Palaeomagnetic study of Mesozoic rocks from Ixtapan de la Sal, Mexico.

Abstract

Palaeomagnetic data from 25 hand samples collected from 3 localities of a sequence of metavolcanic rocks exposed in S Mexico are reported. The samples show variable degrees of metamorphic and hydrothermal alteration resulting in green schists (2 sites) and altered andesites (1 site). After AF and thermal demagnetization the majority of samples show stable directions of normal and reverse polarities and yield a palaeomagnetic pole at 54.1oN, 139.1oE (dp=10o, dm=7o). The magnetization is carried by high coercivity minerals, possibly by secondary haematite. K-Ar dating of samples from 2 sites gives dates of 108+ or -5 Ma and 125+ or -5 Ma, which correlate with the event of regional compressive tectonism which affected the area. It is suggested that the stable remanences observed were acquired during the Late Jurassic to Early-Late Cretaceous. Comparison of the pole derived with Mesozoic pole positions reported for other areas in Mexico supports the possible occurrence of relative tectonic movements of the sampling area.-Authors