辽宁八家子三斜锰辉石的发现及其找矿意义

The Discovery of Pyroxmangite in Bajiazi Area of Liaoning Province and Its Ore_Hunting Implication

在对辽宁建昌县八家子矿区吴家屯铅锌黄铁矿－硫锰矿矿床进行研究的过程中，首次发现三斜锰辉石，它与锰铝榴石、硫锰矿、黄铁矿等共生，主要产出在铅锌黄铁矿体、硫锰矿体和近矿矽卡岩中。该区的三斜锰辉石为玫瑰红色和暗红褐色，短柱状，两组解理，折射率Ｎｇ＝１．７４９～１．７５３，Ｎｐ＝１．７３７～１．７４８，Ｎｍ＝１．７３４～１．７４１；＋２Ｖ＝４３°；ＤＯ＝３．７８６～３．７９２；ＤＣ＝３．７９～３．８３。化学成分除Ｓｉ外主要为Ｍｎ和Ｆｅ，矿物化学式：（Ｃａ０．２７～０．４３Ｍｇ０．４３～０．５７）０．７５～１．００（Ｍｎ４．９４～５．７７Ｆｅ０．３６～１．３６）６．１６～６．３７［Ｓｉ６．８６～７Ｏ２１］。晶体结构属三斜晶系，玫瑰红色三斜锰辉石的Ｘ射线衍射主要粉晶谱线：３．１３３（１００），２．９６０（４２），２．５０２（１３），２．１８３（１８），１．９１９（４５）。矿物成因研究表明，三斜锰辉石主要为岩浆岩与含锰白云岩接触交代作用的产物。

Pyroxmangite was discovered for the first time during the study of Wujiateng sec tion of the Bajiazi lead_zinc pyrite deposit in Laioning Province. Occurring com monly in lead_zinc pyrite orebodies and near_ore skarn, it is associated with sp essartine, pyrite and alabandite. Being reddish brown in color and short prismat ic in form, it has two sets of cleavages and refractivities of N g 1.749 ～1.753, N p 1.737～1.748, N m 1.734～1.741, (+)2 V 43° and D O 3.786～3.792. Chemical composition of the pyroxmangite depends largely on M n a nd Fe, which cause remarkable variation of its color. The mineral formula for th is mineral is (Ca 0.27～0.43 Mg 0.43～0.57 ) 0.75～1.00 (Mn 4.94 ～5.77 Fe 0.36～1.36 ) 6.16～6.37 [Si 6.86～7 O 21 ]. The mineral falls i nto the anorthic system and can be divided into two sorts of colors with differe nt X_ray powder diffraction patterns. The reddish brown mineral has X_ray spectr al lines of 3.133(100), 2.958(34), 2.503(7), 2.183(15) and 1.919(26) while the r ose red mineral shows 3.133(100), 2.960(42), 2.502(13), 2.183(18) and 1.919(45). Both sorts of pyroxmangite have such cell parameters as a =6.690～6.697, b =7.573～7.592, c = 17.41 ～ 17.40 , α =113.84 °～ 11 3.88° , β =82.35°～82.30° and γ =94.64°～94.74°. Its formation is related to the contact replacement between igneous rocks and Mn_containing dolom ite, and the Pb, Zn and S mineralization is so closely connected with the origin of pyroxmangite as to have ore_hunting significance.