The Grasshopper prospect, located 23 km west-southwest from Dillon, Montana, presents exposed zones of phyllic alteration assemblages comprising the early and late phyllic styles. The mineral chemistry of white micas from both phyllic alteration zones was evaluated by short-wave infrared spectroscopy, electron microprobe analysis, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The early phyllic expression consists of white to green micas characterized by longer Al-OH absorption wavelengths (2,204–2,210 nm), whereas the late phyllic phase contains white micas with shorter Al-OH absorption wavelengths (2,197–2,204 nm). Correlation with electron microprobe data found that the Tschermak substitution in the white micas is mainly controlled by Mg concentrations. Based on LA-ICP-MS data, higher Mn and Sr concentrations characterize white micas from the early phyllic alteration, whereas higher concentrations of B, Ba, Cr, Cs, Cu, Li, Rb, Sc, Sn, Ti, Tl, V, and W are present in white micas from the late phyllic style. Systematic zoning patterns of trace element concentrations in white micas from the early and late phyllic alteration styles were confirmed at Grasshopper. In general, increasing trends toward the center of the system were observed in V, Cu, Sc, Sn, W, and Zn, whereas increasing trends outward from the hydrothermal center were reported in Li and Cs. Comparison of the trace element concentrations of white micas from the early phyllic style from the barren system of Grasshopper and the mineralized system of Copper Cliff indicates significant differences in Zn, Cr, B, Tl, Sn, and Cs. Therefore, we propose a preliminary discrimination (Zn + Cr + B vs. Tl + Sn + Cs) plot that can be used to differentiate white micas from the early phyllic alteration among mineralized and weakly to unmineralized systems.

中文翻译：

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白云母地球化学：贫瘠和矿化斑岩系统的区分

Grasshopper矿区位于蒙大拿州狄龙市西南偏南23公里处，呈现出包括早期和晚期的叶栅样式在内的叶栅蚀变组合的裸露带。通过短波红外光谱法，电子微探针分析和激光烧蚀-电感耦合等离子体质谱法（LA-ICP-MS）评价了两个云母蚀变带中白云母的矿物化学。早期的叶状表达由白色至绿色的云母组成，特征是较长的Al-OH吸收波长（2,204–2,210 nm），而晚期的叶相包含白色的云母，具有较短的Al-OH吸收波长（2,197–2,204 nm）。与电子探针数据的相关性发现，白云母中的Tschermak取代主要受Mg浓度控制。根据LA-ICP-MS数据，较高的Mn和Sr浓度是早期云母突变引起的白色云母的特征，而较高的B，Ba，Cr，Cs，Cu，Li，Rb，Sc，Sn，Ti，Tl，V和W的浓度较高。晚种风格。在蚱Grass证实了来自早期和晚期的叶面蚀变样式的白云母中微量元素浓度的系统分区模式。通常，在V，Cu，Sc，Sn，W和Zn中观察到朝向系统中心的趋势增加，而在Li和Cs中观察到从热液中心向外的趋势增加。比较蚱hopper的贫瘠系统和铜崖矿化系统的早期叶状白云母的痕量元素浓度，表明锌，铬，硼，锡，锡和铯的显着差异。因此，