The Ok Tedi copper-gold mine in Western Province, Papua New Guinea, is situated in the western part of the Ok Tedi Complex where monzodiorite to quartz monzonite intrusions are associated with porphyry- and skarn-style copper-gold mineralization. The Pleistocene age of the intrusive rocks and mineralization provides an opportunity to study the longevity of the magmatic and hydrothermal evolution at Ok Tedi through U-Pb dating of zircon and high-precision Re-Os dating of molybdenite.Six main phases of intrusive rocks can be recognized within the mine area, with the sequence of intrusion indicated by contact relationships. Each has been dated by the SHRIMP U-Pb technique with correction for Th-U disequilibrium based on the U and Th content of each sample. In order of intrusion from oldest to youngest these include: Sydney Monzodiorite (1.368 ± 0.045 Ma), Warsaw Monzodiorite (1.269 ± 0.039 Ma), Kalgoorlie Monzodiorite (1.261 ± 0.050 Ma), Ningi Quartz Monzonite Porphyry (QMP)(1.229 ± 0.051 Ma), Bonn Quartz Monzonite (1.219 ± 0.040 Ma), and Fubilan QMP (1.213 ± 0.049 Ma). The intrusions are alkaline, high K to shoshonitic rocks with high Sr/Y ratios typical of Cu-fertile arc magmas. Chondrite-normalized REE patterns have minor or no negative Eu anomalies and downward sloping to listric-shaped HREE patterns typical of arc magmas in which high water contents supress plagioclase fractionation in favor of an evolution by hornblende ± garnet ± titanite fractionation.Cu-Au mineralization at Ok Tedi can be divided into four main stages based on crosscutting relationships: (1) skarn-endoskarn and associated vein-style mineralization in the Darai Limestone, Ieru siltstone, and Sydney Monzodiorite; (2) porphyry-style veins and breccias within the Ningi QMP and older intrusions, and at Siltstone Ridge: (3) porphyry-style veins and breccias in the Fubilan QMP and older intrusions: and (4) skarn-style mineralization in the lower part of the Darai Limestone along the Taranaki thrust. High-precision Re-Os dating of molybdenite has enabled a chronology to be established for the first three stages.Molybdenite from a quartz-mushketovite-epidote-carbonate-pyrite-chalcopyrite-molybdenite vein in clinopyroxene- and garnet-altered Sydney Monzodiorite has an age of 1.3206 ± 0.0020 Ma, and this dates the formation of the Gold Coast and Berlin skarns. Molybdenite from a quartz-pyrite-chalcopyrite-molybdenite vein in the sericite-altered Sydney Monzodiorite yields an age of 1.3166 ± 0.0043 Ma, and a quartz-pyrite-chalcopyrite-molybdenite vein with K-feldspar alteration selvages hosted in Ieru siltstone beneath the Gold Coast skarn has an age of 1.3031 ± 0.0015 Ma.Samples of molybdenite from quartz-sulfide veins from Siltstone Ridge have ages of 1.2116 ± 0.0029 and 1.2078 ± 0.0031 Ma. Molybdenite from a quartz-K-feldspar-pyrite-molybdenite vein, which overprints propylitic alteration in the Sydney Monzodiorite, has an age of 1.2120 ± 0.0024 Ma. These samples date porphyry-style mineralization in and around the Ningi QMP and at Siltstone Ridge. A sample of molybdenite from the matrix of hydrothermal intrusive breccia in the Fubilan QMP has an age of 1.2146 ± 0.0020 Ma, similar to the age of the adjacent Siltstone Ridge mineralization, and is interpreted to have been mechanically incorporated into the breccia during its formation.Several samples have been dated from the Fubilan porphyry system, including molybdenite from the matrix of a hydrothermal intrusive breccia (1.1648 ± 0.0020 Ma) and three samples from veins which postdate the breccias: a vuggy quartz-sulfide vein (1.1532 ± 0.0027 Ma), chalcopyrite-pyrite-molybdenite vein (1.1446 ± 0.0028 Ma), and duplicate analyses of a molybdenite-only vein (1.1326 ± 0.0034 and 1.1297 ± 0.0026 Ma) in agreement at 2σ.Molybdenite from a quartz-K-feldspar-biotite-magnetite-pyrite-chalcopyrite-molybdenite vein in endoskarn-altered Sydney Monzodiorite (beneath the Gold Coast skarn) has an age of 1.1459 ± 0.0012 Ma, and a similar vein without magnetite hosted in Warsaw Monzodiorite has an age of 1.1438 ± 0.0042 Ma, both within error of the chalcopyrite-pyrite-molybdenite vein in Fubilan QMP.Intrusive rocks in the Ok Tedi mine were emplaced over a period of approximately 200,000 years, with Cu-Au mineralization formed in discrete episodes of much shorter duration. The Gold Coast skarn and associated porphyry-style veins in Sydney Monzodiorite and Ieru siltstone formed in 14,000 to 21,000 years (n = 3), the Siltstone Ridge porphyry system in 2,000 to 12,000 years (n = 4), and the Fubilan porphyry system in 31,000 to 40,000 years (n = 6). The Taranaki skarn has not been dated in the mine area due to a lack of molybdenite, but geologic relationships indicate it is younger than the Fubilan QMP.

