Revision of the CaCO3–MgCO3 phase diagram at 3 and 6 GPa
Revision of the CaCO3–MgCO3 phase diagram at 3 and 6 GPa
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3 GPa 和 6 GPa 下 CaCO3-MgCO3 相图的修订
DOI：
10.2138/am-2018-6277
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发表时间：
2018
影响因子：
3.1
通讯作者：
K. Litasov
中科院分区：
文献类型：
--
作者：
A. Shatskiy;I. Podborodnikov;A. Arefiev;Daniil A. Minin;A. Chanyshev;K. Litasov
用Kawai型多砧装置在3和6 GPa压力下对CaCO_3-MgCO_3体系的亚固相线和熔化关系进行了重新研究。根据电子探针能量色散模式测量的相的化学组成和拉曼光谱鉴定的晶相来划分相边界。在3GPa下，菱镁矿-菱镁矿固溶线在约1250 °C下与熔融环相交，由此产生的等温三相线代表包绕反应：白云石（Ca# 43）=菱镁矿（Ca# 13）+液体（Ca# 48），其中Ca# = 100·Ca/（Ca+Mg）。CaCO 3-MgCO 3连接的熔化回路从1515 °C（CaCO 3）延伸到1515 °C（MgCO 3），通过在1230 °C（接近53摩尔% CaCO 3）的液相线最小值。从1425 °C开始，在系统中≤ 30摩尔%的CaCO 3下，液体淬火成树枝状碳酸盐和方镁石，并含有圆形空隙，表明不一致的熔融反应：MgCO 3（菱镁矿）= MgO（在液体中）+ CO2（流体和/或液体）。在6 GPa下，文石+菱镁矿组合在1000 °C以下是稳定的。文石+菱镁矿=白云石的反应温度在1000 ~ 1050 ℃之间。白云石的存在使该体系分裂为文石+白云石和白云石+菱镁矿两个部分二元体。菱镁矿-菱镁矿固溶线在1400 ~ 1450 °C之间与熔融环相交，由此产生的等温三相线代表包绕反应：白云石（Ca# 31）=菱镁矿（Ca# 21）+液体（Ca# 57）。CaCO 3-MgCO 3连接的熔融回路从1660 °C（CaCO 3）延伸到1780 °C（MgCO 3），通过在1400 °C和62摩尔% CaCO 3下的液相线最小值。碳酸盐榴辉岩（Yaxley和Brey 2004）和橄榄岩（道尔顿和Presnall 1998）系统实验中碳酸盐晶体和熔体的组成与3和6 GPa下CaCO 3-MgCO 3熔融环的几何形状一致：3 GPa下榴辉岩和橄榄岩中Ca-白云石熔体与Mg-方解石共存，6 GPa下白云石熔体与橄榄岩中菱镁矿共存。
Abstract Subsolidus and melting relationships for the system CaCO3–MgCO3 have been reexamined using a Kawai-type multi-anvil apparatus at 3 and 6 GPa in graphite capsules. Phase boundaries were delineated according to the chemical composition of phases measured by electron microprobe in energy dispersive mode and identification of crystal phases by Raman spectroscopy. At 3 GPa, the dolomite-magnesite solvus intersects the melting loop at about 1250 °C, and the isothermal three-phase line so produced represents the peritectic reaction: dolomite (Ca# 43) = magnesite (Ca# 13) + liquid (Ca# 48), where Ca# = 100·Ca/(Ca+Mg). The melting loop for the CaCO3–MgCO3 join extends from 1515 °C (CaCO3) to 1515 °C (MgCO3) through a liquidus minimum at 1230 °C (near 53 mol% CaCO3). Starting from 1425 °C at ≤ 30 mol% CaCO3 in the system, the liquid quenches to dendritic carbonate and periclase and contains rounded voids, indicating an incongruent melting reaction: MgCO3 (magnesite) = MgO (in liquid) + CO2 (fluid and/or liquid). At 6 GPa, aragonite + magnesite assemblage is stable up to 1000 °C. The reaction aragonite + magnesite = dolomite locates between 1000 and 1050 °C. The presence of dolomite splits the system into two partial binaries: aragonite + dolomite and dolomite + magnesite. The dolomite-magnesite solvus intersects the melting loop between 1400 and 1450 °C, and the isothermal three-phase line so produced represents the peritectic reaction: dolomite (Ca# 31) = magnesite (Ca# 21) + liquid (Ca# 57). The melting loop for the CaCO3–MgCO3 join extends from 1660 °C (CaCO3) to 1780 °C (MgCO3) through a liquidus minimum at 1400 °C and 62 mol% CaCO3. The compositions of carbonate crystals and melts from the experiments in the carbonated eclogite (Yaxley and Brey 2004) and peridotite (Dalton and Presnall 1998) systems are consistent with the geometry of the CaCO3–MgCO3 melting loop at 3 and 6 GPa: Ca-dolomite melt coexists with Mg-calcite in eclogite and peridotite at 3 GPa and dolomite melt coexists with magnesite in peridotite at 6 GPa.
影响因子：
3.1
作者：
K. Suito;Junpei Namba;T. Horikawa;Y. Taniguchi;N. Sakurai;M. Kobayashi;A. Onodera;O. Shimomura
通讯作者：
K. Suito;Junpei Namba;T. Horikawa;Y. Taniguchi;N. Sakurai;M. Kobayashi;A. Onodera;O. Shimomura
影响因子：
1.4
作者：
S. Ono;T. Kikegawa;Y. Higo
通讯作者：
S. Ono;T. Kikegawa;Y. Higo