New geochronological and geochemical data for the barren and ore-associated suites from the Northparkes porphyry Cu-Au deposits, Australia, have implications for magma fertility. The Goonumbla and Wombin Volcanics and intrusions are barren in the Northparkes area. A sample from Wombin suite yielded a zircon U-Pb age of 433.8 ± 3.1 Ma, whereas the ore-associated porphyries yielded ages between 441.8 ± 3.7 and 436.3 ± 4.5 Ma. The bulk of the mineralization at Northparkes is associated with a K-feldspar-phyric quartz monzonite porphyry (K-QMP), which gave U-Pb zircon ages of 441.8 ± 3.7 and 441.1 ± 2.5 Ma. Whole-rock Sr-Nd isotope compositions of the Goonumbla, Wombin, and ore-associated suites are similar, with (⁸⁷Sr/⁸⁶Sr)_i = 0.704112 to 0.704424 and ε_Nd = 5.6 to 6.9, which is typical of primitive intraoceanic island arcs, and their Pb isotope values lie within the MORB array. Most of the zircons from the Wombin and ore-associated suites have arc mantle-like O-Hf isotope compositions, with δ¹⁸O values that vary from 6.13 to 4.95, and ε_Hf(t) from 11.5 to 6. These results suggest that the Goonumbla, Wombin, and ore-associated suites originated from typical arc mantle. The magmas that produced the Goonumbla and Wombin suites were dominated by plagioclase-pyroxene fractionation, and the Wombin suite has a low oxidation state with ΔFMQ between ~0 and 1.5. They were relatively reduced and dry. This combination resulted in early sulfide saturation, probably without reaching fluid saturation. Trace element modeling shows that plagioclase-amphibole dominated the later stages of fractionation of the ore-associated suite, implying that it had a higher water content than the barren suites. It was also more oxidized (ΔFMQ from ~0 to 4). The result was late sulfide saturation, which was followed shortly thereafter by voluminous fluid release. As a consequence, the ore-forming fluid effectively transferred Cu and Au from the magma to the site of hydrothermal ore deposition. We suggest that the higher water content and oxidation state of the ore-associated suite was due to the deep underlying magma chamber, which was recharged by many more pulses of magma than the chamber that underlay the barren suites. This is more effective in raising the concentration of incompatible water and ferric iron in the residual melt than straight fractional crystallization. High oxygen fugacities and water contents played a significant role in determining the timing of sulfide and fluid saturation, respectively, and as a result, they had a critical influence on magma fertility.

中文翻译：

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澳大利亚新南威尔士州 Northparkes Igneous Suite 的年代学、岩石成因和氧化状态：对岩浆生育力的影响

来自澳大利亚 Northparkes 斑岩铜金矿床的贫瘠和与矿石相关的套房的新地质年代学和地球化学数据对岩浆的富集性有影响。Goonumbla 和 Wombin 火山和侵入体在 Northparkes 地区是贫瘠的。来自 Wombin 套件的样品产生了 433.8 ± 3.1 Ma 的锆石 U-Pb 年龄，而与矿石伴生的斑岩产生的年龄介于 441.8 ± 3.7 和 436.3 ± 4.5 Ma 之间。Northparkes 的大部分矿化与钾长石-岩质石英二长斑岩 (K-QMP) 相关，这使 U-Pb 锆石年龄分别为 441.8 ± 3.7 和 441.1 ± 2.5 Ma。Goonumbla、Wombin 和矿石伴生套件的全岩 Sr-Nd 同位素组成相似，( ⁸⁷ Sr/ ⁸⁶ Sr) _i = 0.704112 至 0.704424 和 ε_Nd = 5.6 到 6.9，这是原始洋内岛弧的典型特征，其 Pb 同位素值位于 MORB 阵列内。来自 Wombin 和矿石伴生套件的大多数锆石具有类似弧幔的 O-Hf 同位素组成，δ ¹⁸ O 值从 6.13 到 4.95 不等，ε _Hf(t)从 11.5 到 6。这些结果表明 Goonumbla、Wombin 和与矿石相关的套件起源于典型的弧形地幔。产生 Goonumbla 和 Wombin 套件的岩浆以斜长石-辉石分馏为主，Wombin 套件具有低氧化态，ΔFMQ 介于 ~0 和 1.5 之间。它们相对减少和干燥。这种组合导致早期硫化物饱和，可能没有达到流体饱和度。微量元素模型显示斜长石-角闪石在矿石伴生岩套的后期分馏阶段占主导地位，这意味着它比贫瘠岩套具有更高的含水量。它也被更多地氧化（ΔFMQ 从~0 到 4）。结果是晚期硫化物饱和，随后不久大量流体释放。作为结果，成矿流体有效地将铜和金从岩浆中转移到热液矿床的位置。我们认为，与矿石伴生的岩浆层较高的水含量和氧化态是由于下伏岩浆房较深，与位于贫瘠岩层之下的岩浆房相比，岩浆房被更多的岩浆脉冲补充。这在提高残余熔体中不相容的水和三价铁的浓度方面比直接分级结晶更有效。高氧逸度和含水量分别在确定硫化物和流体饱和的时间方面发挥了重要作用，因此，它们对岩浆的肥力产生了关键影响。我们认为，与矿石伴生的岩浆层较高的水含量和氧化态是由于下伏岩浆房较深，与位于贫瘠岩层之下的岩浆房相比，岩浆房被更多的岩浆脉冲补充。这在提高残余熔体中不相容的水和三价铁的浓度方面比直接分级结晶更有效。高氧逸度和含水量分别在确定硫化物和流体饱和的时间方面发挥了重要作用，因此，它们对岩浆的肥力产生了关键影响。我们认为，与矿石伴生的岩浆层较高的水含量和氧化态是由于下伏岩浆房较深，与位于贫瘠岩层之下的岩浆房相比，岩浆房被更多的岩浆脉冲补充。这在提高残余熔体中不相容的水和三价铁的浓度方面比直接分级结晶更有效。高氧逸度和含水量分别在确定硫化物和流体饱和的时间方面发挥了重要作用，因此，它们对岩浆的肥力产生了关键影响。这在提高残余熔体中不相容的水和三价铁的浓度方面比直接分级结晶更有效。高氧逸度和含水量分别在确定硫化物和流体饱和的时间方面发挥了重要作用，因此，它们对岩浆的肥力产生了关键影响。这在提高残余熔体中不相容的水和三价铁的浓度方面比直接分级结晶更有效。高氧逸度和含水量分别在确定硫化物和流体饱和的时间方面发挥了重要作用，因此，它们对岩浆的肥力产生了关键影响。