Compilation of Radiogenic Isotope Data in Mexico and their Petrogenetic Implications

Journal of Earth system science

Ignacio S Torres-Alvarado1²  Gerardo Carrasco-Nunez2¹  Surendra P Verma11² 

[1] Instituto de Geología, UNAM, Circuito Exterior, Cd. Universitaria, 04510 Mexico, D.F., Mexico.$$;Centro de Investigacióon en Energía, UNAM, Priv. Xochicalco s/n, Col. Centro, Apdo. Postal 34, 62580 Temixco, Morelos, Mexico.$$

关键词: Radiogenic isotopes;    Sr;    Nd;    Pb;    magmatic provinces;    Mexico;    Pacific Ocean;    Cocos Plate.;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Seven hundred and twenty-five Sr, two hundred and forty-three Nd and one hundred and fifty-one Pb isotopic ratios from seven different Mexican magmatic provinces were compiled in an extensive geochemical database. Data were arranged according to the Mexican geological provinces, indicating for each province total number of analyses, range and mean of values and two times standard deviation (2𝜎). 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 Sur (SMS), and Sierra Madre Oriental (SMOr). Isotopic values from upper mantle and lower crustal xenoliths, basement outcrops and sediments from the Cocos Plate were also compiled. In the MVB the isotopic ratios range as follows: 87Sr/86Sr 0.703003-0.70841; 143Nd/144Nd 0.512496-0.513098; 206Pb/204Pb 18.567-19.580; 207Pb/204Pb 15.466-15.647; 208Pb/204Pb 38.065-38.632. The SMO shows a large variation in 87Sr/86Sr ranging from ~ 0.7033 to 0.71387. 143Nd/144Nd ratios are relatively less variable with values from 0.51191 to 0.51286. Pb isotope ratios in the SMO are as follows: 206Pb/204Pb 18.060-18.860; 207Pb/204Pb 15.558- 15.636; 208Pb/204Pb 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: 206Pb/204Pb 18.049-19.910; 207Pb/204Pb 15.425-15.734; 208Pb/204Pb 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 around the ``mantle array''. The SMO seems to have been formed by a mixing process between mantle derived magmas and continental crust. The MVB appears to have a larger mantle component, with AFC as the dominant petrogenetic process for the evolved rocks. There is still a need for Pb isotopic data in all Mexican magmatic provinces andofNdisotopes in BC,AP, SMS, and SMOr.

【 授权许可】

Unknown