Early Neoproterozoic magmatism and Caledonian metamorphism recorded by the Mårma Terrane, Seve Nappe Complex, northern Swedish Caledonides

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of the Geological Society Pub Date : 2023-06-06 DOI:10.1144/jgs2022-092

R. Callegari, K. Kośmińska, C. Barnes, I. Klonowska, A. Barker, S. Rousku, E. Nääs, E. Kooijman, P. Witt-Nilsson, J. Majka

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Abstract

Petrology, geochronology, and bulk rock chemistry are combined to investigate the early Neoproterozoic magmatism and Cambrian-Ordovician metamorphism in the northern Swedish Caledonides. This includes several lithologies of the Mårma terrane in the Seve Nappe Complex exposed in the Kebnekaise region. U–Pb zircon geochronology yielded crystallization ages of 835 ± 8 Ma for a mylonitic orthogneiss, 864 ± 3 Ma for the Vistas Granite and 840 ± 7 Ma for a related granitic dyke. While a gabbro and granodiorite intrusions gave U–Pb zircon crystallization ages of 856 ± 3 Ma and 850 ± 1 Ma, respectively. U–Pb monazite dating of the mylonitic orthogneiss gave an upper intercept age of 841 ± 7 Ma and a lower intercept age of 443 ± 20 Ma. Pressure-temperature estimates derived for the mylonitic orthogneiss reveal metamorphic peak-pressure and peak-temperature of 10.5–11.75 kbar and 550–610 °C and 7.4–8.1 kbar at 615–675 ℃, respectively. Metamorphic pressure-temperature estimates for the Vistas Granite yield 6.5–7.5 kbar at 600–625 ℃. Whole rock chemistry coupled with U–Pb geochronology indicate that bimodal magmatism was related to attempted rifting of Rodinia between 870-840 Ma. Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle Supplementary material: https://doi.org/10.6084/m9.figshare.c.6675075

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瑞典喀里多尼亚北部Seve推覆杂岩mamatrma地体记录的新元古代早期岩浆作用与加里东期变质作用

将岩石学、地质年代学和大块岩石化学相结合，研究了瑞典喀里多尼亚山脉北部新元古代早期岩浆作用和寒武纪-奥陶纪变质作用。这包括Kebnekaise地区暴露的Seve Nappe杂岩中Mårma地体的几个岩性。U–Pb锆石地质年代学得出的糜棱岩正片麻岩结晶年龄为835±8 Ma，Vistas花岗岩结晶年龄为864±3 Ma，相关花岗岩脉结晶年龄为840±7 Ma。辉长岩和花岗闪长岩侵入体的U–Pb锆石结晶年龄分别为856±3 Ma和850±1 Ma。糜棱岩正片麻岩的U–Pb独居石测年给出了841±7Ma的上截距年龄和443±20Ma的下截距年龄。推导出的糜棱岩正片麻岩压力-温度估计值显示，在615–675℃下，变质峰值压力和峰值温度分别为10.5–11.75kbar、550–610°C和7.4–8.1kbar。Vistas花岗岩在600–625℃时的变质压力-温度估计值为6.5–7.5 kbar。全岩化学与U–Pb地质年代学相结合表明，双峰岩浆作用与870-840 Ma之间的罗迪尼亚裂谷作用有关。专题收藏：本文是Caledonian Wilson旋回收藏的一部分，可在：https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle补充材料：https://doi.org/10.6084/m9.figshare.c.6675075

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来源期刊

Journal of the Geological Society 地学-地球科学综合

CiteScore

6.00

自引率

3.70%

发文量

审稿时长

6-12 weeks

期刊介绍： Journal of the Geological Society (JGS) is owned and published by the Geological Society of London. JGS publishes topical, high-quality recent research across the full range of Earth Sciences. Papers are interdisciplinary in nature and emphasize the development of an understanding of fundamental geological processes. Broad interest articles that refer to regional studies, but which extend beyond their geographical context are also welcomed. Each year JGS presents the ‘JGS Early Career Award'' for papers published in the journal, which rewards the writing of well-written, exciting papers from early career geologists. The journal publishes research and invited review articles, discussion papers and thematic sets.