A Laurentian cratonic reference from the distal Proterozoic basement of Western Newfoundland using tandem in situ and isotope dilution U-pb zircon and titanite geochronology

IF 1.9 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY American Journal of Science Pub Date : 2021-09-01 DOI:10.2475/07.2021.02
E. Hodgin, F. Macdonald, J. Crowley, M. Schmitz
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Abstract

The Humber Margin of Newfoundland preserves the most distal exposures of Proterozoic basement in northeastern Laurentia. Age uncertainty has permitted a range of hypotheses for its origin and links to subsequent tectonic events. One hypothesis has proposed large-scale orogen-parallel displacement between basement blocks in western Newfoundland. The apparent absence of Grenville- (∼1250–950 Ma sensu lato) or Taconic-aged (∼480–450 Ma) magmatism or metamorphism on the Corner Brook Lake Block (CBLB), which are defining features of the Humber Margin, has been reconciled by restoring the CBLB to a pre-Taconic position in Labrador with >400 km of post-Taconic dextral motion along the Humber River Fault. To test this model and better define the basement and Paleozoic rifted margin of North America, we conducted a geochronological study of the CBLB and the basement of the adjacent Humber Margin at Indian Head Range using tandem in situ and isotope dilution U-Pb zircon and titanite geochronology. These basement blocks, separated by the Humber River Fault, consist of ∼1500 and ∼1250 Ma protoliths, 1140 to 1135 Ma magmatism, 1000 to 970 Ma metamorphism, and ∼607 Ma intraplate magmatism. These basement blocks are also overlain by similar late Ediacaran to Cambrian siliciclastic successions with similar detrital zircon age spectra. From this set of geological data, we conclude that the Humber River Fault did not accommodate significant orogen-parallel displacement. New basement ages and a revised compilation of detrital zircon ages from overlying rift-related deposits contribute to a geochronologic cratonic reference datum for western Newfoundland's crystalline basement, whose protolith has a restricted age range from circa 1500 to 950 Ma. New age constraints for metasedimentary rocks are also used to document a 1250 to 1135 Ma succession at Indian Head Range and a ∼1000 Ma succession on the CBLB associated with Grenvillian orogenesis. Protracted late Grenvillian tectono-thermal events are inferred from cores and metamorphic overgrowths of ∼990 to 920 Ma detrital titanite in late Ediacaran conglomerate overlying CBLB basement.
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纽芬兰西部远元古代基底的劳伦克拉通参考,使用串联原位和同位素稀释U-pb锆石和钛矿地质年代学
纽芬兰的亨伯边缘保留了劳伦斯东北部最远的元古代基底暴露。年龄的不确定性允许对其起源以及与随后的构造事件的联系进行一系列假设。一种假说提出了纽芬兰西部基底块体之间的大规模造山带平行位移。Corner Brook Lake地块(CBLB)上明显不存在Grenville-(~1250–950 Ma,广义)或Taconic时效(~480–450 Ma)岩浆作用或变质作用,这是Humber边缘的决定性特征,通过将CBLB恢复到拉布拉多的Taconic前位置,沿着Humber河断层进行>400 km的Taconic-后右旋运动,可以调和这一点。为了测试该模型并更好地确定北美洲的基底和古生代裂谷边缘,我们使用串联原位和同位素稀释U-Pb锆石和钛酸盐地质年代学对印度洋岬山脉的CBLB和邻近亨伯边缘的基底进行了地质年代学研究。这些基底块体由亨伯河断层分隔,由~1500和~1250 Ma的原岩、1140至1135 Ma的岩浆作用、1000至970 Ma的变质作用和~607 Ma的板内岩浆作用组成。这些基底块体也覆盖着类似的晚埃迪卡拉纪至寒武纪硅化碎屑序列,具有类似的碎屑锆石年龄谱。根据这组地质数据,我们得出结论,亨伯河断层没有容纳显著的造山带平行位移。新的基底年龄和上覆裂谷相关矿床碎屑锆石年龄的修订汇编为纽芬兰西部结晶基底的地质年代克拉通参考基准做出了贡献,其原岩的年龄范围约为1500至950 Ma。变质沉积岩的新年龄限制也被用于记录印度头山脉1250至1135 Ma的层序,以及与格伦维尔造山运动相关的CBLB上的~1000 Ma层序。从覆盖CBLB基底的晚埃迪卡拉纪砾岩中~990至920Ma碎屑钛酸岩的岩芯和变质过度生长推断出长期的晚格伦维尔期构造热事件。
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来源期刊
American Journal of Science
American Journal of Science 地学-地球科学综合
CiteScore
5.80
自引率
3.40%
发文量
17
审稿时长
>12 weeks
期刊介绍: The American Journal of Science (AJS), founded in 1818 by Benjamin Silliman, is the oldest scientific journal in the United States that has been published continuously. The Journal is devoted to geology and related sciences and publishes articles from around the world presenting results of major research from all earth sciences. Readers are primarily earth scientists in academia and government institutions.
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