Rock Magnetic, Petrography, and Geochemistry Studies of Lava at the Ijen Volcanic Complex (IVC), Banyuwangi, East Java, Indonesia

Abstract

Lava has complex geochemical characteristics based on differences in eruption centers, eruptive events, and flow emplacement. Characterization of lava is useful for understanding the geological conditions of a volcanic region. To complement geochemical methods, rock magnetic methods are being used to analyze lava. To explore the potential uses of rock magnetic methods for lava characterization, a series of magnetic measurements were completed in lava samples from eight locations in the Ijen Volcanic Complex (IVC) in Banyuwangi, East Java, Indonesia. These locations were grouped into two eruption centers: Ijen Crater and Mount Anyar. The magnetic measurements included frequency-dependent magnetic susceptibility, thermomagnetic, anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), and hysteresis curve analyses. These measurements were supplemented using X-ray fluorescence, petrography analyses, and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). Based on their lithology, lava samples were categorized into basalt, basaltic andesite, and basaltic trachyandesite. The dominant magnetic mineral contained in the sample was iron-rich titanomagnetite and titanium-rich titanomagnetite with a magnetic pseudo-single-domain and small amounts of superparamagnetic grain minerals in some samples. The significant difference in mass specific susceptibility (χ LF ) is caused by differences in the crystallization process. The differences in susceptibility frequency dependence (χ FD ) highlighted the differences in the magma cooling rate, demonstrated by the differences in the percentage of opaque mineral groundmass. The rock magnetic method was proven to support the geochemistry and petrography methods used to characterize lava and identify the causes of differences in lava characteristics.

Anisotropy of Magnetic Susceptibility and Preferred Pore Orientation in Lava Flow from the Ijen Volcanic Complex, East Java, Indonesia

“…We used five lava samples from five different outcrops in the Ijen Volcanic Complex, West Java, Indonesia (Figure 1), the outcrops of which have been the sites of previous research [24,25]. Identifying mineralogy, texture, geochemistry, and rock magnetic properties of lavas, which were resulted from Ijen Crater and Mount Anyar eruptions was performed in a previous study [25]. Four samples (ANY1, ANY2, ANY3, and ANY4) are products of Mount Anyar's eruption.…”

“…The eruptions occurred about 2590 years ago [26]. The characteristics of all samples (based on reference [25]) are shown in Table 1.…”

“…The Ijen Volcanic Complex map shows the distribution of volcanic products and eruption centers. Red dots indicate the sampling sites (modified from reference[25]). …”

Petrology and geochemistry dataset of lava from the Ijen Crater and Mount Blau, Banyuwangi, East Java, Indonesia

“…3), lava samples from the Ijen Crater could be classified into two lithologies: basaltic andesite and andesite, meanwhile, lava samples from Mount Blau had andesite lithology. As a comparison, we also plotted the lava samples data from the Ijen Crater that were used in the previous study [1]. Major elements contents of the Ijen Crater lava samples from Ref.…”

“…Measured trace elements are Ba, Cu, Zn, Rb, Sr, Co, Y, and V. Meanwhile, Mineralogy and rock texture analysis were done with the observation of the samples' thin section through a polarizing microscope.Data source locationInstitution: (1) Center for Geological Survey (CGS) of Indonesia, (2) Faculty of Earth Sciences and Technology, Institut Teknologi BandungCity: BandungProvince: West JavaCountry: IndonesiaSampling locations: Ijen Crater and Mount Blau, Ijen Volcanic ComplexCity: BanyuwangiProvince: East JavaCountry: IndonesiaData accessibilityThe data are available within this article.Related research articleAuthor's name: Aditya Pratama, Satria Bijaksana, Mirzam Abdurrachman, and Nono Agus SantosoTitle: Rock Magnetic, Petrography, and Geochemistry Studies of Lava at the Ijen Volcanic Complex (IVC), Banyuwangi, East Java, IndonesiaJournal: Geosciences 2018, 8, 183https://doi.org/10.3390/geosciences8050183…”