Abstract

The Branchville pegmatite is a distinctly zoned body that has a complex history. In the first stage the following zones appear to have formed by successive deposition from the walls inward: border zone, muscovite-quartz zone, perthite zone, and quartz core. In the second stage, replacement bodies composed of cleavelandite-quartz, cleavelandite, and cleavelandite-spodumene were developed, at the expense of the zones, along the interzonal contacts. Books of sheet-bearing mica were replaced in parts of the muscovite-quartz zone and most of the microcline-perthite zone was replaced by cleavelandite and quartz. The third stage consisted of supergene alteration of previously formed minerals by circulating ground water.

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