Continental growth and reworking on the edge of the Columbia and Rodinia supercontinents; 1.86–0.9 Ga accretionary orogeny in southwest Fennoscandia

Geological history from the late Palaeoproterozoic to early Neoproterozoic is dominated by the formation of the supercontinent Columbia, and its break-up and re-amalgamation into the next supercontinent, Rodinia. On a global scale, major orogenic events have been tied to the formation of either of these supercontinents, and records of extension are commonly linked to break-up events. Presented here is a synopsis of the geological evolution of southwest Fennoscandia during the ca. 1.9–0.9 Ga period. This region records a protracted history of continental growth and reworking in a long-lived accretionary orogen. Three major periods of continental growth are defined by the Transscandinavian Igneous Belt (1.86–1.66 Ga), Gothian (1.66–1.52 Ga), and Telemarkian (1.52–1.48 Ga) domains. The 1.47–1.38 Ga Hallandian–Danopolonian period featured reorganization of the subduction zone and over-riding plates, with limited evidence for continental collision. During the subsequent 1.38–1.15 Ga interval, the region is interpreted as being located inboard of a convergent margin that is not preserved today and hosted magmatism and sedimentation related to inboard extensional events. The 1.15–0.9 Ga period is host to Sveconorwegian orogenesis that marks the end of this long-lived accretionary orogen and features significant crustal deformation, metamorphism, and magmatism. Collision of an indenter, typically Amazonia, is commonly inferred for the cause of widespread Sveconorwegian orogenesis, but this remains inconclusive. An alternative is that orogenesis merely represents subduction, terrane accretion, crustal thickening, and burial and exhumation of continental crust, along an accretionary margin. During the Mesoproterozoic, southwest Fennoscandia was part of a much larger accretionary orogen that grew on the edge of the Columbia supercontinent and included Laurentia and Amazonia amongst other cratons. The chain of convergent margins along the western Pacific is the best analogue for this setting of Proterozoic crustal growth and tectonism.

古元古代晚期至新元古代早期的地质历史，以超大陆哥伦比亚（Columbia）的形成、裂解并重新拼合为后续超大陆罗迪尼亚（Rodinia）为主线。全球尺度下，主要造山事件均与这两个超大陆之一的形成相关，而伸展作用的记录通常与超大陆裂解事件存在关联。本文呈现的是芬诺斯坎迪亚（Fennoscandia）西南部在约1.9–0.9 Ga时期的地质演化概览。该区域记录了长期增生造山带中大陆生长与地壳再造的漫长演化历史。三个主要的大陆生长阶段分别对应跨斯堪的纳维亚火成岩带（Transscandinavian Igneous Belt，1.86–1.66 Ga）、哥特期（Gothian，1.66–1.52 Ga）以及泰勒马克期（Telemarkian，1.52–1.48 Ga）地质域。1.47–1.38 Ga的哈兰-达诺波洛尼期（Hallandian–Danopolonian）以俯冲带与上覆板块的重组为特征，仅存在有限的大陆碰撞证据。在随后的1.38–1.15 Ga时段，该区域被认为位于现今未被保存下来的汇聚陆缘内侧，发育了与内侧伸展事件相关的岩浆作用与沉积作用。1.15–0.9 Ga时期则发生了斯维科诺尔韦造山作用（Sveconorwegian orogenesis），标志着这个长期演化的增生造山带的终结，其特征包括显著的地壳变形、变质作用与岩浆活动。通常认为广泛发育的斯维科诺尔韦造山作用是由一个楔入体（一般为亚马孙克拉通（Amazonia））的碰撞所引发，但这一推论仍未定论。另一种假说则提出，该造山作用仅代表沿增生陆缘发生的俯冲、地体增生、地壳增厚以及大陆地壳的埋藏与折返过程。中元古代时期，芬诺斯坎迪亚西南部隶属于规模更为庞大的增生造山带，该造山带发育于哥伦比亚超大陆的边缘，同时包含劳伦大陆（Laurentia）与亚马孙克拉通等其他克拉通。现今西太平洋的汇聚陆缘链，是元古代地壳生长与构造活动这一构造背景的最佳类比实例。