CLINOPYROXENE JD BAROMETER FOR MANTLE PERIDOTITES AND ECLOGITES AND THERMAL CONDITIONS OF THE LITHOSPHERIC KEELS OF CRATONS AND THEIR SURROUNDINGS

Recent developing of monomineral thermobarometry (Ryan, 1997; Nimis, Taylor, 2000; etc.) do not solve all. New method uses exchange Di –Jd. Na reveal correlation with (Altot +Cr) (Kuligin et al., 1998) better then with AlVI + Fe3++Cr controlled by Si. KD=Na/Ca *Mg/(Al+Cr) from P was calibrated with >1000 associations of kimberlite deep seated inclusions. The equation P=0.04*Kd *ToC/(1-2.4*Fe)-5.5 gives the estimates correlating with P (McGregor,1974) P=-0.0068*P^2 +1.3538*P-0.35 (r=0.84). Resulting P ~1 correlates (r=0.91) with (MG74) ones. For shallow peridotites and eclogites more complex model KD=Na/Ca Mg/(AlIV+Cr+ Fe3-2*Ti) more precise appoximation to McGregor, 1974 is P=0.54*KD^(2/3)/(1+2.45*Fe) -5.3. ToC Nimis&Taylor,2000 approximated to Bertarnd&Mrcier,1985 with ToC=0.000001*T (NiTa2000)^2 +0.9575* T (NiTa2000) +107.01. Method reproduces OPx-based plots for Udachnaya (Pokhilenko et al, 1993, 2000; Boyd et al., 1997) and other localities. Kimberlites form marginal and rifted cratonic areas display hotter mantle conditions (Schmidtberger et al., 1999, Lee Rudnick,2000), younger kimberlites reveal gradually heating interior (Pokhilenko et al, 2000). Modified version reproduces mantle heating beneath Vitim (Ashchepkov et al., 1988), structure of Malaita mantle (Nixon, Boyd, 1979) etc. Jd barometer gives appropriate PT estimates for eclogites plotting them to cold geotherm parts. Reproducing of experimental data needs more precise coefficients. RBRF grants 99-05-65688. References Brey G.P., Kohler T., 1990. J.Petrol., 31:1353-1378. Bertrand P,Mercier JCC., 1985. EPSL, 76:122. Boyd FR.; Pokhilenko NP.; Pearson DG. et al. CMP,1997 128: 228-246. Kuligin SS., Pokhilenko NP.1998,7IKC Abstracts. Cape Town. p. 480- 482. Lee CT., Rudnick RL. Proceedings 7IKC, Nixon’s v. 2000, pp. 728-735. MacGregor, I.D., 1974. Am. Mineral. 59, 110–119. Nimis P., Taylor W.2000. CMP 139 :5, 541-554 Nixon PH (Ed.). 1973. Lesotho kimberlites. Cape Town. 350 p. Pokh1lenko NP, Sobolev NV, Kuligin S.S., Proceedings 7IKC, Nixon’s v. 2000 .664-676. Ryan CG.; Griffin WL.; Pearson Norman J. 1996, JGR B 101:3, 5611-5625. Schmidberger SS., Francis D. 1999, Lithos 48 1999, 195–216