Abstract Neoproterozoic Li–Cs–Ta (LCT) pegmatites and pegmatitic sheeted leucogranites (SLGs) of the Damara Belt, Namibia, although coeval, are variably mineralized and have intruded multiple tectono-stratigraphic units. Major and trace element data together with oxygen and hydrogen isotopes were used to identify possible sources for these pegmatite melts. Two groups of pegmatites can be identified on the basis of O-isotopes. Group A pegmatites, which include U-enriched pegmatitic SLGs with a Nb–Y–F (NYF) pegmatite affinity ( Kinnaird and Nex, 2007 ), and Li–Be-rich LCT pegmatites, with δ18O = 11.2–12.9‰, are metaluminous to peraluminous, suggesting that they evolved from a partial melt of a mixed metasedimentary and igneous source. Group B pegmatites, which contain Sn, Li–Sn and tourmaline mineralization, have higher δ18O values (14–16‰), consistent with their derivation from a purely S-type source, with possible incorporation of, or exchange with, carbonates. Crystallization temperatures calculated using Ti-in-quartz and O-isotope thermometry are in agreement with each other, and range from 420 to 575 °C for LCT pegmatites and 650 °C for pegmatitic SLGs. The juxtaposition of coeval, post-tectonic LCT pegmatites and pegmatitic SLGs with an NYF affinity in the Damara Belt precludes tectonic setting as the only source of compositional variability in LCT and NYF pegmatite melts.

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稀有元素矿化达马拉带伟晶岩的起源：地球化学和光稳定同位素研究

摘要 纳米比亚达马拉带的新元古代 Li-Cs-Ta (LCT) 伟晶岩和伟晶质片状白质花岗岩 (SLGs) 虽然是同一时期，但矿化程度不一，并侵入了多个构造地层单元。主要和痕量元素数据以及氧和氢同位素被用来确定这些伟晶岩熔体的可能来源。可以根据 O 同位素确定两组伟晶岩。A 组伟晶岩，包括具有 Nb-Y-F (NYF) 伟晶岩亲和性的富含 U 的伟晶岩 SLG（Kinnaird 和 Nex，2007 年）和富含 Li-Be 的 LCT 伟晶岩，δ18O = 11.2-12.9‰，是金属铝质的到过铝质，表明它们是由变沉积岩和火成岩混合源的部分熔融演化而来的。B 组伟晶岩，含有 Sn、Li-Sn 和电气石矿化，具有较高的 δ18O 值（14-16‰），与它们源自纯 S 型来源一致，可能与碳酸盐结合或交换。使用石英中钛和 O 同位素温度计计算的结晶温度彼此一致，LCT 伟晶岩的结晶温度范围为 420 至 575 °C，伟晶岩 SLG 的结晶温度范围为 650 °C。Damara 带中同时期的、后构造 LCT 伟晶岩和伟晶质 SLG 并列具有 NYF 亲和力，排除了构造环境作为 LCT 和 NYF 伟晶岩熔体成分变化的唯一来源。LCT 伟晶岩的温度范围为 420 至 575 °C，伟晶岩 SLG 的温度范围为 650 °C。Damara 带中同时期的、后构造 LCT 伟晶岩和伟晶质 SLG 并列具有 NYF 亲和力，排除了构造环境作为 LCT 和 NYF 伟晶岩熔体成分变化的唯一来源。LCT 伟晶岩的温度范围为 420 至 575 °C，伟晶岩 SLG 的温度范围为 650 °C。Damara 带中同时期的、后构造 LCT 伟晶岩和伟晶质 SLG 并列具有 NYF 亲和力，排除了构造环境作为 LCT 和 NYF 伟晶岩熔体成分变化的唯一来源。