Determination of Scandium in mafic and ultramafic rocks of ophiolites from Luk Ulo Complex, Karangsambung, Central Java, Indonesia

摘要

Scandium (Sc) is important element for its utilization in modern industry. Initial Sc content in the parent rocks primary importance controlling the Sc concentrations in its weathered derivatives. This contribution examines the Sc concentrations in parent rocks of mafic and ultramafic rocks related to the ophiolite series in Luk Ulo Complex, Karangsambung, Central Java, Indonesia. The ophiolite series in this area are basalt, microgabbronorite, gabbronorite, websterite, and serpentinite from 5 locations of Medana, Lokidang, Parakansubah, Selogiri, and Pucangan areas. The general trend from the distribution of Sc in the ophiolite sequence of Medana and Parakansubah-Lokidang Rivers suggests the Sc contents increase from shallow to deeper levels of the sequence. The lowest concentrations of Sc in the ophiolite sequence of Medana and Parakansubah-Lokidang Rivers are in basalt, which are 24–29 ppm. In the middle sequence, the Sc concentrations are 27–34 ppm and 24–43 ppm, respectively in microgabbronorite and gabbronorite. The highest Sc concentrations are in websterite, which are 51–54 ppm, as the deepest sequence of the ophiolite in this area. Meanwhile, Sc contents in serpentinite from Selogiri and Pucangan areas are 5–11 ppm, which are considered the lowest Sc contents. It suggests that the pre-serpentinization mineral composition rather than the process of serpentinization determine the elemental abundance of Sc in serpentinite. The results are used to be an analog for Sc identification in the ophiolite belts in central Indonesia. This also considering that Luk Ulo Complex been established as National Geopark of Karangsambung-Karangbolong, so that mining activities are prohibited in this area.