A comparison of olivine-melt thermometers based onDMgandDNi: The effects of melt composition, temperature, and pressure with applications to MORBs and hydrous arc basalts

Pu, Xiaofei; Lange, Rense; Moore, Gordon

doi:10.2138/am-2017-5879

Cited by 34 publications

(58 citation statements)

References 94 publications

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“…As expected, the BP basalts have D Ca ol/liq values in between those for the MORBs and arc basalts, consistent with melt water contents higher than those for mid-ocean ridge basalts, yet lower than those for active arc basalts. Thus, the D Ca ol/liq values in Figure 16 provide independent corroboration that the application of both the Mg and Ni thermometers from Pu et al (2017) to basalts (with olivine compositions that pass the Fe 2 þ -Mg K D liquidus test) provides accurate constraints on temperature and melt water contents at the onset of olivine crystallization.…”

Section: /2020gc009264mentioning

confidence: 60%

“…Because this approach only requires microprobe analyses of olivine analyses in thin sections (and whole-rock major-element and Ni contents), it can readily be applied to obtain large global data sets. To date, this approach has been verified for basalts from the BP volcanic field (this study) and the Tancítaro volcanic field in the Mexican arc (Pu et al, 2017). The ready attainment of large global data sets will allow the question of whether there are distinctly different temperatures and water contents in basalts erupted within and between different tectonic settings to be more fully addressed.…”

Section: Implications and Conclusionmentioning

confidence: 73%

“…Calculated temperatures using both the Mg and Ni thermometers are thus maximum values, and ΔT (=T Mg − T Ni ) is a minimum estimate. Pu et al (2017) calculate that a decrease in Fo by 1 mol% results in ΔT values that are 13-46°C too low for their samples. Again, because D Ni ol/liq is insensitive to dissolved water and variations in crustal pressure (Pu, 2018), T Ni values give the actual temperature at the onset of olivine growth.…”

Section: /2020gc009264mentioning

confidence: 98%

“…It has been proposed in the literature (e.g., Gavrilenko et al, 2016) that D Ca ol/liq values are a function of dissolved water content, with a potential to be used as an olivine-melt hygrometer. Here, a comparison is made between the average ΔT (=T Mg − T Ni ) values, obtained from the Pu et al (2017) thermometers, and the average D Ca ol/liq values obtained for three sets of basalts: (1) the BP basalts from this study, (2) Mexican arc basalts (Pu et al, 2017), and (3) the suite of mid-ocean ridge basalts (Allan et al, 1989) examined in Pu et al (2017). The data are plotted in Figure 16 and reveal a strong inverse, Pu et al, 2017), (2) mid-ocean ridge basalts (Allan et al, 1989;Pu et al, 2017), and (3) BP basalts from this study.…”

Section: Correlation Between D Ca Ol/liq and Depression Of Olivine Limentioning

confidence: 99%

“…The K D values from MELTS do not vary with oxidation state between ΔQFM = −1 to +1, and the value at ΔNNO = 0 is reported inTable 2. For the Putirka (2016) model, the effect of pressure on the K D value is negligible at crustal depths Pu et al (2017). showed that~5-6 wt% dissolved H 2 O leads to an increase in Fe 2 þ -Mg K D (olivine-melt) value by ≤0.03, and thus, a small increase in K D…”

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confidence: 99%

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Evidence of Rapid Phenocryst Growth of Olivine During Ascent in Basalts From the Big Pine Volcanic Field: Application of Olivine‐Melt Thermometry and Hygrometry at the Liquidus

Brehm

Lange

2020

Geochem Geophys Geosyst

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The Quaternary Big Pine (BP) volcanic field in eastern California is notable for the occurrence of mantle xenoliths in several flows. This points to rapid ascent of basalt through the crust and precludes prolonged storage in a crustal reservoir. In this study, the hypothesis of phenocryst growth during ascent is tested for several basalts (13-7 wt% MgO) and shown to be viable. Phenocrysts of olivine and clinopyroxene frequently display diffusion-limited growth textures, and clinopyroxene compositions are consistent with polybaric crystallization. When the most Mg-rich olivine in each sample is paired with the whole-rock composition, resulting Fe 2 þ-Mg K D (olivine-melt) values (0.31-0.36) match those calculated from literature models (0.32-0.36). Application of a Mg-and a Ni-based olivine-melt thermometer from the literature, both calibrated on the same experimental data set, leads to two sets of temperatures that vary linearly with whole-rock MgO wt%. Because the Ni thermometer is independent of water content, it provides the actual temperature at the onset of olivine crystallization (1247-1097°C), whereas the Mg thermometer gives the temperature under anhydrous conditions and thus allows ΔT (=T Mg − T Ni = depression of liquidus due to water) to be obtained. The average ΔT for all samples is~59°C, which is consistent with analyzed water contents of 1.5-3.0 wt% in olivine-hosted melt inclusions from the literature. Because the application of olivine-melt thermometry/hygrometry at the liquidus only requires microprobe analyses of olivine combined with whole-rock compositions, it can be used to obtain large global data sets of the temperature and water contents of basalts from different tectonic settings. Plain Language Summary Basaltic lavas are a window into their mantle source regions, which is why it is important to determine their temperatures and water contents. In this study, a new approach that allows these two parameters to be quantified is demonstrated for basalts from the Big Pine volcanic field, CA. They were targeted because many contain chunks of dense mantle rocks, which precludes storage in a crustal magma chamber and points to direct ascent from the mantle to the surface along fractures. Two hypotheses are proposed, tested, and shown to be viable in this study: (1) olivine crystallized in the basalts during ascent, and (2) the most Mg-rich olivine analyzed in each basalt represents the first olivine to grow during ascent. This enables the most Mg-rich olivine to be paired with the whole-rock composition in the application of olivine-melt thermometry and hygrometry. The results match those from published, independent studies. The success of this approach paves the way for the attainment of large, high-quality data sets for basalts from a wide variety of tectonic settings. This, in turn, may allow global variations in mantle temperature and volatile content to be mapped in greater detail and better understood.

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Section: /2020gc009264mentioning

confidence: 60%

Section: Implications and Conclusionmentioning

confidence: 73%

Section: /2020gc009264mentioning

confidence: 98%