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Marinova, Margarita M.,Mckay, Christopher P.,Pollard, Wayne H.,Heldmann, Jennifer L.,Davila, Alfonso F.,Andersen, Dale T.,Jackson, W. Andrew,Lacelle, Denis,Paulsen, Gale,Zacny, Kris Cambridge University Press 2013 Antarctic science Vol.25 No.4
<B>Abstract</B><P>We report on 475 measurements of depth to ice-cemented ground in four high-elevation valleys of the Quartermain Mountains, McMurdo Dry Valleys, Antarctica. These valleys have pervasive ice-cemented ground, and the depth to ice-cemented ground and the ice composition may be indicators of climate change. In University Valley, the measured depth to ice-cemented ground ranges from 0-98 cm. There is an overall trend of increasing depth to ice-cemented ground with distance from a small glacier at the head of the valley, with a slope of 32 cm depth per kilometre along the valley floor. For Farnell Valley, the depth to ice-cemented ground is roughly constant (<I>c.</I> 30 cm) in the upper and central parts of the valley, but increases sharply as the valley descends into Beacon Valley. The two valleys north of University Valley also have extensive ice-cemented ground, with depths of 20-40 cm, but exhibit no clear patterns of ice depth with location. For all valleys there is a tendency for the variability in depth to ice-cemented ground at a site to increase with increasing depth to ice. Snow recurrence, solar insolation, and surface albedo may all be factors that cause site to site variations in these valleys.</P>
Kim, Nak Kyu,Choi, Sung Hi,Dale, Christopher W. Elsevier 2016 Lithos Vol.246 No.-
<P><B>Abstract</B></P> <P>We report combined Re–Os isotope and highly siderophile element data for whole-rock and whole-sulfide grains from Spitsbergen peridotites. The Os–Ir contents in whole-rocks are elevated compared to those of the primitive mantle, but the Pt–Pd–Re contents are depleted, reflecting refractory monosulfide solid solution (Mss) control during mantle melting. There are two general types of sulfide documented in global mantle samples: primary residual Mss with subchondritic Pd/Ir ratios and secondary metasomatic sulfides with suprachondritic Pd/Ir ratios. Most Spitsbergen sulfides have elevated Ir contents, and belong to the residual group. Most but not all Spitsbergen sulfides, however, are unusual in that they show a fractionation of Os (and Ru) from Ir which cannot be reconciled with a simple partial melting process. The Os(+Ru) fractionation from Ir is most notable in a sample containing mantle-derived carbonate-bearing pockets. Infiltration of carbonate-rich S-undersaturated melt into the Spitsbergen lithospheric mantle may result in the formation of localized S-rich liquid by dissolving residual Mss. Such melt compositions may promote laurite crystallization before Mss, causing the combined depletion of Os+Ru relative to Ir in later-formed Mss. The Re-depletion model ages of residual sulfide grains from Spitsbergen peridotites coincide with crustal ages determined for Spitsbergen, indicating coupled mantle–crust evolution, and furthermore, they coincide with the previously proposed major peaks of pulsed crustal formation periods in Earth at ca. 2.7, 1.9 and 1.2Ga.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report Re–Os isotope and PGE data for whole-sulfides from Spitsbergen peridotites. </LI> <LI> Combined Re–Os isotope and PGE systematics can be used for selecting a residual Mss. </LI> <LI> Laurite crystallization before Mss results in Os(+Ru) fractionation from Ir in sulfide. </LI> <LI> T<SUB>RD</SUB> ages of residual sulfides coincide with pulsed crustal formation periods in Earth. </LI> </UL> </P>