TY - JOUR
T1 - Reaction between MORB-eclogite derived melts and fertile peridotite and generation of ocean island basalts
AU - Mallik, Ananya
AU - Dasgupta, Rajdeep
N1 - Funding Information:
We are thankful to the editor Tim Elliott and two anonymous reviewers for their constructive reviews and to Claude Herzberg for informal comments. We acknowledge Ray Guillemette's assistance with electron microprobe analyses at TAMU. This work received support from NSF grant EAR-0911442 to RD.
PY - 2012/5/1
Y1 - 2012/5/1
N2 - We performed reaction experiments between partial melt of volatile-free MORB-eclogite and volatile-free fertile peridotite at 2.5-3GPa, 1375°C and 1440°C. The fraction of added basaltic andesite melt was varied from ~8 to 50wt.%. Melt was introduced either as a separate layer or mixed homogeneously with peridotite to simulate channelized and porous flow, respectively. Layered experiments produced a zone of orthopyroxene-rich garnet-websterite separating the reacted melt pool from a residual four phase lherzolite while mixed experiments produced a residual assemblage of orthopyroxene±clinopyroxene±olivine±garnet co-existing with reacted melt where residual olivine was absent only in the experiments with 50wt.% added melt. It is observed that the reacted melts display a continuous spectrum from tholeiitic to alkalic melts with increasing extent of wall-rock reaction for the layered runs and decreasing melt:rock ratio for the mixed experiments. The reacted melts at ~10-16wt.% MgO match better with natural alkali basalts and basanite from intraplate ocean islands in terms of SiO 2 (44-48wt.%), TiO 2 (2.2-4.1wt.%), Al 2O 3 (12.6-14.3wt.%), CaO (~8-11wt.%), Na 2O (~2-4wt.%), and CaO/Al 2O 3 (0.52-0.81) as compared to partial melts of volatile-free peridotite and MORB-eclogite. FeO* content (~9-11wt.%) of the reacted melts, however, remains poorer compared to most ocean island basalts (OIBs). We demonstrate that both alkalic and tholeiitic melts are produced in the process of MORB-eclogite partial melt and fertile peridotite reaction. We also demonstrate that near-primary alkali basalt can form at a temperature distinctly below the peridotite solidus and mantle potential temperature (T P) of ~1350°C may be sufficient to generate near-primary alkalic OIBs. Our study obviates the necessity for exotic lithologies, such as silica-deficient garnet pyroxenites, in the solid state mantle to explain the genesis of alkalic OIBs.
AB - We performed reaction experiments between partial melt of volatile-free MORB-eclogite and volatile-free fertile peridotite at 2.5-3GPa, 1375°C and 1440°C. The fraction of added basaltic andesite melt was varied from ~8 to 50wt.%. Melt was introduced either as a separate layer or mixed homogeneously with peridotite to simulate channelized and porous flow, respectively. Layered experiments produced a zone of orthopyroxene-rich garnet-websterite separating the reacted melt pool from a residual four phase lherzolite while mixed experiments produced a residual assemblage of orthopyroxene±clinopyroxene±olivine±garnet co-existing with reacted melt where residual olivine was absent only in the experiments with 50wt.% added melt. It is observed that the reacted melts display a continuous spectrum from tholeiitic to alkalic melts with increasing extent of wall-rock reaction for the layered runs and decreasing melt:rock ratio for the mixed experiments. The reacted melts at ~10-16wt.% MgO match better with natural alkali basalts and basanite from intraplate ocean islands in terms of SiO 2 (44-48wt.%), TiO 2 (2.2-4.1wt.%), Al 2O 3 (12.6-14.3wt.%), CaO (~8-11wt.%), Na 2O (~2-4wt.%), and CaO/Al 2O 3 (0.52-0.81) as compared to partial melts of volatile-free peridotite and MORB-eclogite. FeO* content (~9-11wt.%) of the reacted melts, however, remains poorer compared to most ocean island basalts (OIBs). We demonstrate that both alkalic and tholeiitic melts are produced in the process of MORB-eclogite partial melt and fertile peridotite reaction. We also demonstrate that near-primary alkali basalt can form at a temperature distinctly below the peridotite solidus and mantle potential temperature (T P) of ~1350°C may be sufficient to generate near-primary alkalic OIBs. Our study obviates the necessity for exotic lithologies, such as silica-deficient garnet pyroxenites, in the solid state mantle to explain the genesis of alkalic OIBs.
KW - Mantle heterogeneity
KW - Melt-rock reaction
KW - MORB-eclogite
KW - Ocean island basalts
KW - Peridotite
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U2 - 10.1016/j.epsl.2012.02.007
DO - 10.1016/j.epsl.2012.02.007
M3 - Article
AN - SCOPUS:84858733315
SN - 0012-821X
VL - 329-330
SP - 97
EP - 108
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -