Chemical Evolution of the Igneous Rocks of the Eastern West Indies: An Investigation of Thorium, Uranium, and Potassium Distributions, and Lead and Strontium Isotopic Ratios

1971 ◽  
pp. 181-224 ◽  
Author(s):  
Thomas W. Donnelly ◽  
John J. W. Rogers ◽  
Paul Pushkar ◽  
Richard Lee Armstrong
Keyword(s):  
Chemical Evolution ◽  
West Indies ◽  
Igneous Rocks ◽  
Isotopic Ratios

scholarly journals The chemical connection between 67P/C-G and IRAS 16293-2422

2017 ◽  
Vol 13 (S332) ◽  
pp. 196-201
Author(s):  
Maria Nikolayevna Drozdovskaya ◽  
Ewine F. van Dishoeck ◽  
Martin Rubin ◽  
Jes Kristian Jørgensen ◽  
Kathrin Altwegg
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
Chemical Evolution ◽  
Protoplanetary Disks ◽  
In Situ Measurements ◽  
Isotopic Ratios ◽  
Data Sets ◽  
Low Mass ◽  
Comet 67P

AbstractThe chemical evolution of a star- and planet-forming system begins in the prestellar phase and proceeds across the subsequent evolutionary phases. The chemical trail from cores to protoplanetary disks to planetary embryos can be studied by comparing distant young protostars and comets in our Solar System. One particularly chemically rich system that is thought to be analogous to our own is the low-mass IRAS 16293-2422. ALMA-PILS observations have made the study of chemistry on the disk scales (<100 AU) of this system possible. Under the assumption that comets are pristine tracers of the outer parts of the innate protosolar disk, it is possible to compare the composition of our infant Solar System to that of IRAS 16293-2422. The Rosetta mission has yielded a wealth of unique in situ measurements on comet 67P/C-G, making it the best probe to date. Herein, the initial comparisons in terms of the chemical composition and isotopic ratios are summarized. Much work is still to be carried out in the future as the analysis of both of these data sets is still ongoing.

scholarly journals Calcium isotopic evidence for the mantle sources of carbonatites

2020 ◽  
Vol 6 (23) ◽  
pp. eaba3269 ◽  
Author(s):  
Elsa Amsellem ◽  
Frédéric Moynier ◽  
Hervé Bertrand ◽  
Amaury Bouyon ◽  
João Mata ◽  
...  
Keyword(s):  
Mantle Source ◽  
Igneous Rocks ◽  
Isotopic Ratios ◽  
Carbonate Minerals ◽  
Isotopic Evidence ◽  
Calcium Isotopes ◽  
Mantle Sources ◽  
Marine Carbonates ◽  
Carbonate Materials ◽  
Silicate Rocks

The origin of carbonatites—igneous rocks with more than 50% of carbonate minerals—and whether they originate from a primary mantle source or from recycling of surface materials are still debated. Calcium isotopes have the potential to resolve the origin of carbonatites, since marine carbonates are enriched in the lighter isotopes of Ca compared to the mantle. Here, we report the Ca isotopic compositions for 74 carbonatites and associated silicate rocks from continental and oceanic settings, spanning from 3 billion years ago to the present day, together with O and C isotopic ratios for 37 samples. Calcium-, Mg-, and Fe-rich carbonatites have isotopically lighter Ca than mantle-derived rocks such as basalts and fall within the range of isotopically light Ca from ancient marine carbonates. This signature reflects the composition of the source, which is isotopically light and is consistent with recycling of surface carbonate materials into the mantle.

