Noble gas isotopic composition and abundances were determined on dry gas sampled in geothermal wells from the Bacon-Manito (BGPF) geothermal field in the Philippines. The most significant findings come from the (3)He/(4)He ratio; a mantle-He source is evidenced by ratio close to 7 Ra. Peripheral fluid from the west and south of the geothermal system is relatively enriched in (4)He (R/Ra slightly > 2), most probably sourced from U and Th decay in old igneous or crustal rocks. The two end-members mix, producing the range of R/Ra ratios observed in the other wells included in this study. Preliminary data on the delta(11)B signature of the Bacon Manito fluid separated from vapour range from 7 parts per thousand to 9 parts per thousand. These values suggest that the local magmatic rocks could represent the main boron source, in agreement with the boron isotopic signature of Pacific arc lavas.
Noble gas and boron isotopic signatures of the Bacon-Manito geothermal fluid, Philippines.
Magro G;Pennisi M
2008
Abstract
Noble gas isotopic composition and abundances were determined on dry gas sampled in geothermal wells from the Bacon-Manito (BGPF) geothermal field in the Philippines. The most significant findings come from the (3)He/(4)He ratio; a mantle-He source is evidenced by ratio close to 7 Ra. Peripheral fluid from the west and south of the geothermal system is relatively enriched in (4)He (R/Ra slightly > 2), most probably sourced from U and Th decay in old igneous or crustal rocks. The two end-members mix, producing the range of R/Ra ratios observed in the other wells included in this study. Preliminary data on the delta(11)B signature of the Bacon Manito fluid separated from vapour range from 7 parts per thousand to 9 parts per thousand. These values suggest that the local magmatic rocks could represent the main boron source, in agreement with the boron isotopic signature of Pacific arc lavas.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
