Hydrogen concentrations and He isotopes in olivine from ultramafic lamprophyres provide new constraints on a wet Tarim plume and Earth's deep water cycle

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26110%2F22%3APU147280" target="_blank" >RIV/00216305:26110/22:PU147280 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1029/2022JB024961" target="_blank" >https://doi.org/10.1029/2022JB024961</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1029/2022JB024961" target="_blank" >10.1029/2022JB024961</a>

Result language

angličtina

Original language name

Hydrogen concentrations and He isotopes in olivine from ultramafic lamprophyres provide new constraints on a wet Tarim plume and Earth's deep water cycle

Original language description

Water enters Earth's mantle via subduction of hydrated oceanic slab and largely returns to the ocean-atmosphere system through arc volcanism. However, the extent to which H2O is transferred into the deep mantle is poorly constrained. Here, we address this question by combining mineral chemistry and bulk-rock geochemistry data for aillikites related to the deep mantle plume which generated the Permian Tarim large igneous province (NW China). The water contents of olivine phenocrysts are 75–168 ppm H2O and positively correlated with Ti contents. These results, combined with infrared hydroxyl peaks at 3,572 and 3,525 cm−1, suggest that H is mainly present in the form of Ti-clinohumite-like point defects. Hydrogen concentration profiles across olivine reveal that H loss during decompression was limited to the outermost rims, and yield dehydration durations of 15–417 min. Based on the water contents of the highest-Fo olivine cores, the water contents of the primitive aillikite melts and their mantle source are estimated as 1.6–4.7 wt% and 150–1,200 ppm H2O, respectively. 3He/4He ratios (5.31–5.84 Ra) of olivine phenocrysts are slightly lower than MORBs and suggest involvement of recycled slab containing U (and hence radiogenic 4He) in the plume source. This interpretation is consistent with Pb isotope compositions of the aillikites which are intermediate between PREMA (Prevalent Mantle) and EM (Enriched Mantle) compositions. These lines of evidence combined with the depleted Sr-Nd isotopes and moderately radiogenic Os isotopes of the aillikites suggest that water in these rocks derived from a plume source marginally contaminated by deeply subducted hydrated material.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10505 - Geology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2022

Confidentiality

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

Name of the periodical

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH

ISSN

2169-9313

e-ISSN

2169-9356

Volume of the periodical

127

Issue of the periodical within the volume

12

Country of publishing house

US - UNITED STATES

Number of pages

20

Pages from-to

„“-„“

UT code for WoS article

000924521500001

EID of the result in the Scopus database

2-s2.0-85145170959