The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene

Details The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene

May 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29..362w&link_type=abstract

Meteoritics, vol. 29, no. 3, p. 362-373

Mathematics

Logic

20

Chondrites, Enstatite, Iron Oxides, Meteoritic Composition, Mineralogy, Oxidation-Reduction Reactions, Petrology, Pyroxenes, Reduction (Chemistry), Solar System Evolution, Graphs (Charts), Melting, Solid State, Solidification, Tables (Data), Trace Elements

Scientific paper

FeO-rich (Fs6-34) pyroxene lacking cathodoluminescence (CL), hereafter black pyroxene, is a major constituent of some of the chondrules and fragments in unequilibrated (type 3) enstatite chondrites (UECs). It contains structurally oriented zones of Cr-, Mn-, V-rich, FeO-poor enstatite with red CL, associated with mm-sized blebs of low-Ni, Fe-metal and, in some cases, silica. These occurrences represent clear evidence of pyroxene reduction. The black pyroxene is nearly always rimmed by minor element (Cr, Mn, V)-poor enstatite having a blue CL. More commonly, red and blue enstatites, unassociated with black pyroxene, occur as larger grains in chondrules and fragments, and these constitute the major silicate phases in UECs. The rare earth element (REE) abundance patterns of the black pyroxene are LREE-depleted. The blue enstatite rims, however, have a near-flat to LREE-enriched pattern, approx. 0.5-4x chondritic. The petrologic and trace element data indicate that the black pyroxene is from an earlier generation of chondrules that formed in a nebular region that was more oxidizing than that of the enstatite chondrites. Following solidification, these chondrules experienced a more reducing nebular environment and underwent reduction. Some, perhaps most, of the red enstatite that is common throughout the UECs may be the product of solid-state reduction of black pyroxene. The blue enstatite rims grew onto the surfaces of the black pyroxene and red enstatite as a result of condensation from a nebular gas. The evolutionary history of some of the enstatite and chondrules in enstatite chondrites can be expressed in a four-stage model that includes: Stage 1. Formation of chondrules in an oxidizing nebular environment. Stage 2. Solid-state reduction of the more oxidized chondrules and fragments to red enstatite in a more reducing nebular environment. Stage 3. Formation of blue enstatite rims on the black pyroxene as well as on the red enstatite. Stage 4.

Affiliated with

Also associated with

No associations

Rating

The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene 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 The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The evolution of enstatite and chondrules in unequilibrated enstatite chondrites: Evidence from iron-rich pyroxene will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-887796