Kimberlites and related rocks are the focus of research and exploration in the Alto Paranaiba Igneous Province (APIP; Brazil) due to their potential correlation with adjacent diamond fields. New U-Pb perovskite ages were obtained using recommended protocols for error propagation and data interpretation. Despite the utility of perovskites for dating, their incorporation of significant common-Pb (common-Pb of new APIP data: 52–84 % for analyses, 75–95 % for TIMS concentrate analyses) limits the age resolution of this dating approach. Consequently, the APIP U-Pb ages neither confirm nor discredit previously proposed geodynamic models that invoke age progression or distinct magmatic episodes. Comparing the new ID-TIMS and LA-ICP-MS ages of the same intrusions, the LA-ICP-MS data have lower uncertainties, largely due to accessing a greater spread in common-Pb, improving regressions, and tend to yield older ages. For perovskite grains collected from weathering profiles, we found evidence of Pb-loss. This process leads to higher uncertainties in individual analyses, increased data scatter, and consequently higher uncertainties in age estimates. For fresh samples with different degrees of crustal contamination from a single intrusion, we found an indication of some variability in Pb/Pb and U/Pb ratios of the perovskite data, with a tendency towards older ages for more contaminated sample. For almost fresh intrusions with geochemically and isotopically similar mantle sources, related to the same event and in a close geographic area, we prefer to use a unique local Pb/Pb ratio as anchoring for each Tera-Wasserburg plot. This approach is particularly preferred when perovskite data of an intrusion are too clustered and the Pb/Pb ratio from the unanchored T-W differs from that predicted from theoretical Pb-isotope evolution model. Despite the high-common Pb in APIP perovskite crystals, our new data using these strategies clearly indicate that APIP magmatism is restricted to the Cretaceous, with most cases crystallized in Upper Cretaceous, but some from Early Cretaceous, such as the diamondiferous occurrence of Catalão-1b (120.6 ± 6.7 Ma). Different triggers of APIP magmatism are related to both episodes, mainly attributed to supercontinent break-up stages.

中文翻译：

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稳健的方法，棘手的材料：测定白垩纪巴西金伯利岩中高普通铅钙钛矿的挑战


由于金伯利岩和相关岩石与邻近钻石矿场存在潜在相关性，因此成为上巴拉那伊巴火成岩省（APIP；巴西）研究和勘探的重点。使用推荐的误差传播和数据解释协议获得了新的 U-Pb 钙钛矿年龄。尽管钙钛矿可用于测年，但它们掺入了大量的普通铅（新 APIP 数据的普通铅：52-84% 用于分析，75-95% 用于 TIMS 浓缩分析）限制了这种测年方法的年龄分辨率。因此，APIP U-Pb 年龄既不能证实也不能否定先前提出的引用年龄进展或不同岩浆事件的地球动力学模型。比较相同入侵的新 ID-TIMS 和 LA-ICP-MS 年龄，LA-ICP-MS 数据具有较低的不确定性，这主要是由于获得了更大范围的普通 Pb，改善了回归，并且往往会产生较旧的年龄。对于从风化剖面中收集的钙钛矿颗粒，我们发现了铅损失的证据。这一过程导致个体分析的不确定性增加、数据分散性增加，从而导致年龄估计的不确定性增加。对于单次侵入造成的不同程度地壳污染的新鲜样品，我们发现钙钛矿数据的 Pb/Pb 和 U/Pb 比率存在一些变化，污染程度较高的样品有年龄较大的趋势。对于地球化学和同位素相似的地幔源、与同一事件相关且地理区域相近的几乎新鲜的侵入体，我们更喜欢使用独特的当地 Pb/Pb 比率作为每个 Tera-Wasserburg 地块的锚定。 当侵入的钙钛矿数据过于聚集并且来自非锚定TW的Pb/Pb比与理论Pb同位素演化模型预测的不同时，这种方法是特别优选的。尽管 APIP 钙钛矿晶体中的 Pb 含量很高，但我们使用这些策略的新数据清楚地表明 APIP 岩浆作用仅限于白垩纪，大多数情况下在上白垩纪结晶，但也有一些来自早白垩世，例如 Catalão- 的含金刚石矿点。 1b（120.6±6.7Ma）。 APIP 岩浆活动的不同触发因素与这两个事件有关，主要归因于超大陆分裂阶段。