Petrology and Inferred Tectonic Setting of the Mountain Pine Ridge Granitoids, Maya Mountains, Belize

Abstract

The Mountain Pine Ridge batholith is the largest of three major granitoid intrusions that crop out in the Maya Mountains of Belize. These plutons intrude a thick sequence of Upper Paleozoic metasedimentary and metavolcanic rocks known as the Santa Rosa Group. The mineralogy of the granitic rocks at Mountain Pine Ridge varies and the rocks are classified into four petrographic types—biotite leucogranite, muscovite leucogranite, granodiorite, and tonalite. The essential felsic minerals in these rocks include quartz, microcline, plagioclase feldspar ± perthite, and muscovite, whereas the only mafic mineral is biotite. Microprobe analysis shows that significant differences exist between the biotites of the different petrographic types, especially in the levels of Al(vi), Mn, Mg, total Fe, and the Fe/Fe+Mg ratio. Major, minor and trace-element chemistry of the four petrographic types indicates that the Mountain Pine Ridge batholith is composed of three different suites of granitic rocks. Although all three sui...