Geochemical and magnetic properties of early pleistocene eruptions in Sangiran area, Central Java Province, Indonesia
1Shandiyano Putra, 1Aqilla Alya Pramita 1Budi Legowo, 2Agus Tri Hascaryo, 3Wiwit Suryanto, 1Budi Purnama*

1 Department of Physics, Sebelas Maret University, Jawa Tengah 57126, Indonesia
2Departement of Environment, Faculty of Civil and Planning Technology, Islamic Indonesia University, Yogyakarta, 55584, Indonesia.
3 Physics Department, Gadjah Mada University, Bulaksumur, BLS21, Yogyakarta, 55281, Indonesia

Abstract

This study aimed to identify the types of minerals and magnetic properties of an outcrop located in Sangiran. Sangiran is a primordial man archeological sites located between three volcanoes namely Merapi, Merbabu, and Lawu Volcano. Sangiran is known as an ancient site that holds fossils dating back thousands to millions of years. However, aside from that, there is a fact that steals the attention, namely the discovery of outcrops of that holds the results of ancient eruptions. We used the rock magnetism method. From the 27 samples we found, we took six samples that were representative of all the samples we found. To address these inquiries, a comprehensive investigation was conducted characterization test using X-Ray Fluoresence (XRF), X-Ray Diffractometer (XRD), and Vibrating Sample Magnetometer (VSM). The output of XRF characterization said that the sample were dominated by Si-O and Fe-O is element released during the process of eruptions. The XRD output showed minerals are magnetite, hematite, and greigite and the nonmagnetic minerals are calsilite, afwillite, quartz, and anorthite. The most intriguing aspect of this occurrence is the presence of greigite, a mineral that serves as a compelling evidence for the existence of a direct correlation between Sangiran, volcanic eruptions, and the presence of ancient humans in the region. Based on the output of VSM characterization test, each sample belongs to a soft magnet with a multidomain category.

Keywords: Rock Magnetic, Greigite, Soft Magnetic, Multi Domain

Topic: Earth Physics and Space Science