Partially sericitized tourmaline from a pegmatite was investigated using high-resolution transmission electron microscopy (HRTEM). Fine-grained muscovite crystals form extensive narrow veinlets preferentially developed along the {110} and {100} cleavages of tourmaline, indicating that a cleavage-controlled alteration mechanism was dominant. HRTEM images show that tourmaline-muscovite interfaces...

85 The physiography of the area is dominated by glaciated landforms carved in gneiss of the Fiordland Complex. The gneiss is generally dioritic, with gradations to quartzo-feldspathic and amphibolitic varieties, and is cut by mainly barren pegmatite veins; epidote is abundant. The rocks commonly show signs of post-consolidational shearing and crushing. There is a well defined zone of strongly c...

The physical behavior of silicate melts during the final stages of intrusion in the earth's crust are poorly understood. In particular, the low temperature limit of igneous petrogenesis is poorly constrained. The extreme differentiates of granitic magmatism that lead to pegmatite genesis span a very large range of composition not normally considered to be within the domain of igneous melt compo...

The Hellefjord Schist, a volcaniclastic psammite-pelite formation in the Caledonides of Arctic Norway contains discoidal impressions and apparent tube casts that share morphological and taphonomic similarities to Neoproterozoic stem-holdfast forms. U-Pb zircon geochronology on the host metasediment indicates it was deposited between 437 ± 2 and 439 ± 3 Ma, but also indicates that an inferred ba...

In this presentation questions are raised about a melt-restite unmixing model proposed by Barton and Sidle (1994) for the myrmekite-bearing Waldoboro granite complex along the southeastern coast of Maine (USA). This complex consists mostly of granite/granodiorite gneiss and granite, but smaller masses of quartz diorite, aplite, pegmatite, leucogranite, tourmaline granite, and granite porphyry o...