Abstract

The Northparkes district, central New South Wales, hosts several economic Cu–Au deposits associated with discrete, thin, porphyry intrusive complexes emplaced in the Late Ordovician during formation of the Macquarie Arc. The recently discovered Two-Thirty Cu–Au–(Mo) prospect is a mineralised magmatic–hydrothermal breccia complex that is hosted by the moderately east-dipping Goonumbla Volcanic Complex on the western limb of the Milpose Syncline ∼15 km south of the Northparkes porphyry district. Generation of the magmatic–hydrothermal breccia complex is interpreted to be related to the 448.0 ± 4.4 Ma emplacement of the Two-Thirty porphyry. However, Re–Os dating of molybdenite from the breccia complex indicates a potential for a ca 440 Ma mineralising event that has similar timing to economic porphyry mineralisation in the Northparkes district. The discovery of the Two-Thirty prospect has important implications for exploration in the Northparkes district and the broader Macquarie Arc. Two-Thirty is only the second known occurrence of magmatic-hydrothermal breccia-hosted mineralisation discovered within the Macquarie Arc, with the other being Cadia Quarry. Mineralisation at Two-Thirty is potentially older than the Northparkes and Cadia deposits, and younger than the epithermal and calc-alkaline deposits at Cowal, Marsden and Ridgeway.

1. KEY POINTS:

2. The Two-Thirty is a polyphase magmatic–hydrothermal breccia complex that hosts Cu–Au (Mo).

3. The Two-Thirty is the first significant breccia-hosted mineralisation found in the Northparkes district.

4. U–Pb zircon crystallisation ages of the causative intrusion at Two-Thirty pre-date mineralisation at Northparkes.

5. Re–Os dates of molybdenite from the Two-Thirty breccia complex are coeval with syn-mineralisation at Northparkes, supporting the model of periodic release of melts and fluids from underlying magma chambers during the formation of porphyry mineralisation in the Northparkes district.

摘要

新南威尔士州中部的Northparkes区拥有数个经济型Cu-Au矿床，这些矿床与麦格理弧形成期间奥陶纪晚期所形成的离散的，稀薄的斑岩侵入复合体有关。最近发现的二三十（Cu）-Au（-Mo）矿床是一个矿化岩浆-热液角砾岩复合体，由北向斑岩以南约15公里的Milpose Syncline西侧的适度向东倾入的Goonumbla火山复合体提供。区。岩浆-热液角砾岩复合体的产生被解释为与二三十年代斑岩的448.0±4.4 Ma位置有关。但是，角砾岩中辉钼矿的Re-Os年代表明了潜在的钙440 Ma矿化事件的发生时间与Northparkes地区的经济斑岩矿化时间相似。二三十年代的发现对Northparkes地区和更广阔的Macquarie Arc的勘探具有重要意义。麦格理弧线内发现的岩浆热液角砾岩成矿作用仅次于二十分，而另一处是卡迪亚采石场。二三十点的矿化作用可能比Northparkes和Cadia矿床要老，而比Cowal，Marsden和Ridgeway的超热和钙碱性矿床要年轻。

1. 关键点：

2. 二三十年代是一个多相岩浆-热液角砾岩复合体，其中含有Cu-Au（Mo）。

3. 二三十年代是在北帕克斯地区发现的第一个以角砾岩为主的重要矿化带。

4. 在Northparkes早二十点矿化时，致使侵入的U–Pb锆石结晶年龄。

5. 在北帕克斯地区，二三十年代角砾岩复合物中的辉钼矿的Re-Os年代与同矿化同时期，支持了北帕克斯地区斑岩矿化形成过程中从地下岩浆室周期性释放熔体和流体的模型。