THE 53MN-53CR CHRONOMETER HAS GREAT POTENTIAL FOR DATING AQUEOUS ALTERATION IN CHONDRITIC METEORITES. AQUEOUS ALTERATION PRODUCES MINERALS SUCH AS CALCITE AND FAYALITE WITH VERY HIGH MN/CR RATIOS AND SECONDARY ION MASS SPECTROMETRY (SIMS) CAN EASILY MEASURE THE 53CR EXCESSES IN THESE PHASES. UNTIL RECENTLY THE SIMS MEASUREMENTS HAVE NOT BEEN PROPERLY STANDARDIZED AND THE INFERRED CHRONOLOGY HAS BEEN CONFUSING. RECENTLY HOWEVER OUR GROUP AND DR. SUGIURA S GROUP IN JAPAN HAVE PUT A LOT OF EFFORT INTO PRODUCING MATRIX-MATCHED STANDARDS FOR MN-CR MEASUREMENTS. WITH THE NEW STANDARDS THE DATES FOR SECONDARY PHASES IN UOCS CM CV AND CR CHONDRITES HAVE CONVERGED ON ~ 4 MYR AFTER CAIS. WE WANT TO TAKE THIS WORK TO THE NEXT LEVEL. 1) WE WILL DEVELOP NEW STANDARDS FOR CALCITE AND DOLOMITE AND PERHAPS OTHER CARBONATES TO REDUCE THE UNCERTAINTIES FROM THE MN/CR RELATIVE SENSITIVITY FACTORS. THE NEW CALCITE STANDARD DEVELOPED BY SUGIURA S GROUP IS ZONED WHICH MAKES IT DIFFICULT TO USE. 2) WE WILL IMPROVE THE PRECISION OF 53MN-53CR MEASUREMENTS. CURRENTLY THE AGES DETERMINED FROM CARBONATES HAVE UNCERTAINTIES OF 20% - 33%. THIS IS BECAUSE OF LIMITED NUMBERS OF MEASUREMENTS ON A GIVEN SAMPLE AND RELATIVELY POOR PRECISION OF THE MEASUREMENTS. WE WILL TAKE SPECIAL CARE TO OBTAIN HIGH-PRECISION DATA. A NEW HYPERION II ION SOURCE WHICH IS THE SUBJECT OF A PME PROPOSAL TO EMERGING WORLDS WOULD GREATLY FACILITATE THIS WORK. TOGETHER IMPROVED STANDARDS AND IMPROVED MEASUREMENT PRECISION SHOULD REDUCE THE UNCERTAINTIES IN INITIAL 53MN/55MN RATIOS TO<10% (<~0.5 MYR IN THE AGES). 3) WE WILL PUT THE MEASUREMENTS OF CARBONATES AND FAYALITE INTO A BETTER PETROLOGIC CONTEXT. FOR EXAMPLE WE WILL LOOK FOR MULTIPLE GENERATIONS OF CARBONATES SUCH AS HAS BEEN DESCRIBED IN MET 01070 AND WE WILL LOOK FOR RELATIONSHIPS AMONG PHASES. OXYGEN ISOTOPES WILL BE USEFUL IN THIS WORK. THE NEW HIGH-PRECISION DATA AND DETAILED PETROLOGIC CONTEXT SHOULD PERMIT US TO EXTRACT DETAILED INFORMATION ON THE TIMING OF ALTERATION AMONG METEORITES OF A GIVEN CLASS AND PERHAPS AMONG LITHOLOGIC UNITS WITHIN A GIVEN METEORITE. WE WILL INITIALLY CONCENTRATE ON CARBONATES FROM CM CHONDRITES WITH SAMPLES REPRESENTING LEVELS OF AQUEOUS ALTERATION FROM CM2.7 TO CM2.0. WE WILL ALSO TRY TO EXTEND AND IMPROVE THE DATA ON CARBONATES FROM CR CHONDRITES. WE WILL THEN TURN TO UOCS LOOKING PRIMARILY AT FAYALITE. IN A CLOSELY RELATED STUDY WE WILL INVESTIGATE THE 60FE-60NI SYSTEM IN SECONDARY MINERALS FROM PRIMITIVE CHONDRITES. THERE IS CURRENTLY NO CONSENSUS ON THE ABUNDANCE OF 60FE IN THE EARLY SOLAR SYSTEM. SIMS MEASUREMENTS SUGGEST INITIAL 60FE/56FE RATIOS AS HIGH AS 1X10^6 WHILE BULK MEASUREMENTS OF METEORITES AND CHONDRULES SUGGEST INITIAL RATIOS BELOW 3X10^-8. THE MAIN PROBLEM SEEMS TO BE THAT FE AND NI ARE MOBILE UNDER THE CONDITIONS EXPERIENCED BY MOST METEORITES (TELUS ET AL. 2016). WE PROPOSE TO GET AROUND THIS PROBLEM BY MEASURING SECONDARY FE-RICH MINERALS (FAYALITE MAGNETITE HEDENBERGITE) THAT WERE PRODUCED BY THE SAME ALTERATION EVENTS THAT DISRUPTED THE 60FE-60NI SYSTEM IN THE PRIMARY PHASES (OLIVINE PYROXENE). IF THE INITIAL 60FE/56FE RATIO IN THE SOLAR SYSTEM WAS AS HIGH AS ~(1-2)X10^-7 WE SHOULD BE ABLE TO DETECT EVIDENCE OF 60FE IN SECONDARY MINERALS. PRELIMINARY MEASUREMENTS IN FAYALITE AND MAGNETITE FROM SEMARKONA (LL3.0) AND KABA (CV3) HAVE NOT GIVEN RESOLVED INITIAL RATIOS ALTHOUGH THE UPPER LIMITS ON THE INITIAL RATIOS ARE CONSISTENT WITH VALUES OF (0.5-2)X10^-7. WE HAVE IDENTIFIED A LARGE NUMBER OF SMALL FAYALITE GRAINS IN KAVA AND IN SEVERAL UOCS. ALTHOUGH THE GRAINS ARE SMALL CAN MEASURE MANY OF THEM. IF OUR PME PROPOSAL FOR A NEW HYPERION II O- SOURCE IS FUNDED WE WILL EASILY BE ABLE TO MEASURE A LARGE NUMBER OF THESE SMALL FAYALITE GRAINS AND DETERMINE THE LEVEL AT WHICH 60FE WAS PRESENT IN THE EARLY SOLAR SYSTEM.