PETROGRAPHY AND GEOCHEMISTRY OF MAFIC LAVAS FROM THE NORTHERNMOST CINDER CONES OF THE CAMARGO VOLCANIC FIELD, CHIHUAHUA, MEXICO

The Camargo Volcanic Field (CVF) is considered the largest mafic cinder cone field in northern Mexico, within the Basin and Range physiographic province. CVF, located in the southeastern part of Chihuahua state, covers an area of around 3000 km² and it ejected about 120 km³ of mafic lavas, some with ultramafic and granulite xenoliths, from approximately 300 vents that formed from 4.7 to 0.009 Ma (Aranda-Gomez et al., 2003). Most of the previous work emphasized in the rock age, composition and isotopes of xenoliths. This study focusses in the geochemical composition of the mafic lavas from 2 of the CVF´s northernmost cinder cones. The volcanoes, called Espiritu Santo and Clavos, are considered part of the youngest group of vents, since the CVF´s volcanic activity began in the southwest part of the field and evolved to the northeast portion (Aranda-Gomez et al., 2003). Mafic lavas are classified as alkaline basalts with high contents of Sr (750-980 ppm), Cr (150-200 ppm), Ni (130-160 ppm), Cu (100-400 ppm), Zn (100-280 ppm) and Zr (160-220 ppm). The 2 cinder cones of this study: Espiritu Santo (ES) and Clavos (C), are 18 km away from each other, do not have any type of xenoliths, but there is a petrological difference between them. Espiritu Santo volcano have reddish lava flows (pahoehoe type) and medium to large volcanic bombs, all with aphanitic texture. The Clavos volcano contains both black and reddish lava flows (aa type) with two different presentations: a vesicular aphanitic basaltic scoria, and porphyritic lava flows, with olivine and clinopyroxene phenocrysts of almost 5 mm in size. This is the first study reporting geochemical data from these 2 cinder cones.