Epizonal I- and A-type granites and associated ash-flow tuffs, Fogo Island, northeast Newfoundland

• Main Authors: Sandeman, HA, Malpas, J
• Format: Article in Journal/Newspaper
• Language: English
• Published: N R C Research Press. The Journal's web site is located at http://www.nrc.ca/cgi-bin/cisti/journals/rp/rp2_desc_e?cjes 1995
• Subjects: Earth sciences; Fogo; Fogo Island; Rogers Cove; Newfoundland
• Online Access: http://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0008-4077&volume=32&spage=1835&epage=1844&date=1995&atitle=Epizonal+I-+and+A-+type+granites+and+associated+ash-flow+tuffs,+Fogo+Island,+northeast+Newfoundland; http://hdl.handle.net/10722/42090

Magmatic activity of Silurian-Devonian age is widespread in the Appalachian-Caledonian Orogen. A marked characteristic of this magmatism is the composite nature of the igneous suites, which range from peridotite to granodiorite in single plutonic bodies. Such a suite of intrusive rocks, ranging in composition from minor peridotite to granodiorite, intrudes an openly folded sequence of Silurian volcanogenic sandstones and ash-flow tuffs on Fogo Island, northeast Newfoundland. Two units, the Rogers Cove and Hare Bay microgranites, consist of fine-grained hastingsite granites with spherulitic and flow-banded textures. These rocks have an A-type granitoid affinity. A third and the most voluminous granitic unit, the Shoal Bay granite exhibits mineral parageneses similar to the microgranites, but chemical characteristics more typical of calc-alkaline, I-type granitoids. Volcanic-sedimentary sequences spatially associated with the granitic rocks include dense, welded, high-silica, hastingsite-bearing ash-flow tuffs with compositions that suggest they represent erupted equivalents of fractionated end members of the Shoal Bay granite. -from Authors published_or_final_version