Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes
Geology and evolution of pegmatite-hosted U-Th ± REE-Y-Nb Mineralization, Kulyk, Eagle, and Karin Lakes region, Wollaston Domain, northern Saskatchewan, Canada: examples of the dual role of extreme fractionation and hybridization processes
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DOI：
10.3190/jgeosci.153
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发表时间：
2013-12
影响因子：
1.4
通讯作者：
Michelle McKeough;D. Lentz;C. McFarlane;J. Brown
中科院分区：
文献类型：
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作者：
Michelle McKeough;D. Lentz;C. McFarlane;J. Brown
*Corr responding author在萨斯喀彻温省北方，花岗伟晶岩侵入早古元古代沃拉斯顿群变质沉积岩和不整合地覆盖在晚太古代片麻岩上的交错褶皱花岗岩类，所有这些都在漫长的1.86至1.77 Ga Trans-Hudson造山运动期间受到变形。Wollaston域的Kulyk湖、鹰湖和Karin湖的产状以U-Th ± REE-Y-Nb伟晶岩侵入体和铀控制的铀矿化为特征。伟晶岩是中等到高度演化的，从矿物学上简单到复杂的类型。这些都是稀土元素类，NYF伟晶岩（Nb-Y-F），并解释为已形成在一个晚同碰撞后的构造环境。杂岩型伟晶岩由于与寄主岩石的交代作用而混杂，因此局部呈粗分带。U-Th ± REE-Y-Nb的饱和发生在混杂伟晶岩的边缘（主要是边带和壁带）。部分熔体产生在深度，然后合并，因为它们侵入到更高的结构水平在这个造山带的折返。这与这些花岗伟晶岩的U-Pb年代学相一致，它将它们限制在跨哈德逊造山运动的峰期和晚变质事件之间。年龄限制和相对高T部分熔融条件（~750 °C）将伟晶岩熔融形成条件限制在早期变形事件（1835-1805 Ma），该事件在c. 1770年。现场关系，结构和地球化学变化提供了强有力的证据表明，U，Th，REE ± Y-Nb阶段在所研究的伟晶岩是通过极端分馏效应，这是明显的，在整个多个伟晶岩注入逐步富集。此外，在伟晶岩熔体与围岩的复杂混杂反应过程中，挥发分等助熔组分进一步富集了U、Th、REE ± Y-Nb，直至伟晶岩侵位的最后阶段。
*Corr esponding author In northern Saskatchewan, granitic pegmatites intruded Early Paleoproterozoic Wollaston Group metasedimentary rocks and interfolded granitoids that unconformably overlie Late Archean gneisses, all of which have been subjected to deformation during the protracted 1.86 to 1.77 Ga Trans-Hudson Orogeny. The U–Th ± REE–Y–Nb pegmatite intrusions and fracture-controlled U mineralization characterize the occurrences at Kulyk Lake, Eagle Lake, and Karin Lake properties in the Wollaston Domain. The pegmatites are moderately to highly evolved, ranging from mineralogically simple to complex types. These are rare-earth element class, NYF pegmatites (Nb–Y–F), and are interpreted to have formed in a late syn- to post-collisional tectonic setting. The complex-type pegmatites are hybridized, due to metasomatic interaction with the host rocks and therefore are locally crudely zoned. Saturation of U–Th ± REE–Y–Nb occurred at the margins (predominately the border and wall zones) of the hybridized pegmatites. Partial melts were generated at depth, and then coalesced as they intruded to higher structural levels during exhumation of this orogen. This agrees with U–Pb geochronology of these granitic pegmatites, which constrains them between peak- and late-metamorphic events of the Trans-Hudson Orogeny. The age constraints and relatively high-T partial melting conditions (~750 °C) confine the pegmatite melt-forming conditions to an early deformational event (1835–1805 Ma) that was overprinted by high-T retrograde metamorphism at c. 1770 Ma. Field relationships, textures and geochemical variations provide strong evidence that the U, Th, REE ± Y– Nb phases in the studied pegmatites were progressively enriched through extreme fractionation effects of which are evident throughout multiple pegmatite injections. In addition, volatiles and other fluxing components further enriched U, Th, REE ± Y– Nb during complex hybridization reactions between pegmatite melt and wallrock, up to the final stages of pegmatite emplacement.