There was a question regarding the sorting of elements and why for example common chondrules had more iron than did Carbonaceous chondrites. The reason for the difference also includes why we use isotope ratios to determine from where a parent body probably formed within the solar system.
Sometime in early solar system development there was a sustained and or repeated strong solar wind or mini-nova, or perhaps our own ancestral sun's predecessor nearby supernova, or other cosmic water hose(?) that sweep through the swirling matter in the proto-solar disk, significantly sorting it out by elemental and molecular weights. Heavier particles weren't pushed out as far as the lighter ones. Thus we have heavy to light sorting of particles/ elements/ molecules/ solids/ gases etc from the inner rocky planets at one end to the giant gas planets beyond the asteroid belt and all way out to the Ort cloud. The sorting was not perfect but did rearrange the mixtures of elements locally. Conservation of angular momentum must have broken down at some level such that the Oort Cloud is theorized to be more or less spherical while planetary masses tend to lie close to the plane of the ecliptic. (This glitch influences measured elemental ratios of our known solar system and just mentioned for those paying attention) Thus before significant planetary accretion(first 3-5 million years?) we experienced a cycle of sorting that left zones of like particles to be accreted. This sorting also locally affected the ratios of the individual isotopes of elements from a concept we know as the Universal Abundance of the Elements.(UAE) (The UAE says that based on human measurements the mass of the universe is concentrated in the first 20 elements which incidentally were the main elements associated with living processes). When the local Solar system abundance of the UAE was disturbed, distribution of isotope ratios were also skewed in the local solar system. Ergo oxygen isotope studies in meteorites tell us what relative distance/radius a parent body formed away from the sun. On Earth the ratios for Oxygen: O18(Tritium)-O17(Deuterium)-O16 is something like 18O / 16O = 2005.20 ±0.43 ppm (a ratio of 1 part per approximately 498.7 parts) 17O / 16O = 379.9 ±1.6 ppm (a ratio of 1 part per approximately 2632 parts) This ratio signature is specific to an origin in the Earth Moon distance and there is a different one for Mars, the asteroid belt, Jupiter, Saturn and carbonaceous chondrites etc. Complications to this gradient include the amount of oxygen returned to earth via comets in what was known as the great bombardment-- back skewing the post shockwave sorting in the early sweep out. Ok we are at the end almost. O18 being two neutrons heavier takes more latent energy to vaporize and results in a slight concentration of its ratio in seawater depending on how much extra energy is around. The colder the climate the more O18 gets left behind in seawater and available for building carbonate seashells. The higher the temperature trends the more gets evaporated and a portion of that gets preserved in paleo-ice cores. Thus ratios differ in sequestrations such as in coral reefs and sea shells. This characteristic makes O18 content in ancient ice cores and fossil shells equivalent to a paleo thermometer. Long way around answering why some classes of meteorites have more iron in them than others. Elton ______________________________________________ http://www.meteoritecentral.com Meteorite-list mailing list [email protected] http://six.pairlist.net/mailman/listinfo/meteorite-list
