2 Sedimentology and Stratigraphy

Thursday, 1 April 2004
8:00 AM - 12:00 PM

SUGGESTED SOURCE FOR THE SANTA ROSA GROUP SEDIMENTS, EARLY PERMIAN, MAYA MOUNTAINS, BELIZE: A RARE EARTH ELEMENT DISTRIBUTION STUDY

Paper number: 2-7
Program: Technical Sessions
Time: 10:00 AM – 10:20 AM

Authors

Abstract

The striking similarity in the REE pattern of igneous rocks and the textural and compositional characteristics of the Santa Rosa Group sediments indicate that the likely predominant source of these Santa Rosa Group clastics is the local granite and granitoid rocks found regionally in the present day Maya Mountains. Chemical characterization plots, including La-Th-Sc and La/Th vs. Hf support a granitic to granitoid source of the Santa Rosa sediments, and the immobile element ratios of La/Sc, La/Co, Th/Sc, Th/Co, Th/Cr of the Santa Rosa clastics fall within the limits of sediments which originated from silicic igneous rocks. Textural and compositional thin section study of the analyzed Santa Rosa sandstones and Maya Mountain igneous rocks suggests that, following regional uplift, the long-term, intense tropical weathering of the Silurian Mount Pine and Hummingbird-Mullins River plutons, provided a substantial supply of sediment for the Permian sandstones. The textural characteristics of poor to moderate sorting, and the sub-angular to sub-rounded grains suggest a relatively short transportation history for these sediments, which is also consistent with these local plutons as sediment sources.

The presence of fine-grained authigenic euhedral pyrite, sphalerite, and galena, as well as, altered chlorites and sericite in the matrix of the sandstones suggest that secondary hydrothermal processes have been active in the study area, and are responsible for accumulation of the mobile trace elements including Cu, Zn, Pb, Ba, and Mo, in the sandstones, but have not been significant enough to alter or overprint the rare earth element signal.