Tectonometamorphic evolution along the Iapetus suture zone in Newfoundland: Evidence for polyphase Salinic, Acadian and Neoacadian very low- to medium-grade metamorphism and deformation
Tectonometamorphic evolution along the Iapetus suture zone in Newfoundland: Evidence for polyphase Salinic, Acadian and Neoacadian very low- to medium-grade metamorphism and deformation
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纽芬兰土卫八缝合带沿线的构造变质演化：多相盐化、阿卡迪亚和新阿卡迪亚极低至中级变质作用和变形的证据
DOI：
10.1016/j.tecto.2018.05.023
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发表时间：
2018
期刊：
影响因子：
2.9
通讯作者：
Glodny
中科院分区：
文献类型：
--
作者：
Willner;van Staal;Zagorevski;Glodny
纽芬兰中部的红印度线 (RIL) 是缝合处，土卫八洋的主要区域在近冈瓦南维多利亚弧与复合活动劳伦特边缘的吸积过程中于约 452 Ma 闭合。这种软碰撞的长期变形历史始于~471Ma，伴随着海洋地体向活跃复合劳伦斯边缘的增生。土卫八闭合后，在志留纪和泥盆纪（盐化、阿卡迪亚和新阿卡迪亚造山旋回）期间，两个碰撞的活动边缘逐渐变形和变质。在变质场梯度从 ~12°C/km 增加到随着时间的推移，约为 32°C/km。通过白云母 40Ar/39Ar 点年龄和平台年龄、涉及白云母的附加 Rb-Sr 矿物等时线和钛矿的一个 U/Pb 年龄来测定多个变质结晶阶段。所有由此得出的年龄都在土卫八关闭后的 439±4Ma 和 356±16Ma 之间。两个横断面的结果有所不同：沿着穿过 RIL 区域的北部横断面观察到最古老的年龄为 443-421Ma（盐化造山旋回），具有最小的较年轻的叠印。因此，在塔科尼-盐岩逆冲过程中实现的低温、中高压条件（4.0–7.0kbar，230–340°C）得到了很好的保存。在阿卡迪亚右旋压断期间，塔科尼-盐岩构造楔呈垂直倾斜。相比之下，沿RIL带南部横断面的岩石主要显示阿卡迪亚年龄为408-390Ma，局部保存了更古老的年龄。阿卡迪亚变形发生在低温/低压条件下（~250–450°C，2.5–4.6kbar）。志留纪陆地覆盖岩也在这些条件下被埋藏。阿卡迪亚-新阿卡迪亚变形（393-340Ma）向西北方向变得更年轻，并逐渐局限于横断层带。浅地壳层面的最终前陆变形在 RIL 偏西北的纽芬兰中部建立了阿卡迪亚/新阿卡迪亚造山锋。
The Red Indian Line (RIL) in central Newfoundland is the suture, where the main tract of the Iapetus Ocean was closed at ~452 Ma during accretion of the peri-Gondwanan Victoria arc with the composite active Laurentian margin. The protracted deformation history of this soft collision started at ~471 Ma with accretion of oceanic terranes to the active composite Laurentian margin. After Iapetus closure both colliding active margins were progressively deformed and metamorphosed during Silurian and Devonian (Salinic, Acadian and Neoacadian orogenic cycles).Peak conditions of the very low- to medium-grade, heterogeneously distributed metamorphism were determined by pseudosection techniques within the range of 2–7 kbar, 230–450 °C during increase of the metamorphic field gradient from ~12 °C/km to ~32 °C/km over time. Multiple metamorphic crystallisation stages were dated by white mica40Ar/39Ar spot and plateau ages, additional Rb-Sr mineral isochrons involving white mica and one U/Pb age of titanite. All resulting ages between 439 ± 4 Ma and 356 ± 16 Ma postdate the closure of Iapetus.Results differ along two transects: The oldest ages of 443–421 Ma (Salinic orogenic cycle) were observed along the northern transect through the RIL zone with minimal younger overprint. Hence low temperature, intermediate to high pressure conditions (4.0–7.0 kbar, 230–340 °C) achieved during Taconic-Salinic underthrusting are well preserved. During Acadian dextral transpression the Taconic-Salinic structural wedge was tilted subvertically.In contrast, rocks along the southern transect through the RIL zone mainly show Acadian ages of 408–390 Ma with local preservation of older ages. Acadian deformation occurred under low temperature/low pressure conditions (~250–450 °C, 2.5–4.6 kbar). Also Silurian terrestrial cover rocks were buried under these conditions. Acadian-Neoacadian deformation (393–340 Ma) becomes younger towards the northwest and progressively localized in transcurrent fault zones. This final foreland deformation at shallow crustal level established the Acadian/Neoacadian orogenic front in central Newfoundland slightly northwest of the RIL.
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影响因子：
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作者：
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DOI：
--
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期刊：
影响因子：
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