Palaeomagnetic study of mesozoic rocks from Ixtapan de la Sal, México

Abstract

Palaeomagnetic data from 25 hand samples collected from three localities of a sequence of metavolcanic rocks exposed in southern 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 54.1°N, 139.1°E (dp = 10°, dm= 7°). The  magnetization is carried by high coercitivity minerals, possibly by secondary haematite. K-Ar dating of samples from two sites gives dates of 108 ± 5 Myr and 125 ± 5 Myr, 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.