Mathematics – Probability
Scientific paper
Nov 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997gecoa..61.4557r&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 61, Issue 21, pp.4557-4569
Mathematics
Probability
11
Scientific paper
Melt impregnation and peridotite-melt interaction are ubiquitous phenomena in the oceanic-type lithospheric mantle. Nevertheless, the nature of the infiltrating melts is still poorly understood. We performed detailed textural and chemical investigations (by means of electron and ion microprobe) on: (1) impregnated plagioclase-bearing ophiolitic peridotites from the Internal Ligurides (Northern Apennine, Italy) and Mt. Maggiore (Corsica), and (2) olivine cumulates (consisting of 85 vol% olivine plus interstitial plagioclase and rare poikilitic clinopyroxene) from magmatic pods intruded within the Mt. Maggiore peridotites. Field evidence indicates that such cumulates crystallized from the melts, which impregnated the surrounding peridotites. Melt impregnation in the peridotites is verified by the occurrence of peculiar microstructures: (1) plagioclase blebs and/or veins confined along grain boundaries or crosscutting mantle minerals; (2) partial dissolution of mantle clinopyroxene and replacement by orthopyroxene and plagioclase aggregates, which indicate disequilibrium between melts and host peridotites. Interaction with melts also produces chemical modifications in mantle clinopyroxenes, i.e., Ti, M(middle)- to H(heavy)-REEs (and, to a lesser extent, Zr, Y, and Sc) enrichment coupled to depletion in Al. Minerals crystallized from the melts have depleted geochemical signature: plagioclases are highly Anorthitic (An 88 -An 94 in the peridotites; An 81 -An 85 in the cumulates), and show extremely low Sr (<26 ppm) and LREE (<1 × C1; Ce N /Sm N = 0.13-0.50) concentrations. Interstitial clinopyroxenes in the cumulates are characterized by high Mg values (90.6-91.7): their REE spectra show significant LREE depletion ( = 0.027-0.039), high M- to H-REE concentrations (15-30 × C1) and pronounced negative Eu N anomalies. Geochemical modeling indicates that the impregnating liquids probably consisted of unmixed depleted melt increments produced by 6-7% fractional melting. The results of this study therefore suggest that the impregnating melts originated at deeper mantle levels and presumably represented the last melt increments of a fractional melting process. There is thus a higher probability that they will remain incorporated in the upper mantle. They subsequently ascended, partly crystallized as cumulate pods, and interacted with the studied peridotites dissolving mantle clinopyroxene and precipitating orthopyroxene. Such a process has been increasingly invoked in studies of melt/rock reaction zones from ophiolitic peridotites.
Bottazzi Piero
Piccardo Giovanni B.
Rampone Elisabetta
Vannucci Riccardo
No associations
LandOfFree
Chemistry and origin of trapped melts in ophiolitic peridotites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Chemistry and origin of trapped melts in ophiolitic peridotites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chemistry and origin of trapped melts in ophiolitic peridotites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1687073