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The Bravo Lake Formation is a mafic volcanic belt and large igneous province〔(Igneous rock associations in Canada 3. Large Igneous Provinces (LIPs) in Canada and adjacent regions: 3 ) Retrieved on 2007-01-10〕 located at the northern margin of the Trans-Hudson orogeny on central Baffin Island, Nunavut, Canada. It is exposed along a nearly continuous east-west passage for and changes in stratigraphic thickness from 1 to 2.5 kilometers.〔(Central Baffin Island 4-D Project - Projects ): Paleoproterozoic mafic magmatism in central Baffin Island. Retrieved on 2007-10-18〕 The formation is a rare alkaline-suite that formed as a result of submarine rifting during the Paleoproterozoic period.〔(Volcanology and geochemistry of the Bravo Lake Formation, Baffin Island, Nunavut ). Retrieved on 2007-10-18〕 The Bravo Lake Formation is surprisingly undeformed by the Himalayan-scale forming event during the Trans-Hudsonian orogeny. The stratigraphy of the Bravo Lake Formation starts with a basic section of iron-oxide rich sandstones, psammites, and semi-pelites which cover a series of deformed pillow lavas which expand in viscosity towards the west, and volcanic/clastic deposits and ultramafic sills. The lower volcanic section is covered by garnet and diopside bearing calc–silicate layers and finely layered metasediments composed of coarse-grained actinolite, hornblende and biotite followed by pelites and semi-pelites that are intruded by separate sills. In the Ridge Lake area, the volcanic belt includes an interlayered series of amphibolite, gabbro, iron formation, sulfidic schist and metasediments.〔 Geochemical results of pillow lavas and chill boundaries along five transects across the volcanic belt suggest the existence of three chemically different magma types within the Bravo Lake Formation.〔 Lavas of the volcanic belt display geochemical characteristics similar to modern ocean-island–basalt groups. They range from moderately to intensely fractionated. REE-profiles are similar to those from tholeiitic basalts to extremely alkaline lavas in Hawaii.〔 ==See also== *List of volcanoes in Canada *Volcanism of Canada *Volcanism of Northern Canada *Geography of Nunavut 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bravo Lake Formation」の詳細全文を読む スポンサード リンク
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