Geochronology (zircon U-Pb, Hf, O isotopes), provenance analysis, and tectonic setting of the Paleoproterozoic Karrat Group and supracrustal rocks of the Rinkian fold belt, West Greenland

IF 7.2 1区地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY Gondwana Research Pub Date : 2024-07-23 DOI:10.1016/j.gr.2024.07.011

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Abstract

We use zircon U-Pb, Hf and O isotopes to constrain the depositional ages and provenance of metasedimentary rocks of the Paleoproterozoic Karrat Group of West Greenland and to understand the tectonic processes leading to basin development on the eastern Rae craton. An older supracrustal assemblage (Qeqertarssuaq complex) deposited after ca. 2.6 Ga is separated by an unconformity with a younger supracrustal assemblage (the Karrat Group). The Qaarsukassak Formation at the base of the Karrat Group was deposited after ca. 2.0 Ga, with dominantly Archean age modes. The youngest siliciclastic rocks (Nûkavsak and Mârmorilik formations) in the Karrat Group have maximum depositional ages ranging from ca. 1980 to 1950 to 1900 Ma and contain dominant detrital zircon age modes between ca. 2.50 and 1.93 Ga. A ca. 1.92 Ga supracrustal assemblage referred to as the northern domain (Karrat Group, sensu lato) is geographically separated from the Karrat Group (sensu stricto) by the Prøven igneous complex. The stratigraphy and detrital zircon profiles are compared to broadly coeval sedimentary units on the Rae craton and a unifying model of their deposition is presented. The Rae craton is the dominant detritus source; initially these sources were mostly local, changing to a mix of local and distal sources including the western Rae craton. The tectonic setting of the Karrat basin transitioned from extensional to convergent to collisional during its basin evolution, reflecting Wilson cycle phases within an epeiric sea. Accordingly, zircon Hf isotopes in our dataset track the evolution of the opening and closing of the Manikewan Ocean. Detrital zircon Hf isotopes in our dataset reveal a greater proportion of juvenile detritus (especially ca. 2.15–1.95 Ga) than is known from the currently exposed crustal record, pointing to the importance of the detrital zircon record for understanding Paleoproterozoic crustal and tectonic evolution.

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格陵兰西部旧新生代卡拉特组和林肯褶皱带上壳岩的地质年代（锆石U-Pb、Hf、O同位素）、产状分析和构造环境

我们利用锆石 U-Pb、Hf 和 O 同位素来确定格陵兰西部古新生代卡拉特群的沉积年龄和成因，并了解导致东部雷伊克拉通盆地发展的构造过程。约 2.6 Ga 后沉积的一个较古老的超地壳组合（Qeqertarssuaq 复合体）被一个由侏罗纪火山岩组成的岩浆岩带所分隔。2.6Ga之后沉积下来的较古老的超地壳组合（Qeqertarssuaq复合体）与较年轻的超地壳组合（卡拉特群）之间存在一个不整合层理。卡拉特组底部的Qaarsukassak地层沉积于约2.0 Ga之后。2.0Ga之后沉积，主要为阿寒纪年龄模式。卡拉特群最年轻的硅质碎屑岩（努卡夫萨克地层和马莫瑞里克地层）的最大沉积年龄介于约1980至1950至1900Ma之间，主要的锆英石年龄模式介于约2.50至1.93Ga之间。一个约 1.92 Ga 的超地壳组合被称为北域（卡拉特组，sensu lato），在地理上被普罗文火成岩复合体与卡拉特组（sensu stricto）分隔开来。地层学和锆英石剖面与瑞伊克拉通上大致同时期的沉积单元进行了比较，并提出了一个统一的沉积模型。雷伊克拉通是主要的碎屑源；最初这些碎屑源主要来自当地，后来转变为当地和远端碎屑源的混合，包括雷伊克拉通西部。卡拉特海盆的构造环境在其海盆演化过程中从伸展型过渡到收敛型，再到碰撞型，反映了一个peiric海中的威尔逊循环阶段。因此，我们数据集中的锆石Hf同位素追踪了马尼基万洋的开合演化过程。我们数据集中的碎屑锆石 Hf 同位素揭示出的幼年碎屑（尤其是约 2.15-1.95 Ga）所占比例大于目前出露地壳记录中已知的比例，这表明碎屑锆石记录对于了解古近纪地壳和构造演化的重要性。

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来源期刊

Gondwana Research 地学-地球科学综合

CiteScore

12.90

自引率

6.60%

发文量

298

审稿时长

65 days

期刊介绍： Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.