中文翻译：

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俯冲后环境中斑岩和矽卡岩型铜金矿化的快速形成：巴布亚新几内亚Ok Tedi矿的Re-Os和U-Pb年代学

西部省的巴布亚新几内亚的Ok Tedi铜金矿位于Ok Tedi Complex的西部，那里的闪长岩和矽卡岩型铜金矿化有辉闪石到石英辉绿岩的侵入。侵入岩和成矿的更新世年龄提供了一个机会，可以通过锆石的U-Pb测年和辉钼矿的高精度Re-Os测年研究Ok Tedi岩浆和热液演化的寿命。在矿区内被识别，并以接触关系表示入侵的顺序。每个都已通过SHRIMP U-Pb技术确定日期，并根据每个样品的U和Th含量对Th-U不平衡进行了校正。按照从大到小的顺序，包括：悉尼Monzodiorite（1.368±0。045 Ma），华沙Mondiodiorite（1.269±0.039 Ma），Kalgoorlie Mondiodiorite（1.261±0.050 Ma），Ningi石英Monzonite斑岩（QMP）（1.229±0.051 Ma），Bonn石英Monzonite（1.219±0.040 Ma）和Fubilan QMP（ 1.213±0.049 Ma）。侵入岩是碱性的，高钾含量的钾铁矿岩，具有高Sr / Y比的Cu肥沃弧形岩浆。球粒陨石归一化的REE模式具有较小或没有负Eu异常，并且向下倾斜至弧状岩浆典型的李斯特形HREE模式，其中高含水量抑制斜长石分馏，有利于角闪石±石榴石±钛矿分馏的演化。在Ok Tedi，根据横切关系可以分为四个主要阶段：（1）矽卡岩-内生矽卡岩以及相关的脉型矿化在达赖（Darai）石灰岩，艾鲁（Ieru）粉砂岩和悉尼Monzodiorite中；（2）Ningi QMP内的斑岩型脉和角砾岩和较早的侵入体，以及粉砂岭：（3）Fubilan QMP内的斑岩型脉和角砾岩和较老的侵入体；以及（4）下部的矽卡岩型矿化塔拉纳基逆冲的达赖（Darai）石灰岩的一部分。辉钼矿的高精度Re-Os测年可以确定前三个阶段的年代学。年龄为1.3206±0.0020 Ma，这可追溯到黄金海岸和柏林矽卡岩的形成。绢云母蚀变的悉尼Monzodiorite中石英黄铁矿-黄铜矿-辉钼矿脉中的辉钼矿的年龄为1.3166±0.0043 Ma，在黄金海岸矽卡岩下方的伊鲁（Ieru）粉砂岩中，石英黄铁矿-黄铜矿-辉钼矿脉的年龄为1.3031±0.0015 Ma。 0.0029和1.2078±0.0031 Ma。石英-钾长石-黄铁矿-辉钼矿脉中的辉钼矿年龄为1.2120±0.0024 Ma，其覆盖了悉尼蒙脱闪闪岩中的乙炔化蚀变。这些样品记录了宁基QMP及其周围和粉砂岩山脊的斑岩型矿化。来自富比兰QMP中热液侵入角砾岩基质的辉钼矿样品年龄为1.2146±0.0020 Ma，与相邻的粉砂岩矿化年龄相似，并被解释为在角砾岩形成过程中被机械地结合到了角砾岩中。Ok Tedi矿山中的侵入岩放置了大约200,000年，而Cu-Au矿化形成的持续时间要短得多。悉尼Monzodiorite和Ieru粉砂岩的黄金海岸矽卡岩及相关的斑岩型脉形成于14,000至21,000年（n = 3），粉砂岩斑岩系统于2,000至12,000年（n = 4）以及Fubilan斑岩系统31,000至40,000年（n = 6）。由于缺乏辉钼矿，塔拉纳基矽卡岩尚未在矿区过时，但地质关系表明它比富比兰QMP还年轻。000至21,000年（n = 3），粉砂岩斑岩系统在2,000至12,000年（n = 4），以及Fubilan斑岩系统在31,000至40,000年（n = 6）。由于缺乏辉钼矿，塔拉纳基矽卡岩尚未在矿区过时，但地质关系表明它比富比兰QMP还年轻。000至21,000年（n = 3），粉砂岩斑岩系统在2,000至12,000年（n = 4），以及Fubilan斑岩系统在31,000至40,000年（n = 6）。由于缺乏辉钼矿，塔拉纳基矽卡岩尚未在矿区过时，但地质关系表明它比富比兰QMP还年轻。