Crystallographic control on lithium isotope fractionation in Archean to Cenozoic lithium-cesium-tantalum pegmatites

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F16%3A00000072" target="_blank" >RIV/00025798:_____/16:00000072 - isvavai.cz</a>

Alternative codes found

RIV/00216224:14310/16:00088761

Result on the web

<a href="http://geology.gsapubs.org/" target="_blank" >http://geology.gsapubs.org/</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1130/G37712.1" target="_blank" >10.1130/G37712.1</a>

Result language

angličtina

Original language name

Crystallographic control on lithium isotope fractionation in Archean to Cenozoic lithium-cesium-tantalum pegmatites

Original language description

The age distribution of LCT pegmatites largely overlaps with major phases of collisional orogenic events and assembly of super-continents. Some of the largest known LCT pegmatite deposits formed in very short intervals, 2.7-2.5 and 1.9-1.8 billion years ago (Ga), corresponding to two major pulses of continental crust growth. However, the exact process of generation and segregation of large volumes of Li-bearing pegmatite liquids, perhaps involving disequilibrium fractional crystallization and leaving residual melts enriched in fluxing elements such as B, F, H2O, Li, and P, remains largely obscure. The new data on Li contents and isotope compositions in major mineral phases from temporally and geographically separated pegmatite bodies document extreme variations in d7Li values among individual large LCT pegmatites, in particular Archean occurrences. The observed >10‰ variations in d7Li values for the same mineral phases from different localities (i.e., beryl, petalite, spodumene, lepidolite, amblygonite, muscovite) contrast with globally homogeneous Li isotope systematics of major mineral phases from unmodified mantle rocks. Consistent Li isotope offsets between coexisting mineral phases are best explained by Li isotope fractionation as a function of the bond length between Li and neighboring ions (O, OH, F). We suggest that spatially distinct Li isotope patterns act as fingerprints for different pegmatites and can be explained by the pre-existing Li isotope differences of their crustal sources at the time of pegmatite formation owing to differences in crustal age and evolution. This would imply secular evolution of the continental crust over Earth history toward present-day globally broadly uniform crustal 7Li/6Li ratios (d7Li ~0‰). The differences among Archean occurrences could reflect possible Archean paleogeography and perhaps be linked with different thermal regimes of individual cratons as a consequence of variations in crustal thickness.

Czech name

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Czech description

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Type

J_x - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)

CEP classification

DD - Geochemistry

OECD FORD branch

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Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2016

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Geology

ISSN

0091-7613

e-ISSN

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Volume of the periodical

44

Issue of the periodical within the volume

8

Country of publishing house

US - UNITED STATES

Number of pages

4

Pages from-to

655-658

UT code for WoS article

000380121500016

EID of the result in the Scopus database

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