[ { "id": "authors:gnwgg-w9778", "collection": "authors", "collection_id": "gnwgg-w9778", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131120-102238040", "type": "article", "title": "Archean mantle heterogeneity and the origin of diamondiferous eclogites, Siberia: Evidence from stable isotopes and hydroxyl in garnet", "author": [ { "family_name": "Snyder", "given_name": "Gregory A.", "clpid": "Snyder-G-A" }, { "family_name": "Taylor", "given_name": "Lawrence A.", "clpid": "Taylor-L-A" }, { "family_name": "Jerde", "given_name": "Eric A.", "clpid": "Jerde-E-A" }, { "family_name": "Clayton", "given_name": "Robert N.", "clpid": "Clayton-R-N" }, { "family_name": "Mayeda", "given_name": "Toshiko K.", "clpid": "Mayeda-Toshiko-K" }, { "family_name": "Deines", "given_name": "Peter", "clpid": "Deines-P" }, { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Sobolev", "given_name": "Nikolai V.", "clpid": "Sobolev-N-V" } ], "abstract": "Data are presented for the O isotopic composition of clinopyroxene and garnet, the C isotopic composition of diamond, and the OH- content of garnet from eclogite xenoliths brought to the surface by the Udachnaya kimberlite pipe, Yakutia, Siberia. Radiogenic isotopic data suggest that the eclogites could have been derived from an ultradepleted mantle at approximately 2.9 Ga (Pearson et al., 1995; Snyder et al., in preparation). O isotopic compositions generally show equilibration between the eclogitic minerals (\u0394_(cpx-Grt) = 0.11-0.41\u2030) and have \u03b4^(18)O_(SMOW) for both garnet and clinopyroxene that lie near the range of accepted mantle values of 5.7\u00b10.7\u2030. However, several eclogites indicate significant deviations from this range, at higher values of 6.8-7.0\u2030. Also, two eclogites lie at the lower end of the mantle range, at values of 4.8 and 5.0\u2030 (all in clinopyroxene). C isotopic compositions of diamonds all have \u03b4^(13)C_(PDB) in the range of -1 to -7\u2030 and are centered at approximately -5\u2030, also within the range of accepted mantle values. The\nOH- contents of the garnet are generally between 0 and 22 ppm (as H_(2)0), although two samples exceed 70 ppm. This range of OH- is similar to eclogitic garnet from the Kaapvaal craton of southern Africa. The mantle C isotopic values of associated diamonds, the majority of O isotopic data, and the low OH- content of the minerals, although suggesting a general lack of crustal participation in the formation of the Udachnaya eclogites, do not rule out the participation of some ancient crustal material. That these eclogites include both ^(18)O-enriched and ^(18)O-depleted types suggests that the protoliths may have been overprinted by both low- and high-temperature hydrothermal events (cf. Jacob et aI., 1994). A positive correlation between \u03b4^(18)O and ^(87)Sr/^(86)Sr allows the interpretation of these eclogites as representing a cross section of an Archean ophiolite. However, the lack of a single coherent grouping on a plot of \u03b4^(18)O vs. ^(87)Sr/^(86)Sr suggests that, if the Udachnaya eclogites were derived from oceanic crust, they cannot be cogenetic and must represent at least two separate ophiolite sequences. Conversely, if the eclogites are found to be cogenetic, then a totally different process affected their formation and a probable metasomatic mechanism was operative. Because of the total lack of correlation of \u03b4^(18)O with other geochemical parameters, we find no compelling evidence that all eclogites are derived ultimately from oceanic crust.", "issn": "0003-004X", "publisher": "Mineralogical Society of America", "publication": "American Mineralogist", "publication_date": "1995-07", "series_number": "7-8", "volume": "80", "issue": "7-8", "pages": "799-809" }, { "id": "authors:99zy0-r2696", "collection": "authors", "collection_id": "99zy0-r2696", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141008-113453669", "type": "article", "title": "Geochemistry of Precambrian carbonates: V. Late Paleoproterozoic seawater", "author": [ { "family_name": "Veizer", "given_name": "J\u00e1n", "clpid": "Veizer-J" }, { "family_name": "Plumb", "given_name": "K. A.", "clpid": "Plumb-K-A" }, { "family_name": "Clayton", "given_name": "R. N.", "clpid": "Clayton-R-N" }, { "family_name": "Hinton", "given_name": "R. W.", "clpid": "Hinton-R-W" }, { "family_name": "Grotzinger", "given_name": "J. P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" } ], "abstract": "In