岡山県山宝鉱山産含カリウムヘイスティング閃石質普通角閃石

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The microprobe analyses of potassian hastingsitic hornblende from the pyrometasomatic ore deposit of the Sampo mine indicate the wider compositional variation range covering the compositional fields of hastingsitic hornblende and ferroedenitic hornblende. The most SiO_2-poor and SiO_2-rich analyses are : SiO_2 38.54,39.58; Al_2O_3 10.04,8.85; Fe_2O_3 6.26,6.04; FeO 26.70,26.16; MgO 1.11,1.36; MnO 0.53,0.41,CaO 11.46,11.73,Na_2O 1.04,1.01; K_2O 1.64,1.87; Cl 1.60,1.71; H_2O (calc.) 1.45,1.04; -O=Cl_2 0.36,0.39; totals 100.01%, 99.37%, respectively. These yield empirical formulae, respectively; (K_<0.34>Na_<0.33>)_<Σ0.67>Ca_<2.01>(Fe^<2+>_<3.65>Mg_<0.27>Mn_<0.07>)_<Σ3.99>(Fe^<3+>_<0.77>Al_<0.23>_<Σ1.00>(Si_<6.30>Al_<1.70>)_<Σ8.00>O_<21.98>((OH)_<1.58>Cl_<0.44>)_<Σ2.02> and (K_<0.39>Na_<0.32>)_<Σ0.71> Ca_<2.07>(Fe^<2+>_<3.61>Mg_<0.33>Mn_<0.06>)_<Σ4.00>(Fe^<3+>_<0.75>Al_<0.25>)_<Σ1.00>(Si_<6.53>Al_<1.47>)_<Σ8.00>O_<22.00>(O_<0.38>(OH)_<1.14>Cl_<0.48>)_<Σ2.00>. These are for the core and rim of a single prismatic crystal, respectively, and prove the existence of wider compositional variation range from a skarn accompanied by a granitic intrusion, which produced the pyrometasomatic ore deposit worked for iron and copper. The comparative study with similar clinoamphiboles from various skarns accomanying metallic mineralization informs that the higher contents of potassium and chlorine are characteristic to them, although a few analyses present lower potassium contents. The skarns involving such clinoamphiboles are accompanied by the mineralization of copper, zinc, arsenic, gold, etc. besides iron, and no specific relationship seems to exist. Clinoamphiboles of similar composition in igneous rocks are generally devoid of chlorine. It is very likely that chlorine in these minerals will be from ore-forming fluids together with sodium contained therein.
国立科学博物館の論文
1994-12-22

岡山県山宝鉱山産含カリウムヘイスティング閃石質普通角閃石

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