Lunar granite

The time of crystallization of a lunar "granite" has also been determined by the laser method. This "granite" is the K- and Si-rich felsite that forms clasts in 73215, 73255, and Boulder 1 at Station 2. The laser results set a lower limit of 4.00 G.y. on crystallization of the parent body of this felsite, and the Rb-Sr data set an upper limit of 4.05 G.y. [6]. 

Shih, C.-Y., Nyquist, L. E. and Wiesmann, H. (1994) K-Ca and Rb-Sr dating of two lunar granites relative chronometer resetting. Geochimica et Cosmochimica Acta, 58, 3101-3116. 

Ba and Th partitioning between 36. immiscible silicate melts further evaluation of role of silicate liquid immiscibility in the petrogenesis of lunar granites (abstract), Meteoritics, 24, 262,... 

Occurrence and Recovery. Rhenium is one of the least abundant of the naturally occurring elements. Various estimates of its abundance in Earth s cmst have been made. The most widely quoted figure is 0.027 atoms pet 10 atoms of silicon (0.05 ppm by wt) (3). However, this number, based on analyses for the most common rocks, ie, granites and basalts, has a high uncertainty. The abundance of rhenium in stony meteorites has been found to be approximately the same value. An average abundance in siderites is 0.5 ppm. In lunar materials, Re, when compared to Re, appears to be enriched by 1.4% to as much as 29%, relative to the terrestrial abundance. This may result from a nuclear reaction sequence beginning with neutron capture by tungsten-186, followed by p-decay of of a half-hfe of 24 h (4) (see Extraterrestrial materials). 

Jolliff B. L., Floss C., McCallum I. S., and Schwartz J. M. (1999) Geochemistry, petrology, and cooling history of 14161,7373 a plutonic lunar sample with textural evidence of granitic-fraction separation by silicate-liquid immisci-bility. Am. Mineral. 84, 821-837. 

The familiar continental crust of the Earth on which most of us live is of unique importance because it formed the platform above sea level on which the later stages of evolution occurred leading to the appearance of Homo sapiens. The conditions for the production of massive granitic cmsts are probably unique to the Earth and require three or more stages of derivation from a primitive mantle composition. The Earth has transformed less than 0.4% of its volume to continental cmst of intermediate composition and less than 0.2% of its volume into granitic continental crust (i.e., upper continental cmst) in over 4000 million years, so that the process is inefficient. The highland feldspathic crust of the Moon, about 12% of lunar volume, formed in contrast within a few million years. 

A peak in accurate trace element analysis appears to have been reached in the early 1970 s. There are three reasons for this. Firstly, the number of standard samples in circulation was small, with attention directed upon the six United States Geological Survey (USGS) standards (peridotite PCC-1, dunite DTS-1, basalt BCR-1, andesite AGV-1, granodiorite GSP-1 and granite G-2) which supplemented G-1 and W-1. Secondly, many new methods of analysis were being introduced, so that careful interlaboratory calibration was important to demonstrate the reliability of the new techniques. Thirdly, the arrival of the lunar samples placed a premium on high quality analyses of this unique material, access to the samples being denied to laboratories whose data were shown to be in error. The situation since that time has deteriorated, and the quality of many published trace element determinations appears to be little better than in the 1960 s. 

In addition to the studies cited above, there has been limited work on the partitioning of actinides between immiscible liquids. Dickinson and Jones [28] rqiorted a lunar basaltic liquid/granitic liquid partition coefficient for Th of 7 (1060 C, 1 bar, iron capsule). Jones et al. [71] reported carbonate liquid/silicate liquid partition coefficients for Pb, Ra, Pa, Th and U of 0.61, 0.15, 0.28 and 0.35, respectively (1250 C, 10 kbar, graphite capsule). 

This relationship tqypears to hold fiom 750 to 1500X and 2-6 kbar. However, Watstm and Harrison caution that the saturation equation is not a universal solution and does not describe the zircon saturation behavior observed by [76,137] in other systems. Additional zircon solubility measurements on a lunar basalt and granite compositions have been given by [27]. 

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