U-Pb isotopic ages of euhedral zircons in the Rhaetian of British Columbia: Implications for Cordilleran tectonics during the Late Triassic
U-Pb isotopic ages of euhedral zircons in the Rhaetian of British Columbia: Implications for Cordilleran tectonics during the Late Triassic
复制标题
不列颠哥伦比亚雷蒂亚地区自形锆石的 U-Pb 同位素年龄：对晚三叠世科迪勒拉构造的影响
DOI：
10.1130/ges01324.1
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发表时间：
2016
期刊：
影响因子：
2.5
通讯作者：
M. Orchard
中科院分区：
文献类型：
--
作者：
M. Golding;J. Mortensen;J. Zonneveld;M. Orchard
从保存在不列颠哥伦比亚省东北部黑熊岭剖面的Rhaetian地层中发现的正面体第一旋回锆石颗粒中获得了新的同位素年龄。有两个具有统计学意义的种群存在：老年种群约为224 Ma，而占主导地位的年轻种群约为205 Ma。年轻组包括一组颗粒，其206Pb/238U加权平均年龄为205.2±0.9 Ma，代表了沉积物的最大沉积年龄。这两个种群的潜在来源是在不列颠哥伦比亚省中部的Quesnel地体中发现的，这意味着该地体在晚三叠世与原生的北美边缘非常接近。这一点得到了地球化学和构造证据的支持。奎斯奈尔地体在晚三叠世接近今天的纬度，这一暗示与基于古地磁学和古生物学证据的旧的古纬度估计相矛盾。从最年轻的锆石群体中获得的年龄为205.2±0.9 Ma，也与最近公布的诺里安-Rhaetian边界年龄的估计一致。
New isotopic ages have been obtained from euhedral, first-cycle zircon grains recovered from Rhaetian strata preserved at the Black Bear Ridge section in northeastern British Columbia. Two statistically significant populations are present: an older population ca. 224 Ma, and a dominant younger population ca. 205 Ma. The younger population includes a group of grains with a weighted average 206 Pb/ 238 U age of 205.2 ± 0.9 Ma, which is interpreted to represent the maximum depositional age of the sediment. Potential sources for the two populations are found in the Quesnel terrane in central British Columbia, implying close proximity between this terrane and the autochthonous North American margin during the Late Triassic. This is supported by geochemical and structural evidence. The implication that the Quesnel terrane was close to its present-day latitude during the Late Triassic is in conflict with older estimates of paleolatitude based on paleomagnetic and paleontological evidence. The age of 205.2 ± 0.9 Ma obtained from the youngest population of zircons is also consistent with recently published estimates for the age of the Norian-Rhaetian boundary.