Chromian dravite associated with ultramafic-rock-hosted Archean lode gold deposits, Timmins-Porcupine District, Ontario
Chromian dravite associated with ultramafic-rock-hosted Archean lode gold deposits, Timmins-Porcupine District, Ontario
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安大略省蒂明斯-豪猪区，与超镁铁岩赋存的太古代矿脉金矿伴生的铬镁镁铁矿
作者：
R. King;R. Kerrich
在大多数情况下，与加拿大太古宙脉状金矿有关的电气石属于Schor！-Dravite固溶体系列；富铁成分往往占主导地位。然而，在安大略省蒂明斯-波丘派恩区的Beaumont地产和Buffalo铁白石矿中，发现电气石的铬和镁含量较高，足以被归类为铬黄铁矿(0.42-1.52 wt.OJoCrZ03‘8.08-8.74 wt.%MgO)。这些电气石的组成为：Mg&Gt；Fe&Gt；Cr和Na&Gt；Ca。相对较高的Al含量(~gt；6个原子/分子式单位)表明，在Y位上，而不是在Z位上，铬替代了镁。这两个产状在空间上都与蛇纹岩橄榄体和科马提质岩流有关。
In most instances, tourmaline associated with Canadian Archean lode gold deposits belongs to the schor!-dravite solid-solution series; Fe-rich compositions tend to predominate. However, at the Beaumont property and the Buffalo Ankerite mine in the Timmins-Porcupine district, Ontario, tourmaline is found whose elevated Cr and Mg contents warrant 'classification as chromian dravite (0.42-1.52 wt.OJoCrZ03' 8.08-8.74 wt.% MgO). These tourmaline compositions show Mg>Fe>Cr and Na>Ca. Relatively high AI contents (>6 atoms per formula unit) suggest Cr substitution for Mg in the Y site rather than for AI in the Z site. Both occurrences are spatially associated with serpentinized peridotite bodies and komatiitic flows.