Laurentian provenance and an intracratonic tectonic setting for the Moine Supergroup, Scotland, constrained by detrital zircons from the Loch Eil and Glen Urquhart successions

Detrital zircons in psammite from the type section of the Loch Eil Group of the Moine Supergroup, NW Scotland, and from an
unnamed quartzose psammite, interstratified with marble, at Glen Urquhart yield similar U–Pb detrital zircon ages ranging
from c. 2300 to 900 Ma. Both samples show age peaks at c. 1680–1630 Ma, 1510–1490 Ma, 1430–1330 Ma and 1110–1040 Ma. Archaean age grains are absent and Palaeoproterozoic grains older
than 1800 Ma are rare. Sediment accumulation occurred in the early Neoproterozoic post c. 900 Ma but prior to emplacement of the 870 Ma West Highland granite gneiss. The Glen Urquhart sample has previously been
considered to form part of the Albynian sequence lying between the Moine and Dalradian supergroups. The similar detrital zircon
age signature of the two samples is consistent with the Glen Urquhart material representing part of the upper Moine succession.
In both samples, detrital age peaks at around 1650 Ma and 1500 Ma correspond closely to the Labradorian and Pinware magmatic
events in NE Laurentia and Baltica whereas the younger age peaks at c. 1400 and 1100 Ma correspond to phases of the Grenville orogen in Laurentia. The presence of detritus at c. 1650 Ma argues against input from Amazonia, which lacks any recorded magmatic activity in the range 1700–1600 Ma. The absence
of Archaean and late Palaeoproterozoic detritus, which is present in Laurentia-derived units younger than the Moine, such
as the Dalradian and Western Newfoundland strata, suggests that the Labradorian and Pinware magmatic arcs retained sufficient
topographic relief to mask and block any input of older detritus into the Neoproterozoic Moine basin. The Laurentian provenance
of the zircons argues against an exotic origin for the Moine Supergroup. Palaeogeographical reconstructions suggest that the
Moine succession accumulated in an intracratonic setting within Rodinia near the nexus of Laurentia, Baltica and Amazonia.
Closure during the mid-Neoproterozoic of this site of lithospheric extension along with its record of Knoydartian deformation
and metamorphism may be analogous to the intracratonic tectonic history of central Australia during the Neoproterozoic and
Palaeozoic that developed in response to far-field effects on the active Gondwana margin.

洛伊尔群莫伊恩超群类型剖面及格伦乌尔夸特地区未命名石英砂岩中的碎屑锆石，与大理岩互层，其U-Pb碎屑锆石年龄范围约为23亿至9亿年。两个样本均显示出约16.8亿至16.3亿年、15.1亿至14.9亿年、14.3亿至13.3亿年和11.1亿至10.4亿年的年龄峰值。古老时代和早元古代大于18亿年的碎屑锆石极为罕见。沉积物的堆积发生在约9亿年后、8.7亿年西高地花岗岩片麻岩侵入之前的新元古代早期。格伦乌尔夸特样本先前被认为构成介于莫伊恩和达尔里安超群之间的阿尔比恩序列的一部分。两个样本中相似的碎屑锆石年龄特征表明，格伦乌尔夸特材料可能是上莫伊恩层序的一部分。在两个样本中，约16.5亿年和15亿年的碎屑年龄峰值与东北劳伦西亚和巴尔提克的拉布拉多和皮纳韦熔岩事件密切相关，而约14亿年和11亿年的较年轻年龄峰值则对应于劳伦西亚的格林维尔造山运动阶段。约1650年的碎屑存在排除了来自亚马逊地区的输入，因为该地区在17亿至16亿年范围内没有记录到的熔岩活动。古老时代和晚元古代的碎屑缺失，这表明拉布拉多和皮纳韦熔岩弧保持了足够的地形高差，以掩盖和阻止更古老碎屑输入到新元古代莫伊恩盆地。锆石的劳伦西亚来源排除了莫伊恩超群的异源起源。古地理重建表明，莫伊恩层序在罗迪尼亚内部的克拉通环境中积累，位于劳伦西亚、巴尔提克和亚马逊地区的交汇处。中元古代中期该地区岩石圈伸展的闭合，以及其记录的诺伊亚特变形和变质作用，可能与新元古代和古生代的澳大利亚中部克拉通内构造历史相似，这是对活跃冈瓦纳边缘远场效应的响应。