A study of the isotopic abundance of boron from various sources

1968 ◽  
Vol 5 (4) ◽  
pp. 921-927 ◽  
Author(s):  
E. K. Agyei ◽  
C. C. McMullen
Keyword(s):  
Boric Acid ◽  
Atomic Weight ◽  
Igneous Rocks ◽  
Tokyo Bay ◽  
Standard Errors ◽  
Isotopic Ratios ◽  
Isotopic Abundance ◽  
A Value ◽  
The Mean ◽  
The Absolute

The absolute ratio of 11B/10B has been determined for boron from different terrestrial sources with a precision of 0.2% (two standard errors) and a reproducibility of 0.2% (half-range). Values fall in the range 4.108 to 3.987 (i.e. 3% variation) and give a corresponding range in the boron atomic weight of 10.814 to 10.810 (0.04% variation). The absolute ratios are 7% lower than those reported by early workers, but are in accord with the results of recent investigations. Igneous rocks and boric acid are found to have high isotopic ratios, whereas Tokyo Bay water possesses a value for 11B/10B near the mean.

Lead isotopic fingerprinting of tectono-stratigraphic terranes, east-central Alaska

1987 ◽  
Vol 24 (10) ◽  
pp. 2089-2098 ◽  
Author(s):  
John N. Aleinikoff ◽  
Cynthia Dusel-Bacon ◽  
Helen L. Foster ◽  
Warren J. Nokleberg
Keyword(s):  
Isotopic Composition ◽  
Igneous Rocks ◽  
Isotopic Ratios ◽  
East Central ◽  
Isotopic Compositions ◽  
Common Lead ◽  
Crustal Origin ◽  
Lead Isotopic Ratios ◽  
Isotopic Fingerprinting

Common lead isotopic compositions have been determined on feldspars from meta-igneous rocks from nine tectono-stratigraphic terranes or subterranes in east-central Alaska. Most of the terranes have distinct and well-defined signatures in terms of isotopic composition; thus, most can be distinguished on conventional lead isotopic diagrams. Lead isotopic ratios provide evidence for (1) possible sources for the igneous rocks, (2) time of metamorphism, (3) correlation of terrane fragments, and (4) delineation of juxtaposed terranes. Determination of lead isotopic ratios from igneous rocks can be useful in characterizing tectono-stratigraphic terranes (as to mantle or crustal origin) and in correlation, particularly where terrane relationships are enigmatic.

Chemical variation in Al2O3–CaO–Na2O–K2O space: controls on the peraluminosity of the South Mountain Batholith

2004 ◽  
Vol 41 (7) ◽  
pp. 785-798 ◽  
Author(s):  
D Barrie Clarke ◽  
Michael A MacDonald ◽  
Saskia Erdmann
Keyword(s):  
Nova Scotia ◽  
Chemical Evolution ◽  
Wall Rock ◽  
Aqueous Fluid ◽  
Isotopic Ratios ◽  
Chemical Variation ◽  
The South ◽  
South Mountain Batholith ◽  
Upper Limit ◽  
Granitic Batholith

The South Mountain Batholith (SMB) of southwestern Nova Scotia is a large, highly differentiated, peraluminous, granitic batholith in which the average A/CNK (mol Al2O3/mol(CaO + Na2O + K2O)) increases from 1.16 to 1.23 with chemical evolution. We use vector analysis of variations solely in Al2O3–(CaO + Na2O + K2O) space to assess the fractionation, assimilation, fluid, and source controls on the peraluminosity of the SMB. With increasing chemical evolution, Al2O3 decreases, CaO decreases sharply, Na2O is approximately constant, and K2O increases in the early and middle stages but decreases in the most evolved stage. Initial 87Sr/86Sr and 143Nd/144Nd isotopic ratios for granites and average Meguma Supergroup country rocks suggest an upper limit of ~33% of wall-rock contamination for the most evolved rocks, if the most primitive rocks are uncontaminated. The trend of chemical evolution of the SMB through Al2O3–(CaO + Na2O + K2O) space is the resultant of all input vectors (processes). In the early stages, those processes are fractional crystallization of plagioclase ± K-feldspar ± cordierite ± biotite and contamination by country rocks. In the later stages, those processes are fractionation of plagioclase ± K-feldspar ± andalusite ± muscovite, further contamination by country rocks, and selective partitioning of Ca–Na–K into aqueous fluid phases. Clear geochemical evidence for variation in the source composition is lacking.

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