Alteration And The Forming Dynamic Process Of The Qiyugou Breccia Gold Deposit

Field, petrographic work, microscope observations carried out on samples from the Qiyugou Au-bearing breccia pipes. Evidences from macro- and micro-textures suggest that the style of breccias in the area can be grouped into three types: 1) Type 1 with jigsaw fit - stockwork texture, in which the interval between clasts is marked by fractures or filled with calcite or quartz vein;in this type a little movement is observed between the clasts;2) Type 2 with that the larger breccias are supported by smaller breccias, rock flour and alteration materials;in this type clasts moved for a distinguishable distance, creating open spaces;3) Type 3 with fluidized texture: here the clasts are of different lithologies have rounded shapes and lesser domino texture. The large distant movement is observed between clasts. Gold mineralization occurs as disseminations, in stockwork veins, openspace infills. The ore zones form subparallel sheets that are nearly perpendicular to the walls of the pipes. These observations are consistent with those resulting from experiments on fluidization processes reported in the literature. These results strongly suggest that fluidization is an important geological process in formation of the Qiyugou Au-bearing breccia pipes and gold mineralization. Processes of expandion, bubbling, slugging, channeling and spouting of fluidization must have contributed to the formation in Qiyugou breccia pipes and were conducive to the development of gold mineralization.Based on results obtained from field observations, petrographic analysis, laser Raman microspectroscopy and microprobe analysis carried out on samples from the Au-bearing Qiyugou breccia pipes, new discovery of an adularia-calcite assemblage is recognized in the breccia gold deposit. Two stages of gold mineralization in the breccia pipes, pervasive and vein, are distinguished. The pervasive alteration of actionlite, green biote, epidote, chlorite and minor sericite in early replace the breccias and rock flour, and follow sequence of adularia and calcite filling the openspace. Vein ores associated with quartz, sericite, and minor calcite alteration occurs in NE-trending fault that cut pervasive ores. These results suggest that adularia-calcite alteration is paragenetic with gold mineralization. And New discovery ofadularia-calcite assemblage in the area suggest that the Qiyugou pipes are of low-sulphidation epithermal in nature This assemblage of adularia-calcite is also indicative of boiling zone within the level of lower temperature than 320°C, <1500m in depth for the formation of Qiyugou Au-bearing breccia pipes.The adularia-calcite assemblage is commonly located above the decompressive shock and clast - surpport breccias in spatial. The biotite + epidote alteration is predominated below the decopressive shock and clast - surpport breccias. The adularia-calcite with chlorite alteration forms in boiling condition of near-neutral hydrothermal. The decompressive shock breccia is representative of the hydrostatic process of abruptly lowing pressure during fluidization from expanding, bubbling to slugging. The abruptly lowing pressure is an effective mechanism for boiling. Therefore, this characteristics reflect the assemblage of adularia-calcite is an inevitable product of the fluidization process from expanding, bubbling to slugging.Lastly, a historic and genetic model of the Qiyugou Au-bearing breccia pipes and link with the porphyry Leimengou Mo deposit are proposed on the basis of the age data of granitoid, breccia pipe and mineralization events in the area.