SPLITTING OF THE TWO WIIK LINES IN THE UREY-CRAIG FIELD: C-S ARE RELATED TO H-S LIKE AS LL-S ARE RELATED TO L-S. (STATISTICAL ANALYSES OF THE NIPR DATASET, VII)

From the NIPR meteorite chemical composition dataset we formed multicomponent functions to see thermal evolution (metamorphism) trends of chondrite parent bodies. We have found that the two Fecompound supergroups of Wiik split into two subgroups of (H and C) and (L and LL) in an evolutionary process along the van Schmus-Wood metamorphic sequence. FORMULATION OF THE PROBLEM: WHERE ARE THE ANCESTORS OF L-S? WITH WIIK'S SET (30), CAN NOT, WITH NIPR SET (500) CAN BE ANSWERED The Catalog of Antarctic Meteorites (Yanai, Kojima, Haramura, 1995) with its more than 550 "points" made it possible to restudy the possibility of the common origin of chondrites grouped by Urey & Craig (1953) and Wiik (1956) into two main total iron content lines. One line was split by Fredrickson and Keil to L and LL but the common origin for H and C supergroup was less emphasized. Since Fe-compounds belong to initial condition type parameters of chondrites, we considered the changes in mutual ratio of Fe-compounds as modifications by thermal evolution along the sequence milestoned by petrologic types. Going back to Wiik (1956), his developments on the Urey & Craig (1953) results was the following. Since chondrites seemed to form only 2 disjoint groups, H(igh) and L(ow) for total Fe content, Wiik selected 30 very careful measurements. He suggested to find ancestors of the developed chondrite groups. Explicitely he wanted to answer the question: what would be connection of the the H and L groups with the "primitive" C's. H found that all measured C's belonged to the H group (Fig. 1). So he could conclude that C's may be the "ancestors" of H's (and E's?), but not of L's. However, this was not the only and not a necessary conclusion. If all chondrite groups (at that time H and L) were independent, then it was also possible that L-s might have had other ancestor. If he concluded this direction then he could have put a question: If in an evolutionary scheme (where Fe/Si content is initial condition) why only H's can have precursors (Berczi & Lukacs, 1998), but precursors of L's can not be seen. After more than 4 decades answers can be formulated using the NIPR dataset (Fig. 2). HOW CAN WE STEP FORWARD FROM THE DEBATE BETWEEN THE GRADISTIC VS: CLADISTIC VIEWS IN EVOLUTIONARY CLASSIFICATION GRADISTIC VIEW: In evolution of biological systems gradistic viewpoint is traditional, when the gradual changes can be observed. Comparing grades (stages in a sequence) in an evolutionary process, "undeveloped", "primitive" stage is the initial one and for example for chondrites: volatile loss, equilibration of matrix and chondrules, fading of chondrule boundaries are the "gradually higher evolutionary stages". Different initial conditions (for other clads) may result in slightly different appearance of grades or different rate of approach to the grades similar. Fot example: diffusion will result in higher temperature for H than L having higher Mg content and so higher melting point for the olivine and pyroxene. CLADISTIC VIEW: In evolution of biological systems cladistic viewpoint means that we originally define initial conditions and sort objects to that initial condition. Later the clads develop according gradual processes, and new objects develop by branchings (bifurcations) of the clads. The evolution of clads (with different initial conditions) cannot merge. But if the clads were defined originally ambivalent, confusion arise and the branchings, (the bifurcated "main groups") want to mix for gradistic steps only. We think that the problem of the ancestor of L-s is at least partly a consequence of mixing the gradistic and cladistic viewpoints in meteoritics. In a gradistic viewpoint in a chondritic evolutionary process we compare grads so, that the C is synonimous with the name of the "undeveloped" or "primitive" stage, (with many volatile), then H (E) and L (LL) are the "higher evolutionary stages". In the cladistic view C may have gone "as far" as the others did from the startpoint, and then C3 (the "olivine-pigeonite chondrites, Brooks & Shaw, 1970) is comparable to H3 or LL3, or C6 (equilibrated) is comparable to H6; then the different initial conditions (for at least Fe and Mg (Berczi & Lukacs, 1997, [10]) support this view, because the evolution with different initial conditions cannot merge. At the same time, the cladistic/gradistic debate still lingers, because the main chondrite groups still have preserved their notations according to their gradistic meaning, too. OXIDATION/REDUCTION RACE HELP TO UNIFY THE TWO EVOLUTIONARY STRATEGIES Now we would like to see the cosequences of a common ancestor, split regional ancestor hypothesis. If two groups have common ancestor, but the volatile ratios are different, splitting of the evolutionary paths can be observed. We can get this structure of main chondrite group representatives along the van Schmus-Wood petrologic types, with Fe-compound ratios. Earlier we found such process when studied the oxidation/reduction race. (Lukacs, berczi, 1996.) Unfortunately, the NIPR Catalog does not give C components so we had to use a smaller statistics of Hayes (1974) and of Otting, Zahringer (1967) and we also accept the suggestion of Hutchison et al. (1987) and take Semarkona and Bishunpur as LL2. The average C contents are shown on Fig. 5., and Fig. 6. shows the valence equilibrated in colors (Fe=2, H=1 and C=4), where the reduced Fe is red, the C content is green and water content is blue. The color scales are independently normalized for each group. The maximal value within one group is 100.