Volcanic Complex, Central Java, Indonesia. Bull Mineral Petrolog, 30 (1). pp. 28-37. ISSN 2570-7337

Text B.1.a.1. REE Content Of Volcanic Rocks And Their Weathered Horizons In The Muria Volcanic Complex_paper.pdf Download (857kB)

Abstract

We investigated bedrock samples and their weathered horizons collected from the Muria Volcanic Complex (MVC),
Central Java, Indonesia. In addition to petrographic study, samples were analysed using X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and inductively coupled plasma-mass spectrometry
(ICP-MS) for mineral composition, major elements, and trace elements, respectively. Bedrock samples (n = 10) from
the MVC have ΣREE ranging from 364 to 739 ppm (avg. 579 ppm). Basanite (n = 2) and phonotephrite (n = 2) are
consistently high in ΣREE (659 - 739 ppm) compared with basaltic trachyandesite, trachyandesite, and trachyte. Apatite is the only REE-bearing mineral observed in basanite and phonotephrite (up to ~1 vol.%). The ΣREE is positively
corelated with P2
O5
, which inversely corelates with SiO2
. The weathered horizons contain clay minerals that consist
primarily of kaolinite ± halloysite. The REE content of the weathered horizons (n = 7) is up to 183 ppm higher than those
of the bedrocks. The decrease in CaO and P2
O5 indicates a fractionation of apatite at early stage of magma evolution,
resulting in the depletion in the ΣREE content in the residual melt. We suggest that apatite is the major host of REE in
the MVC alkali-rich, silica-undersaturated volcanic rocks, as evidenced by our petrographic and geochemical data. We
also suggest that the increase in ΣREE in the weathered horizon is due to the presence of clay minerals, particularly
kaolinite and halloysite.
Keywords: apatite, REE, volcanic rocks, weathered horizons, clay minerals

Item Type:	Article
Uncontrolled Keywords:	apatite, REE, volcanic rocks, weathered horizons, clay minerals
Subjects:	Q Science > QE Geology
Divisions:	Faculty of Engineering, Science and Mathematics > School of Engineering Sciences
Depositing User:	Ir., MT SITI UMIYATUN CHOIRIAH
Date Deposited:	20 Mar 2023 01:31
Last Modified:	20 Mar 2023 02:34
URI:	http://eprints.upnyk.ac.id/id/eprint/32886

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