Petrographic, geochemical and mineralogical study of the San José de Lourdes fulgurite, Zacatecas, Mexico

  • Adela Margarita Reyes-Salas Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Consuelo Macías-Romo Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Fernando Ortega-Gutiérrez Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Eugenio Octavio Reyes-Salas Universidad Nacional Autónoma de México, Facultad de Química, Del. Coyoacán, 04510, Ciudad de México, México.
  • Daniel Flores-Gutiérrez Universidad Nacional Autónoma de México, Instituto de Astronomía, Del. Coyoacán, 04510, Ciudad de México, México.
  • Leticia Alba-Aldave Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Patricia Girón-García Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Jasinto Robles-Camacho Instituto Nacional de Antropología e Historia, Subdirección de Laboratorios y Apoyo Académico, Centro INAH Michoacán, México.
  • José Luis García-Martínez Universidad Nacional Autónoma de México, Instituto de Geología, Del. Coyoacán, 04510, Ciudad de México, México.
  • Karina Cervantes de la Cruz Universidad Nacional Autónoma de México, Facultad de Ciencias, Del. Coyoacán, 04510, Ciudad de México, México.
Keywords: Fulgurite, wollastonite, cristobalite, Si-Fe alloy, As-Ca, ballen quartz, Zacatecas, Mexico.

Abstract

Petrographic, chemical and mineralogical studies were performed on a fulgurite formed by melting of soil by lightning strike located at San José de Lourdes, northeast of Fresnillo, State of Zacatecas, Mexico. Polarizing microscopy, scanning electron microscopy with EDS, micro- probe WDS analyses, micro-Raman spectroscopy, X-ray diffraction and X-ray fluorescence were used as analytical methods. Most of the specimens are tubular and have a smooth, lustrous, black, glassy texture while the exterior is encrusted with soil grains. Internally, this fulgurite is partly composed of heterogeneous vesicular glass mostly of andesitic composi- tion containing fragments of skeletal crystals of wollastonite and unde- termined Fe- silicate, spheroids of SiO2 similar to ballen quartz within the glass. The presence of very fine and scarce grains of ilmenite, zircon, apatite, silver and gold besides some Si-Fe alloys (silicides) of variable composition and arsenic-calcium compounds (which is found for the first time in fulgurites) is also reported. We estimate that the temperatures of crystallization were above 1,700 °C considering into account the melting of quartz and presence of reduced phases.

Published
2017-11-29
Section
Articles