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BOLETÍN DE LA SOCIEDAD GEOLÓGICA MEXICANA http://dx.doi.org/10.18268/BSGM2011v63n3a10 |
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Análisis geológico y aeromagnético de las concentraciones anómalas de Fe en el plutón San Jerónimo en el Cinturón Batolítico Peninsular, Baja California, México
Geological and aeromagnetic analysis of anomalous Fe contents in the San Jerónimo pluton in the Peninsular Batholithic Belt, Baja California, Mexico
Xóchitl G. Torres Carrillo1,*, Luis A. Delgado Argote1, Juan M. Espinosa Cardeña1 y José M. Romo Jones1
1 División de Ciencias de la Tierra, CICESE, Ensenada, B.C., México, 22860.
*This email address is being protected from spambots. You need JavaScript enabled to view it..
Abstract
The San Jerónimo pluton belongs to the Peninsular Ranges Batholith. The modal composition indicates lithologies ranging from gabbro to granite. Curvilinear features interpreted from satellite images are related to the emplacement geometry of the pluton, and are less evident in the low viscosity mafic rocks. Because of the close relationship to the movement of magma, NE–SW oriented longitudinal fractures are closely parallel to magmatic foliation. The pluton is divided into the northern and southern zones based on the mafic/felsic rock ratio. In the northern part, magnetite–rich gabbro and diorite are dominant, and minor tonalite is characterized by its association with dikes with concentrations of more than 90% magnetite. In the southern part, mafic and felsic rocks show almost the same proportion and magnetite content diminishes. As expected, the magnetic susceptibility varies according to the magnetite content; in consequence, the intensity in the northern part is higher, and is directly associated to the presence of the magnetite–rich dikes. It is interpreted that the magnetite dikes result from early concentrations due to immiscibility in the mafic liquids, and that solid–state emplacement was induced by the younger felsic magma during its ascent.
Keywords: San Jeronimo pluton, Peninsular Ranges Batholiths, magnetic anomalies, magnetite.