an effort to obtain better constrained data for the first- and second-order variations in the isotopic composition of late Paleoproterozoic (1.8 \u00b1 0.2 Ga) seawater, we report a study of mineralogy, chemistry, and isotopic composition of the Coronation Supergroup (~1.9 Ga, NWT), Canada, and the McArthur Group (~1.65 Ga, NT), Australia. Petrologically, both carbonate sequences are mostly dolostones. The McArthur population, however, contains more abundant textural features that attest to the former presence of sulfates and halite, and the facies investigated herein probably represent ancient equivalents of modern evaporitic sabkhas and lacustrine playa lakes. This is reflected in ^(18)O enrichment (up to \u22122.9%. PDB) and high Mn, Fe, and Sr concentrations. Nonetheless, the available \u0394^(18)O data indicate that the \"best estimate\" for the Archean to late Paleoproterozoic limestones is about \u22127%. PDB, with dolostones some 3 \u00b1 2%. heavier. The observed \u0394^(18)O_doiomitc-calcite is thus within the range of the proposed fractionation factor for a cogenetic mineral pair. This, together with the consistency of isotopic patterns for sedimentological facies over almost 2 billion years, from the late Paleoproterozoic to the present, suggest that dolomitization was an early diagenetic event and that the ^(18)O depletion of the Archean to late Paleoproterozoic carbonates is not an artefact ofpost-depositional alteration. The \u03b4^(13)C, although within the range of other Precambrian and Phanerozoic carbonates, indicates a possible secular evolution from 0 \u00b1 2%. PDB at 1.9 Ga ago to \u22121 \u00b1 1.5%. at 1.65 Ga ago. The secular evolution for reflects the ^(87)Sr increase from 0.7031 \u00b1 0.0008 at 3.5 \u00b1 0.1 Ga ago, through 0.7025 \u00b1 0.0015 at 2.8 \u00b1 0.2 Ga, 0.7033 at 2.5 Ga, 0.7050 at 2.25 \u00b1 0.25 Ga, 0.7047 at 1.91, to \u22640.706 at 1.65 Ga ago.", "doi": "10.1016/0016-7037(92)90204-V", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1992-06", "series_number": "6", "volume": "56", "issue": "6", "pages": "2487-2501" }, { "id": "authors:4km39-42292", "collection": "authors", "collection_id": "4km39-42292", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170427-090016157", "type": "article", "title": "Murchison xenoliths", "author": [ { "family_name": "Olsen", "given_name": "Edward J.", "clpid": "Olsen-E-J" }, { "family_name": "Davis", "given_name": "Andrew M.", "clpid": "Davis-A-M" }, { "family_name": "Hutcheon", "given_name": "Ian D.", "clpid": "Hutcheon-I-D" }, { "family_name": "Clayton", "given_name": "Robert N.", "clpid": "Clayton-R-N" }, { "family_name": "Mayeda", "given_name": "Toshiko K.", "clpid": "Mayeda-Toshiko-K" }, { "family_name": "Grossman", "given_name": "Lawrence", "clpid": "Grossman-L" } ], "abstract": "C3 xenoliths in a C2 host (Murchison) are unique among known meteoritic xenolith-host occurrences. They offer an opportunity to determine possible effects on the xenoliths by the hydrated host. Eleven xenoliths were found ranging from 2 to 13 mm. Four of these Murchison Xenoliths (MX1, MX2, MX3 and MX4) have been studied in detail. MX1 and MX2 were large enough for trace element, oxygen isotope, carbon isotope, bulk carbon and bulk nitrogen determinations. All four were studied petrographically and by analytical SEM. The xenoliths cannot be unequivocally identified as C3V or C3O subtypes. MX1 contains some matrix phyllosilicate, indicating reaction with water. MX 1, MX2 and MX3 all show extensive alteration by an FeO-rich medium, and some minerals in them contain ferric iron. MX4, however, exhibits very minor alteration by FeO only. Oxygen isotopic and chemical data show that the alteration of these xenoliths did not take place in the Murchison host. The alterations occurred in one or more parent bodies, which were later disrupted to release these xenoliths that ultimately accreted onto the Murchison parent body.", "doi": "10.1016/0016-7037(88)90230-X", "issn": "0016-7037", "publisher": "Elsevier", "publication": "Geochimica et Cosmochimica Acta", "publication_date": "1988-06", "series_number": "6", "volume": "52", "issue": "6", "pages": "1615-1626" } ]