Stanford Geothermal WorkshopFebruary 12-14, 2018

Deducing Geothermal Upflow Zone from Rare Earth Elements at Early-Stage Geothermal Exploration Riostantieka Mayandari SHOEDARTO, Yohei TADA, Koki KASHIWAYA, Taiki KUBO, Katsuaki KOIKE, Irwan ISKANDAR, M. Nur HERIAWAN, Sudarto NOTOSISWOYO, Dwiyogarani MALIK [Kyoto University, Japan]

An integration of REEs analysis of oxygen and deuterium and normalized-to-host rocks REEs series from 8 acidic hot spring waters were investigated. The REEs concentrations in both types of sulfate and bicarbonate water introduced large variations with 3σ of BGD, with some undetected values. The varying distribution patterns in the light REEs presumably resulted from either due to shorter water-rock interaction times, which refers to dilution with meteoric water, or the presence of boiling zone. Two distinctive sulfate hot springs came up as the signature representatives of boiling zones in geothermal system. Boiling zones were predicted from hot spring with positive Eu anomaly and enriched oxygen isotope. Meanwhile, positive Ce anomaly could lead us to the hint of fully developed stage of water-rock interaction process in a geothermal system. Reversely, negative Ce anomaly gives a prediction of mixing geothermal fluid with surface water. Analyses of the REEs integrated with isotopes and chemistry analyses can provide an assistance to support geochemistry approaches for determining geothermal flow path analysis and boiling zones in a preliminary stage of geothermal exploration.

Topic: Geochemistry