PYROPHYLLITE – ZUNYITE – DIASPORE MINERALIZATION AT CHOUICHIAT, ANTI-ATLAS, MOROCCO
PYROPHYLLITE – ZUNYITE – DIASPORE MINERALIZATION AT CHOUICHIAT, ANTI-ATLAS, MOROCCO
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摩洛哥 ANTI-ATLAS 的 CHOUICHIAT 的叶蜡石 – ZUNYITE – 水硬铝石矿化
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
E. Marcoux
中科院分区：
文献类型：
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作者：
S. Berrada;A. Belkabir;E. Marcoux
Chouichiat 铝质结构位于 Bou Azzer – El Graara（摩洛哥中部安提阿特拉斯）的北部地区，露头为不连续的白色山脊，宽 10 至 60 m，东西延伸超过 2 km。该结构与一个大型逆向陡倾剪切廊道重合，其特征是穿透性片理和褶皱。由于流纹英安岩原岩的变质作用、热液蚀变和变形的综合作用，Chouichiat 结构表现出强烈的分带性。它具有 1) 中央石英-叶蜡石带，两侧包围 2) 富含叶蜡石-石英的近端带，含有少量水硬石、高岭石和遵尼石，以及斑点的赤铁矿，以及 3) 远端叶蜡石带，含有少量石英-叶蜡石、常见的赤铁矿和水铝石。该分区表示流纹英安石逐渐转变为叶腊石岩，剪切带的发育增强了这种转变，由于流体-岩石反应，强烈增加了渗透率。这种相互作用由一组反应来表示，其中最重要的是流英安石中的白云母水解生成叶腊石：2KAl 2 AlSi 3 O 10 (OH) 2 + 6 SiO 2 + 2H + → 3Al 2 Si 4 O 10 (OH) 2 + 2K + 。温度下降和二氧化硅活性增加导致早期水硬铝石被叶腊石取代。遵义岩随后结晶，主要在近端和远端区域之间的界面处，以及纤维放射状赤铁矿的壮观的玫瑰花结。主要的高岭石 - 叶腊石 - 石英组合可能是在 273° ± 10°C 和 1 kbar 左右生成的。质量平衡计算表明，由于硅酸铝的水解，移动元素显着浸出，促进了铝的残留浓度，并且二氧化硅大量添加。叶蜡石 - 一水硬铝石 - 遵尼岩组合是热液蚀变的铝长英质火山岩的特征，与含金浅成热液矿床相关的酸性流体蚀变的岩石非常相似。
The Chouichiat peraluminous structure, located in the northern domain of the Bou Azzer – El Graara (Central Anti-Atlas, Morocco), outcrops as a discontinuous whitish ridge 10 to 60 m wide extending E–W for more than 2 km. This structure coincides with a large reverse-sense steeply dipping shear corridor, marked by penetrative schistosities and folds. The Chouichiat structure displays a strong zoning due to the combined effects of metamorphism, hydrothermal alteration, and deformation of a rhyodacite protolith. It has 1) a central quartz–pyrophyllite zone, surrounded on both sides by 2) a pyrophyllite–quartz -rich proximal zone with small amounts of diaspore, kaolinite and zunyite, and spots of hematite, and 3) a distal pyrophyllite zone with quartz–pyrophyllite in smaller amounts, common hematite and diaspore. The zoning expresses the gradual transformation of rhyodacite to pyrophyllitic rocks, enhanced by the development of the shear zone, which has strongly increased the permeability owing to fluid–rock reaction. Such an interaction is represented by a set of reactions, the most important of which is the hydrolysis of white mica in the rhyodacite to produce pyrophyllite: 2KAl 2 AlSi 3 O 10 (OH) 2 + 6 SiO 2 + 2H + → 3Al 2 Si 4 O 10 (OH) 2 + 2K + . A decrease in temperature and an increase in silica activity led to replacement of early diaspore by pyrophyllite. Zunyite crystallized later, mostly at the interface between proximal and distal zones, together with spectacular rosettes of fibroradial hematite. The main kaolinite – pyrophyllite – quartz assemblage likely was generated around 273° ± 10°C and 1 kbar. Mass-balance calculations indicate a significant leaching of mobile elements, promoting the residual concentration of Al, and a substantial addition of silica, both due to hydrolysis of aluminum silicates. The pyrophyllite – diaspore – zunyite assemblage is characteristic of hydrothermally altered aluminous felsic volcanic rocks and very similar to rocks altered by acidic fluid associated with gold-bearing epithermal ore deposits.