Since the second half of the twentieth century, exotic copper mineralization represents a prime target for many mining exploration companies operating in the hyperarid Atacama Desert, in northern Chile. Although there is evidence that the emplacement of such deposits took place during specific Tertiary climatic periods and relief formation, many uncertainties remain regarding the exact timing for their deposition and/or the genetic link between the exotic deposits and the primary porphyry copper deposits. We present a first attempt of U-Pb dating of copper-rich minerals from the Mina Sur exotic deposit from the Chuquicamata mining district. A suite of Mn-rich black chrysocolla clasts surrounded by pseudomalachite bands has been characterized and dated in petrographic context using both nanosecond and femtosecond in situ laser ablation ICP-MS analyses. U-Pb dating on pseudomalachite bands yields a crystallization age of 18.4 ± 1.0 Ma. For the Mn-rich chrysocolla clasts, the 206 Pb/ 238 U apparent ages range from 19.7 ± 5.0 Ma to 6.1 ± 0.3 Ma, a spread interpreted as the result of U and/or Pb mobility linked to fluid circulation following crystallization. This study demonstrates that supergene copper mineralization can be directly dated by the U-Th-Pb method on pseudomalachite. Furthermore, the age obtained on pseudomalachite indicates that Mina Sur copper deposition took place at ca. 19 Ma, about 11 m.y. after the unroofing and hydrothermal alteration of the Chuquicamata deposit, a result that is consistent with the supergene ages already known in the Atacama Desert.

中文翻译：

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表生铜矿化的首次 U-Pb LA-ICP-MS 原位测年：以智利阿塔卡马沙漠 Chuquicamata 矿区为例

自 20 世纪下半叶以来，奇异的铜矿化成为许多在智利北部极度干旱的阿塔卡马沙漠中经营的矿业勘探公司的主要目标。尽管有证据表明此类矿床的就位发生在特定的第三纪气候时期和地势形成期间，但关于其沉积的确切时间和/或外来矿床与原生斑岩铜矿床之间的遗传联系仍存在许多不确定性。我们首次尝试对来自 Chuquicamata 矿区的 Mina Sur 奇异矿床中的富铜矿物进行 U-Pb 测年。使用纳秒和飞秒原位激光烧蚀 ICP-MS 分析对一组被假孔雀石带包围的富含锰的黑色金玉藻碎屑进行了表征并在岩相学背景下确定了年代。假孔雀石带上的 U-Pb 测年产生 18.4 ± 1.0 Ma 的结晶年龄。对于富含锰的金球藻碎屑，206 Pb/238 U 的表观年龄范围从 19.7 ± 5.0 Ma 到 6.1 ± 0.3 Ma，这种扩散被解释为与结晶后流体循环相关的 U 和/或 Pb 迁移率的结果。本研究表明，利用 U-Th-Pb 法可以直接对假孔雀石进行表生铜矿化测年。此外，在假孔雀石上获得的年龄表明 Mina Sur 铜沉积发生在大约 19 Ma，在 Chuquicamata 矿床开顶和热液蚀变后约 11 my，