TY - JOUR
T1 - Merwinite in diamond from São Luiz, Brazil
T2 - A new mineral of the Ca-rich mantle environment
AU - Zedgenizov, Dmitriy A.
AU - Shatskiy, Anton
AU - Ragozin, Alexey L.
AU - Kagi, Hiroyuki
AU - Shatsky, Vladislav S.
N1 - Funding Information:
We are grateful to Ofra Klein-BenDavid, Mark Hutchison, and two anonymous reviewers for thorough reviews and useful suggestions and Ian Swainson for editorial handling, telling criticism, and comments. This work was supported by the Ministry of Education and Science of Russian Federation (project nos. 14.B37.21.0601 and 14.B25.31.0032), by the Russian Foundation for Basic Research (project nos. 12-05-33035 and 13-05-00628) and Integration Project of SB RAS (project no. IP16).
PY - 2014/2/1
Y1 - 2014/2/1
N2 - Diamonds from Juina province, Brazil, and some others localities reveal the existence of a deep, Ca-rich carbonate-silicate source different from ultramafic and eclogite compositions. In this study, we describe the first observation of merwinite (Ca2.85Mg0.96Fe0.11Si2.04O8) in a diamond; it occurs as an inclusion in the central growth domain of a diamond from the São Luiz river alluvial deposits (Juina, Brazil). In addition, the diamond contains inclusions of walstromite-structured CaSiO3 in the core and (Mg0.86Fe0.14)2SiO4olivine in the rim. According to available experimental data, under mantle conditions, merwinite can only be formed in a specific Ca-rich and Mg- and Si-depleted enviroment that differs from any known mantle lithology (peridotitic or eclogitic). We suggest that such chemical conditions can occur during the interaction of subduction-derived calcium carbonatite melt with peridotitic mantle. The partial reduction of the melt could cause the simultaneous crystallization of Ca-rich silicates (CaSiO3and merwinite) and diamond at an early stage, and (Mg0.86Fe0.14)2SiO4olivine and diamond at a later stage, after the Ca-Mg exchange between carbonatite melt and peridotite has ceased. This scenario is supported by the presence of calcite microinclusions within merwinite.
AB - Diamonds from Juina province, Brazil, and some others localities reveal the existence of a deep, Ca-rich carbonate-silicate source different from ultramafic and eclogite compositions. In this study, we describe the first observation of merwinite (Ca2.85Mg0.96Fe0.11Si2.04O8) in a diamond; it occurs as an inclusion in the central growth domain of a diamond from the São Luiz river alluvial deposits (Juina, Brazil). In addition, the diamond contains inclusions of walstromite-structured CaSiO3 in the core and (Mg0.86Fe0.14)2SiO4olivine in the rim. According to available experimental data, under mantle conditions, merwinite can only be formed in a specific Ca-rich and Mg- and Si-depleted enviroment that differs from any known mantle lithology (peridotitic or eclogitic). We suggest that such chemical conditions can occur during the interaction of subduction-derived calcium carbonatite melt with peridotitic mantle. The partial reduction of the melt could cause the simultaneous crystallization of Ca-rich silicates (CaSiO3and merwinite) and diamond at an early stage, and (Mg0.86Fe0.14)2SiO4olivine and diamond at a later stage, after the Ca-Mg exchange between carbonatite melt and peridotite has ceased. This scenario is supported by the presence of calcite microinclusions within merwinite.
KW - Earth's mantle
KW - Merwinite
KW - calcic lithology
KW - carbon
KW - diamond
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U2 - 10.1515/am.2014.4767
DO - 10.1515/am.2014.4767
M3 - Article
AN - SCOPUS:84894548706
VL - 99
SP - 547
EP - 550
JO - American Mineralogist
JF - American Mineralogist
SN - 0003-004X
IS - 2-3
ER -