New U–Pb age and Hf isotope data obtained on detrital zircon grains from Au- and U-bearing Archaean quartz-pebble conglomerates in the Singhbhum Craton, eastern India, specifically the Upper Iron Ore Group in the Badampahar Greenstone Belt and the Phuljhari Formation below the Dhanjori Group provide insights into the zircon provenance and maximum age of sediment deposition. The most concordant, least disturbed ²⁰⁷Pb/²⁰⁶Pb ages cover the entire range of known magmatic and higher grade metamorphic events in the craton from 3.48 to 3.06 Ga and show a broad maximum between 3.38 and 3.18 Ga. This overlap is also mimicked by Lu–Hf isotope analyses, which returned a wide range in ε_Hf(t) values from + 6 to − 5, in agreement with the range known from zircon grains in igneous and metamorphic rocks in the Singhbhum Craton. A smaller but distinct age peak centred at 3.06 Ga corresponds to the age of the last major magmatic intrusive event, the emplacement of the Mayurbhanj Granite and associated gabbro, picrite and anorthosite. Thus, these intrusive rocks must form a basement rather than being intrusive into the studied conglomerates as previously interpreted. The corresponding detrital zircon grains all have a subchondritic Hf isotopic composition. The youngest reliable zircon ages of 3.03 Ga in the case of the basal Upper Iron Ore Group in the east of the craton and 3.00 Ga for the Phuljhari Formation set an upper limit on the age of conglomerate sedimentation. Previously published detrital zircon age data from similarly Au-bearing conglomerates in the Mahagiri Quartzite in the Upper Iron Ore Group in the south of the craton gave a somewhat younger maximum age of sedimentation of 2.91 Ga. There, the lower limit on sedimentation is given by an intrusive relationship with a c. 2.8 Ga granite. The time window thus defined for conglomerate deposition on the Singhbhum Craton is almost identical to the age span established for the, in places, Au- and U-rich conglomerates in the Kaapvaal Craton of South Africa: the 2.98–2.78 Ga Dominion Group and Witwatersrand Supergroup in South Africa. Since the recognition of first major concentration of gold on Earth’s surface by microbial activity having taken place at around 2.9 Ga, independent of the nature of the hinterland, the above similarity in age substantially increases the potential for discovering Witwatersrand-type gold and/or uranium deposits on the Singhbhum Craton. Further age constraints are needed there, however, to distinguish between supposedly less fertile (with respect to Au) > 2.9 Ga and more fertile < 2.9 Ga successions.

从印度东部 Singhbhum 克拉通的含金和含 U 的太古代石英卵石砾岩，特别是巴丹帕哈绿岩带的上铁矿石群和下方的 Puljhari 组中获得的碎屑锆石颗粒的新 U-Pb 年龄和 Hf 同位素数据Dhanjori Group 提供了有关锆石来源和沉积物沉积最大年龄的见解。最一致、干扰最小的²⁰⁷ Pb/ ²⁰⁶ Pb 年龄涵盖了克拉通 3.48 至 3.06 Ga 的整个已知岩浆和更高级变质事件范围，并显示出 3.38 至 3.18 Ga 之间的广泛最大值。Lu 也模仿了这种重叠–Hf 同位素分析，返回的 ε _{Hf范围很广}(t) 值从 + 6 到 - 5，与 Singhbhum 克拉通火成岩和变质岩中的锆石颗粒已知的范围一致。一个以 3.06 Ga 为中心的较小但明显的年龄峰对应于最后一次主要岩浆侵入事件的年龄，即 Mayurbhanj 花岗岩和相关辉长岩、苦橄榄石和斜长岩的侵位。因此，这些侵入岩必须形成基底，而不是像先前解释的那样侵入所研究的砾岩。相应的碎屑锆石颗粒均具有亚球粒状 Hf 同位素组成。克拉通东部基底上铁矿群的最年轻可靠锆石年龄为 3.03 Ga，Phuljhari 组为 3.00 Ga，确定了砾岩沉积年龄的上限。先前发表的来自克拉通南部上铁矿石群的 Mahagiri 石英岩中类似的含金砾岩的碎屑锆石年龄数据给出了 2.91 Ga 的较年轻的最大沉积年龄。在那里，沉积的下限由下式给出与 c 的侵入性关系。2.8 Ga 花岗岩。因此为 Singhbhum 克拉通砾岩沉积定义的时间窗口几乎与为南非 Kaapvaal 克拉通富含金和铀的砾岩确定的年龄跨度：2.98–2.78 Ga Dominion Group 和 Witwatersrand南非的超级集团。由于在 2.9 Ga 左右发生了微生物活动，在地球表面发现了第一个主要的黄金浓度，与腹地的性质无关，上述年龄相似性大大增加了在 Singhbhum 克拉通发现威特沃特斯兰德型金和/或铀矿床的潜力。然而，那里需要进一步的年龄限制，以区分所谓的肥沃（相对于金）> 2.9 Ga 和更多肥沃的 < 2.9 Ga 演替。