Computer Science
Scientific paper
Sep 1974
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1974gecoa..38.1329g&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 38, Issue 9, pp.1329-1330
Computer Science
26
Scientific paper
Lunar sample 76535 is a coarse-grained troctolitic granulite exhibiting a texture indicative of long annealing times. It is composed of homogeneous crystals of plagioclase (58 per cent, An 96 ), olivine (37 per cent, Fo 88 ) and bronzite (4 per cent, En 86 ). Chromian spinel-bronzite-diopside (Wo 46 En 50 Fs 4 ) symplectic intergrowths commonly occur along olivine-plagioclase boundaries and as tiny inclusions within olivine grains. These symplectites apparently formed by a reaction of the type: OI + An + Chromite Opx + Cpx + Al - Mg - chromite . The reaction is related to the experimentally determined reaction OI + An = Opx + Cpx + Sp of Kushiro and Yoder (1966). The enstatite content of the diopside coexisting with the bronzite indicates equilibration at about 1000°C. Thermodynamic calculations for 1000°C indicate that the symplectites formed at a minimum pressure of about 0.6 kb. Low alumina contents of the pyroxenes indicate equilibration near this minimum pressure. Clusters of the same assemblage found in the symplectic intergrowths, but containing accessory metal, troilite, Ca-phosphates, baddeleyite, plagioclase and/or K-feldspar occur sporadically throughout the rock. These apparent late stage products crystallized in the low temperature-high pressure region discussed above. Phase relations of co-existing metal phases indicate that the rock cooled at a few tens of degrees/my, corresponding to depths of 10-20 km below the lunar surface, in agreement with the above pressure estimate. We infer that 76535 represents an original cumulate deposited at a depth between about 10 and 30 km. The last liquid crystallized in the relatively high pressure-low temperature field opx + cpx + Al - Mg - chromite . Cooling was extremely slow and accompanied by extensive chemical and textural re-equilibration. Reaction to form the symplectites occurred during the late stages of re-equilibration.
Brett Robin
Gooley R.
Smyth Joseph R.
Warner Jeff
No associations
LandOfFree
A lunar rock of deep crustal origin: sample 76535 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 A lunar rock of deep crustal origin: sample 76535, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A lunar rock of deep crustal origin: sample 76535 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1584096