Noble gases in diamonds: Occurrences of solarlike helium and neon

Honda, Masahiko; Reynolds, J. H.; Roedder, Edwin; Epstein, Samuel

doi:10.1029/jb092ib12p12507

Cited by 91 publications

(19 citation statements)

References 37 publications

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“…It is more akin to solar Ne. This important conclusion is now well established from recent precise Ne isotopic analyses on MORB (Sarda et al 1988, Marty 1989, Honda et al 1991, Hiyagon et al 1992) and on diamonds (Honda et al 1987, Ozima and Zashu 1988, 1991. The fact that the dissimilarity of the isotopic composition between the mantle and air is only seen in Ne supports the hypothesis Except for 78Kr, which is rare and therefore its measurement is very uncertain, mantle Kr is indistinguishable from atmospheric Kr.…”

Section: Noble Gas Constraintssupporting

confidence: 60%

Mantle degassing and atmospheric evolution: Noble gas view.

Ozima

Zahnle

1993

Geochem. J.

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Section: Noble Gas Constraintssupporting

confidence: 60%

Mantle degassing and atmospheric evolution: Noble gas view.

Ozima

Zahnle

1993

Geochem. J.

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“…Gases interpreted to be from a primitive source in the Hawaiian islands also have values of -3.6 to -3.0%0 ( GERLACH and THOMAS, 1986). Recent work has suggested that a positive correlation may exist between 3He/4He and 6 r3C, with the heavier carbon isotopic composition being typical of primordial sources (HONDA et al, 1987). +,,, of the calcite is 0 to +2, similar to that for the silicate portion of the rock (Fig.…”

Section: Isotopic Composition Of the Calcite Segregationsmentioning

confidence: 66%

An unusual mantle source region for nephelinites from the Oslo Rift, Norway

Anthony

Segalstad

Neumann

1989

Geochimica et Cosmochimica Acta

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Abstract-Wehave analyzed the trace-element and isotopic composition of a series of lavas and their constituent pyroxenes and calcite from near the town of Skien in the Permo-Carboniferous Oslo Rift. The series decreases in alkalinity upsection: the lowermost layaS are n~heli~t~, followed by basanites and finally alkali basalts. This sequence is accompanied by decreasing light ram earth element (LREE), Th, Nb and U concentrations. Nd isotopic change is strongly correlated with the petrologic and chemical evolution. The nephelinites are characterized by cNd (300 Ma) of 1.0 to 1.6, the basanites 1.9 to 2.2 and the alkali basalts 2.4 to 3.9. cSr (300 Ma) ranges from -10 to -15 and shows little change from one group to the next. Calcite segregations in the basaltic rocks show 6'-'C = -2.825, 6'*0 = 7.7 to 9.6%, tsr = -6.5 to -9.9 and Q.+, = 0 to +2, values which are compatible with formation from magmatic CO, exsolved from a mantle-derived silicate melt.The Sr isotope values are unradiogenic relative to Nd for the nephelinites, causing these samples to fall to the lefthand side of most rn~tl~~y~ rocks on a eNd vs. 6sr diagram. They are similar to rocks from "high p" (HIMU) sources and the recently proposed "LoNd array" f HART et al., 1986). The alkali basal&, with their higher cNd, lie close to the mantle array for 300 Ma ago and resemble tholeiitic magmatism in the Oslo Rift. We interpret these trends as representing evolution in which the earliest magmas were derived from a source with HIMU-LoNd characteristics, and successive magmas gradually acquired the more dominant mantle isotopic composition. Model age calculations permit either 1) that the nephelinite source was originally depleted then subsequently re-enriched in LREE or 2) that the nephelinite source was primitive with respect to Nd but had undergone Rb depletion. The nearby Fen carbonatite complex is about 250 Ma older than Skien and its em is slightly more positive. A direct ~~tion~ip between Fen and Skien would favor the first hypothesis.

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“…Assuming an upper limit given by the ReOs age of 3.52 Ga for peridotitic diamonds (Westerlund et al, 2006), although incompatible with N aggregation data, gives in situ produced 4 He concentrations higher than those measured in all the samples except for PEK013/4 where it would account for 41% of the total 4 He. At present it is not possible to determine whether the diamonds have quantitatively retained He (young coats) or experienced He loss by diffusion (ancient coats) although negligible He loss is most likely for diamond (Honda et al, 1987). From hereon, it is assumed that no major addition or loss of He has occurred, and that the He abundances and isotope ratios are representative of the fluid trapped at the time of coat crystallisation.…”

Section: Helium and Argon Isotopesmentioning

confidence: 97%