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首页> 外文期刊>Mineralium Deposita >Fault zone evolution and its controls on ore-grade distribution at the Jian Cha Ling gold deposit, western Qinling region, central China
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Fault zone evolution and its controls on ore-grade distribution at the Jian Cha Ling gold deposit, western Qinling region, central China

机译：中国西部秦岭地区剑叉岭金矿床断裂带演化及其对矿石品位分布的控制

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摘要

The Jian Cha Ling gold deposit is sited in folded and faulted Palaeoproterozoic rocks of the uplifted Mian-Lue-Yang block, adjacent to the Mianlue suture zone within the West Qinling mineral province, along the northern margin of the South China craton. Early Mesozoic gold mineralization at Jian Cha Ling, which has a pre-mined resource of about 536,000 oz Au, is controlled by the so-called F1 45 fault. The fault is a generally steeply N-dipping, WNW-trending deformation zone that is the result of dislocation along bedding planes, early foliation and axial planar surfaces of regional folds. The fault zone marks the contact between serpentinized, lower greenschist-facies dunites, harzburgites and minor gabbroic units in the footwall, and a metasedimentary sequence in the hanging wall that is dominated by metadolomite, metalimestone and phyllitic schists. Brittle–ductile deformation, partitioning of strain along pre-existing zones of weakness, and the formation of intrashear zone lozenges contributed to the development of a complex fault zone geometry. Variations in both dip and strike of discrete dislocation surfaces related to oblique, sinistral–reverse movement along the F1 45 fault zone focussed auriferous hydrothermal fluids along three dominant structural orientations. Gold was preferentially deposited along shallowly NNE-dipping and shallowly to moderately NNW-dipping fault segments, and is also associated with shallowly WSW-dipping, dolomite-dominated vein sets. Disseminated, economic gold grades (>4 g/t Au) are restricted to the footwall ultramafic rocks to within about 5 to 10 m of the contact with the hanging wall. Gold is related to laminated, realgar- and orpiment- bearing sheeted veins and hydrothermal breccias, as well as slickolites and fault gouge. Gold-bearing vein sets are located within the relatively undeformed, ultramafic intrashear zone lozenges. Gold-related alteration is dominated by extremely fine-grained, arsenic-bearing sulphide minerals and dolomite, with additional white mica and clay minerals. The structural setting of the deposit, combined with published data on the geological evolution of the West Qinling mineral province, suggest that the Jian Cha Ling gold deposit developed in an uplifted basement block during the final phases of northward subduction and suturing of the South China craton with the South Qinling orogen along the Mianlue Suture Zone, during the changeover from a compressional to transpressional tectonic regime in Late Triassic to Middle Jurassic times.
机译：剑叉岭金矿床位于华南克拉通北缘，与西秦岭矿产省的绵鹿缝合带相邻，位于隆起的绵乐阳洋地块的褶皱断层古生代岩石中。建岔岭的中生代早期金矿化是由所谓的F1 45 断层控制的，该矿的预采资源约为536,000盎司金。断层通常是陡峭的N倾，WNW趋势变形带，这是沿着层理平面，早期叶面和区域褶皱的轴向平面错位的结果。断层带标志着下盘蛇形化的低绿片岩相的dunites，哈茨伯格岩和次辉长岩单元之间的接触，以及由白云母，金属灰岩和页岩片岩为主的悬挂壁中的变质沉积序列。脆性-韧性变形，沿先前存在的薄弱区域的应变分配以及剪切内区域含片的形成，导致了复杂断层带几何的发展。与沿着F1 45 断裂带的斜向，左旋-反向运动有关的离散位错表面的倾角和走向的变化都集中于沿三个主要结构方向的含铁热液。优先在浅NNE浸入和浅至中度NNW浸入断层段沉积金，并且还与浅WSW浸入，白云岩为主的脉集有关。散布的经济金牌号（> 4 g / t Au）仅限于底盘超镁铁质岩石与悬壁接触的大约5至10 m之内。黄金与层状，雄黄和雌黄形成的片状脉和热液角砾岩以及滑石和断层泥有关。含金脉组位于相对未变形的超镁铁内剪切带锭剂中。与金有关的蚀变以极细粒，含砷的硫化物矿物和白云石以及其他白云母和粘土矿物为主导。该矿床的构造背景，再加上有关西秦岭矿区地质演化的公开数据，表明在南俯冲和缝合华南克拉通的最后阶段，尖竹岭金矿床在一个隆起的基底块中发育。在晚三叠世至侏罗纪中期，从绵勒缝合带沿南秦岭造山带转变为压变构造型。

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