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Neoarchean orogenic, magmatic and hydrothermal events in the Kalgoorlie-Kambalda area, Western Australia: constraints on gold mineralization in the Boulder Lefroy-Golden Mile fault system
Mineralium Deposita ( IF 4.8 ) Pub Date : 2016-08-06 , DOI: 10.1007/s00126-016-0665-9
Andreas G. Mueller , Steffen G. Hagemann , Neal J. McNaughton

The Boulder Lefroy-Golden Mile (BLF-GMF) fault system is the most intensely mineralized structure (>2150 t Au to 2015) in the Archean Yilgarn Craton, Western Australia. The fault system links the Kalgoorlie and Kambalda mining districts in the Eastern Goldfields Province, a continental-margin orogen subdivided into the western Kalgoorlie ensialic rift and the eastern Kurnalpi volcanic arc. After rifting, the 2.73–2.66 Ga greenstone-greywacke succession in the Kalgoorlie-Kambalda area underwent five phases of orogenic deformation, predominantly during ENE-WSW shortening: D1 upright folding at ca. 2680 Ma, D2 sinistral strike-slip faulting at 2678–2663 Ma, D3 folding of late conglomerate-turbidite successions at 2665–2655 Ma, D4 dextral strike-slip faulting at 2655–2640 Ma and D5 east-northeast-striking normal faulting. Regional prehnite-pumpellyite to greenschist facies burial metamorphism took place during D1 and D3 crustal thickening, and amphibolite facies aureoles formed around granite batholiths during and after D3 at 400 ± 100 MPa pressure. The D2 BLF offsets D1 folds by 12 km SW-side south and contains a porphyry dyke (2676 ± 7 Ma) boudinaged by transtensional oblique-slip along a line pitching 21° southeast. The BLF is linked by transverse D2 thrusts to other sinistral faults recording strike-slip until 2663 ± 7 Ma. Late D2 strike-slip movement alternated with early D3 shortening. D3 thrusts accommodated strain in fault blocks of rigid mafic-ultramafic volcanic rocks consolidated during D1, while the sedimentary rocks in D3 synclines were foliated at high strain. Biotite-sericite alteration and gold-pyrite mineralization in the BLF-GMF system took place at 11 ± 4 km burial depth in faults active during D2 and D3. The Golden Mile (1708 t Au) and other deposits are associated with stocks and dykes of high-Mg monzodiorite-tonalite porphyry, part of a late-orogenic (2665–2645 Ma) mantle-derived suite of adakitic affinity. Hornblende and apatite compositions indicate that these intrusions are characterized by high water contents (5–6 wt% H 2 O in melt), by high oxidation states (δNNO +1.0 to +2.4 log units) and by igneous anhydrite. Some stocks contain pervasive anhydrite-pyrite mineralization of low gold grade (0.4 g/t). Biotite-sericite-pyrite ore bodies such as those at Kanowna Belle (140 t Au) also replace faulted metamorphic rocks above batholith domes cored by plutons of the monzodiorite suite. The D4 strike-slip faults are barren at Kambalda but control gold quartz-vein ore at Kalgoorlie (2651 ± 9 Ma), and Au-Ag breccia ore at Black Flag (<2648 ± 6 Ma).

中文翻译:

西澳大利亚 Kalgoorlie-Kambalda 地区的新太古代造山、岩浆和热液事件:对 Boulder Lefroy-Golden Mile 断层系统中金矿化的限制

Boulder Lefroy-Golden Mile (BLF-GMF) 断层系统是西澳大利亚太古宙 Yilgarn Craton 中矿化最强烈的结构(>2150 t Au 至 2015 年)。断层系统连接东部金矿省的 Kalgoorlie 和 Kambalda 矿区,这是一个大陆边缘造山带,细分为西部 Kalgoorlie ensialic 裂谷和东部 Kurnalpi 火山弧。裂谷后,Kalgoorlie-Kambalda 地区的 2.73-2.66 Ga 绿岩-greywacke 序列经历了五个造山变形阶段,主要是在 ENE-WSW 缩短期间:D1 直立折叠约 2680 Ma,D2 2678-2663 Ma 左旋走滑断裂,D3 晚期砾岩-浊积岩系列褶皱2665-2655 Ma,D4 右旋走滑断裂,2655-2640 Ma,D5 东偏东走向正断层 在D1和D3地壳增厚期间发生区域性早长岩-菱镁矿到绿片岩相埋藏变质作用,在400±100 MPa压力下在D3期间和之后在花岗岩基岩周围形成角闪岩相光环。D2 BLF 偏移 D1 褶皱向南西南 12 公里,并包含一个斑岩岩脉 (2676 ± 7 Ma),沿一条向东南倾斜 21° 的线由张性斜滑移包围。BLF 通过横向 D2 逆冲断层与记录走滑的其他左旋断层相连,直到 2663 ± 7 Ma。D2 晚期走滑运动与 D3 早期缩短交替。D3 逆冲在 D1 期间固结的刚性基性-超基性火山岩断块中适应应变,而 D3 向斜中的沉积岩在高应变下叶理化。BLF-GMF 系统中的黑云母-绢云母蚀变和金-黄铁矿矿化发生在 D2 和 D3 期间活动断层的 11±4 公里埋藏深度。Golden Mile (1708 t Au) 和其他矿床与高镁二闪长岩 - 斑岩的储量和岩脉有关,这是晚造山(2665-2645 Ma)地幔衍生的埃达克岩亲合力套件的一部分。角闪石和磷灰石成分表明,这些侵入体的特点是含水量高(熔体中 5-6 wt% H 2 O)、高氧化态(δNNO +1.0 至 +2.4 log 单位)和火成岩硬石膏。一些库存含有普遍的低金品位硬石膏-黄铁矿矿化(0.4 克/吨)。黑云母-绢云母-黄铁矿矿体,例如 Kanowna Belle(140 吨金)矿体,也取代了以二长闪长岩岩体为核心的基岩穹顶上方的断层变质岩。
更新日期:2016-08-06
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