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Geochronology of calcite‐filled joints, southeast Canada: Insight into Late Cretaceous deformation of eastern North America
Terra Nova ( IF 2.4 ) Pub Date : 2020-05-30 , DOI: 10.1111/ter.12479
Jennifer Spalding 1 , David A. Schneider 1 , Julie Brown 2
Affiliation  

Resolving the timing of brittle tectonism is a challenge. We examined intra‐cratonic Middle Ordovician limestone bedrock that overlies Mesoproterozoic crystalline basement, which are both cut by ENE‐WSW trending fault zones that have historic M4‐5 earthquakes along their trace. Calcite‐filled mode I joints are ubiquitous within the strata, and are parallel to the modern stress field. Calcite δ18O and δ13C values are analogous to the bulk composition of Middle Ordovician limestones, and suggest vein formation from a source dominated by connate fluids of the host rock. U‐Pb geochronology of six calcite veins sealing ENE‐WSW oriented joints produced similar Cretaceous dates and were regressed together yielding a date of 96.8 ± 1.1 Ma (MSWD: 2.9). A Cenomanian age is consistent with the most recent reorientation of North America's compressive stress field, which is attributed to a change in spreading direction along the northern Mid‐Atlantic Ridge and is linked to a global plate reorganization event at ca. 105–100 Ma. These results suggest that the most recent redistribution of lateral stress was not a passive event, and generated brittle deformation and fluid flow at least 500 km inland of North America's Atlantic passive margin.

中文翻译:

加拿大东南方解石填充缝的年代学:对北美东部晚白垩世形变的认识

解决脆性构造的时机是一个挑战。我们研究了中元古生界晶体基底之上的克拉通中奥陶纪石灰岩基岩,两者均被沿其轨迹具有历史M4-5地震的ENE-WSW趋势断裂带切割。方解石填充的I型接头在地层中无处不在,并且与现代应力场平行。方解石δ 18 O和δ 13C值类似于中奥陶纪石灰岩的整体组成,并暗示了由源岩原生流体主导的矿脉形成。密封ENE-WSW定向节理的6个方解石脉的U-Pb地质年代学产生了相似的白垩纪日期,并一起回归,产生了96.8±1.1 Ma的日期(MSWD:2.9)。新生代年龄与北美压应力场的最新方向一致,这归因于沿中大西洋中北部北部扩展方向的变化,并与全球一次板块重组事件有关。105-100马。这些结果表明,横向应力的最新分布不是被动事件,而是在北美大西洋被动边缘内陆至少500 km处产生脆性变形和流体流动。
更新日期:2020-05-30
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