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U-Pb geochronology, geochemistry, and isotopic composition of granitoids across the Nolan-Zemlak domain boundary in the SW Rae craton, Laurentia: Evidence for a late Neoarchean suture reworked during Arrowsmith orogen
Precambrian Research ( IF 3.2 ) Pub Date : 2021-07-28 , DOI: 10.1016/j.precamres.2021.106303
M.A. Cloutier 1 , K.M. Bethune 1 , K.E. Ashton 2 , J.M.K. Deane 1
Affiliation  

The Nolan-Zemlak domain boundary in the southwestern Rae Province separates ca. 2.6 Ga granodioritic to granitic rocks (Nolan suite) of the Nolan lithotectonic domain to the north from an assemblage of ca. 2.52 Ga ultramafic-intermediate plutonic rocks (Zemlak suite) and ca. 2.3 Ga granitoids, and derived gneisses, of the Zemlak domain to the south, the latter representing part of the Taltson basement complex (TBC). The restriction of the Zemlak suite to south of the domain boundary suggests that its emplacement was structurally controlled, an inference supported by recognition of pre-2.52 Ga deformation in Nolan domain. This paper reports the results of U-Pb and Lu-Hf isotopic analysis of zircon, coupled with multi-element whole-rock geochemical analysis, for the Nolan and Zemlak suites, plus a younger suite of leucogranites that stitch the domain boundary. Both the Nolan and Zemlak suites have geochemical-isotopic signatures consistent with subduction-related magmatism, but the ca. 2.52 Ga Zemlak suite is distinguished by anomalously low Th concentrations, attributed to minimal sediment flux into the mantle wedge. Zircon rims from Nolan granites record ca. 2.52 Ga metamorphism ascribed to intrusion of the Zemlak suite. Regionally, these observations are best explained by the subduction-related accretion of the Zemlak terrane, part of a larger Paleo-Mesoarchean crustal block now embedded within the TBC, to a ‘proto-Rae’ cratonic core. A model is presented wherein circa 2.64–2.58 Ga (Nolan age) continental arc magmatism was generated via north-dipping subduction below the proto-Rae craton leading to eventual collision/accretion of the outboard Paleo-Mesoarchean block. Collisional suturing occurred by ca. 2.57 Ga, as recorded by both local and regional metamorphic ages. Following collision, subduction is inferred to have stepped outward, directed beneath the now amalgamated Nolan and Paleo-Mesoarchean (Zemlak/TBC) terrane with further arc magmatism represented by the ca. 2.52 Ga Zemlak suite. Thereafter, arc magmatism continued along the west-southwest margin of Rae craton from ca. 2.47 Ga to 2.4 Ga, likely the expression of Arrowsmith orogeny. Terminal collision ending the Arrowsmith orogenic cycle resulted in reactivation of the boundary zone and formation of the South Tazin Lake shear zone coeval with 2.37 Ga metamorphism and leucogranite emplacement.



中文翻译:

U-Pb 年代学、地球化学和横跨西南 Rae 克拉通、Laurentia 的 Nolan-Zemlak 域边界的花岗岩的同位素组成:Arrowsmith 造山带重新加工的新太古代晚期缝合线的证据

Rae省西南部的Nolan-Zemlak域边界将约。2.6 Ga 花岗闪长岩到花岗岩(Nolan 组)的 Nolan 岩石构造域,从约 2.52 Ga 超镁铁质-中质深成岩(Zemlak 岩套)和约。2.3 南部泽姆拉克域的 Ga 花岗岩和衍生片麻岩,后者代表了塔尔森基底复合体 (TBC) 的一部分。Zemlak 套件对域边界以南的限制表明其就位受到结构控制,这一推论得到了对诺兰域中 2.52 Ga 前变形的识别的支持。本文报告了对 Nolan 和 Zemlak 套件进行的锆石 U-Pb 和 Lu-Hf 同位素分析以及多元素全岩地球化学分析的结果,加上一组较新的白花岗岩,它们缝合了域边界。Nolan 和 Zemlak 套件都具有与俯冲相关岩浆作用一致的地球化学同位素特征,但大约 2.52 Ga Zemlak 组以异常低的 Th 浓度为特征,这归因于进入地幔楔的最小沉积物通量。诺兰花岗岩的锆石边缘记录约。2.52 Ga 变质作用归因于 Zemlak 岩套的侵入。在区域上,这些观察结果最好通过 Zemlak 地体的俯冲相关增生来解释,该地体是一个更大的古中太古代地壳块的一部分,现在嵌入 TBC 中,到“原始 Rae”克拉通核心。提出了一个模型,其中大约 2.64-2。58 Ga(诺兰时代)大陆弧岩浆作用是通过原始 Rae 克拉通下方的北倾俯冲产生的,最终导致外侧古中太古代块体的碰撞/增生。碰撞缝合发生在大约。2.57 Ga,由当地和区域变质时代记录。碰撞后,推断俯冲已经向外展开,指向现在合并的诺兰和古中太古代(泽姆拉克/TBC)地体下方,具有进一步的弧岩浆作用,由约 . 2.52 Ga Zemlak 套房。此后,弧岩浆作用从大约 10 年代开始沿着 Rae 克拉通的西南偏西边缘继续发生。2.47 Ga 到 2.4 Ga,可能是阿罗史密斯造山运动的表现。结束阿罗史密斯造山循环的最终碰撞导致边界带的重新激活和南塔津湖剪切带的形成与 2.

更新日期:2021-07-28
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