Multimethod Approach to the Study of Recent Volcanic Ashes from Tengger Volcanic Complex, Eastern Java, Indonesia

Abstract

Volcanic ash is a volcanic product with a wide distribution that can be used as a geological marker. In volcanic regions such as Indonesia, the identification of the sources of volcanic ash and tuff layers from different volcanoes or eruptive events is a challenging task. In this study, samples of volcanic ash from the 2010 eruption of Bromo-a relatively young and active tuff cone volcano within the Sandsea caldera in the Tengger volcanic complex in East Java, Indonesia-along with two older tuff layers from the same caldera (Widodaren tuff: 1.8 kyr and Segarawedi tuff: 33 kyr) were subjected to magnetic measurements, geochemical analyses, and petrographic analyses. The aim is to attempt to use magnetic characters as a fingerprint for volcanic ash and tuff layers. The results show that the samples had variations in grain size and magnetic domain as indicated by the hysteresis parameters. These magnetic characters correlated with the results of geochemical and petrographic analyses, suggesting that magnetic properties may potentially be used as fingerprints to identify volcanic ashes and tuff layers.

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

“…The presence of magnetite mineral (Fe-rich titanomagnetite) in the samples is supported by the high Tc (472-544 • C), whereas the presence of Ti-rich titanomagnetite is supported by the low Tc (<400 • C) [41]. This result can be caused by the temperature variation [31]. Figure 4b shows the ARM decay curve of IJ 1 and ANY 2.…”

“…All measurements were performed using the tools and steps previously described [31]. The parameters obtained from susceptibility measurements were χ LF , χ HF , and χ FD [31]. ARM measurements produced ARM decay curves that show the Median Destructive Field (MDF) value.…”

“…Each cube-shaped sample was inserted into a cylindrical plastic holder with a diameter of 25.4 mm, a height of 22 mm, and a volume of 10 cm 3 . All measurements were performed using the tools and steps previously described [31]. The parameters obtained from susceptibility measurements were χ LF , χ HF , and χ FD [31].…”

Identification of magnetic coercivity components in natural substances using Max Unmix web-application

“…For instance, in the case of volcanic ashes, the recent Bromo ash is clearly distinguishable from its older counterparts (Widodaren of 1.8 kyr and Segorowedi of 33 kyr). See [7] for details of the volcanic ashes. Similar analyses could be drawn for other samples.…”

Geochemical study to determine what elements are most influential in soil fertility in the southern part of Lampung region

“…Meanwhile, the South Lampung area around ITERA has the Lampung Formation which consists of pumice tuff, rhyolitic tuff, tuff solid tuff, tuffaceous mudstone and tuffaceous sandstone. The tuff on Mount Betung is blackish grey which indicates a lot of iron content [5,6,7]. Meanwhile, ITERA tuff is white which indicates a lot of silica content [8].…”