Novel Amphibole Geo-barometer with Application to Mafic Xenoliths

Abstract

Amphibole crystallization from hydrous high-magnesium andesite (Shiveluch volcano, Kamchatka) melt has been studied experimentally at pressures 2, 3, 5 kbar. Slightly subliquidus temperatures have been selected for amphibole crystallization. Amphiboles with close to the equilibrium composition have been obtained at low undercoolings in short 4 hours experiments. We select octahedral aluminium content and sum of high charged cations (Ti 4+ , Fe 3+ ) all evaluated with the 13eCNK method as master parameters reflecting pressure of amphibole formation. Asymptotic maximum of Al VI content at the sum Ti+Fe 3+ =0 as a function of pressure was calculated following negative linear correlation trend for each run of the original and published experimental data sets. The derived novel Al VI in amphibole barometer is calibrated in the pressure range of 2-12 kbar for andesitic and basaltic magmas. Reliability and validity of the new geobarometer were tested on the amphibolized ultramafic xenoliths from the Shiveluch Volcano (Kamchatka) and Dish Hill (California). In both cases our estimates appear to be equal within the uncertainty of the method to the predictions done by two-pyroxene geo-thermo-barometer (Putirka, 2008).

Amphibole perspective to unravel pre-eruptive processes and conditions in volcanic plumbing systems beneath intermediate arc volcanoes: a case study from Ciomadul volcano (SE Carpathians)

“…St. Helens dacites, where a vertically elongated, 757 large magma chamber is hypothesized (Pallister et al 758 2008). However, no such simple-zoned and composite Simakin et al (2012) 775 primitive (i.e., near liquidus) amphiboles is related to the 776 P H2O , and therefore, their hygro-barometer can be used for 777 the pargasites. Although we do not have direct evidence of 778 H 2 O saturation in the Ciomadul magmas, the lack of neg-779 ative Eu anomaly in the pargasites probably suggests that 780 they are originated from a melt that was too H2O-rich to 781 crystallize plagioclase.…”

Petrological Characteristics of the Satkatbong Pluton, Yeongdeok, Korea

“…Al content in the margin of amphibole grain (Al T ) is proportional to the emplacement depth (Spear, 1981;Schmidt, 1992;Simakin et al, 2012). When comparing total aluminum (Al T ) with tetrahedral aluminum (Al i v ) plotted on the graph (Leake, 1971), Al T of the Satkatbong pluton is relatively lower than those of the others through a degree of slopes of each pluton (Fig.…”

Petrological characteristics of the Yeongdeok granite

“…8) 철 이온의 산화상태를 점시한 그래프 (Hine et al, 1978)에서는 대체적으로 2가철과 3가철의 비가 1:1에 가깝게 분포하여 I-형 화 강암류의 특징을 나타내었다 (Fig. 9) (Spear, 1981;Simakin et al, 2012). 이 근거로부터 경험적, 실험적으로 파 생된 여러 각섬석 지압계들 (Hammarstrom and Zen, 1986;Hollister et al, 1987;Johnson and Rutherford, 1989;Schmidt, 1992 …”