Compilation of radiogenic isotope data in Mexico and their petrogenetic implications

Seven hundred and twenty-five Sr, two hundred and forty-three Nd and one hu ndred and fifty-one Pb isotopic ratios from seven different Mexican magmati c provinces were compiled in an extensive geochemical database. Data were a rranged according to the Mexican geological provinces, indicating for each province total number of analyses, range and mean of values and two times s tandard deviation (2 sigma). Data from seven provinces were included in the database: Mexican Volcanic Belt (MVB), Sierra Madre Occidental (SMO), Baja California (BC), Pacific Ocean (PacOc), Altiplano (AP), Sierra Madre del S ur (SMS), and Sierra Madre Oriental (SMOr). Isotopic values from upper mant le and lower crustal xenoliths, basement outcrops and sediments from the Co cos Plate were also compiled. In the MVB the isotopic ratios range as follo ws: Sr-87/Sr-86 0.703003-0.70841; Nd-143/Nd-144 0.512496-0.513098; Pb-206/P b-204 18.567-19.580; Pb-207/Pb-204 15.466-15.647; Pb-208/Pb-204 38.065-38.6 32. The SMO shows a large variation in Sr-87/Sr-86 ranging from similar to 0.7033 to 0.71387. Nd-143/Nd-144 ratios are relatively less variable with v alues from 0.51191 to 0.51286. Pb isotope ratios in the SMO are as follows: Pb-206/Pb-204 18.060-18.860; Pb-207/Pb-204 15.558-15.636; Pb-208/Pb-204 37 .945-38.625. PacOc rocks show the most depleted Sr and Nd isotopic ratios ( 0.70232-0.70567 for Sr and 0.512631-0.513261 for Nd). Pb isotopes for PacOc show the following range: Pb-206/Pb-204 18.049-19.910; Pb-207/Pb-204 15.42 5-15.734; Pb-208/Pb-204 37.449-39.404. The isotopic ratios of the AP rocks seem to be within the range of those from the PacOc. Most samples with reported Sr and Nd isotopic data are spread within and ar ound the "mantle array". The SMO seems to have been formed by a mixing proc ess between mantle derived magmas and continental crust. The MVB appears to have a larger mantle component, with AFC as the dominant petrogenetic proc ess for the evolved rocks. There is still a need for Pb isotopic data in al l Mexican magmatic provinces and of Nd isotopes in BC, AP, SMS, and SMOr.