Document Detail


Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle.
MedLine Citation:
PMID:  22869705     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO(3)-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth's surface.
Authors:
Marco Merlini; Wilson A Crichton; Michael Hanfland; Mauro Gemmi; Harald Müller; Ilya Kupenko; Leonid Dubrovinsky
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-08-06
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  109     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-08-22     Completed Date:  2012-10-31     Revised Date:  2013-07-12    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  13509-14     Citation Subset:  IM    
Affiliation:
Dipartimento di Scienze della Terra, Università degli Studi di Milano, Milano, Italy. marco.merlini@unimi.it
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MeSH Terms
Descriptor/Qualifier:
Calcium / chemistry
Calcium Carbonate / chemistry*
Carbon / chemistry*
Carbon Cycle*
Crystallization
Diamond
Earth (Planet)
Lasers
Magnesium / chemistry*
Pressure
Temperature
Thermodynamics
Chemical
Reg. No./Substance:
16389-88-1/dolomite; 471-34-1/Calcium Carbonate; 7439-95-4/Magnesium; 7440-44-0/Carbon; 7440-70-2/Calcium; 7782-40-3/Diamond
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