The Nautanen deformation zone in the Gällivare area of northern Sweden is a highly Cu-mineralized, magnetite-rich, large-scale shear zone with a long-lived (~100 m.y.) deformation, hydrothermal alteration, and mineralization history. This composite structure hosts the Aitik porphyry Cu-Au-Ag ± Mo deposit and several Cu-Au ± Fe ± Ag ± Mo occurrences assigned to the iron oxide copper-gold (IOCG) deposit class. The Nautanen deformation zone was a locus for polyphase deformation and intermittent metasomatic-hydrothermal activity that overprinted middle Orosirian (ca. 1.90–1.88 Ga) continental arc-related volcanic-plutonic rocks. The deformation zone is characterized by intense shearing fabrics that form a series of subvertical to moderately W-dipping, NNW-SSE–trending, first-order shear zones with oblique reverse kinematics and related NNE-SSW–oriented second-order shear zones that control hydrothermal alteration patterns and Cu-Au mineralization.Hydrothermal alteration in the study area formed during several phases. Volcanic-volcaniclastic rocks to the east and west of the Nautanen deformation zone display low to moderately intense, pervasive to selectively pervasive (i.e., patchy zones or bands, disseminations) sericite ± feldspar, amphibole + biotite + magnetite ± tourmaline, and K-feldspar + hematite alteration. Both the amphibole + biotite and K-feldspar + hematite associations occur adjacent to NNW- and NE-oriented deformation zones and are locally associated with minor sulfide. Within the deformation zone, a moderate to intense biotite + amphibole + garnet + magnetite + tourmaline + sericite alteration assemblage is typically associated with chalcopyrite + pyrrhotite + pyrite and forms linear and subparallel, mainly NNW-oriented seams, bands, and zones that locally appear to overprint possibly earlier scapolite + sericite ± feldspar alteration. Late-stage epidote ± quartz ± feldspar alteration (retrograde saussuritization) forms selectively pervasive zones and epidote veinlets across the area and is partly related to brittle faulting.A magnetite-amphibole-biotite–rich, penetrative S₁ foliation records shortening during early Svecokarelian-related deformation (D₁) and can be related to ca. 1.88 to 1.87 Ga arc accretion processes and basin inversion that overlaps with regional peak metamorphism to near mid-amphibolite facies conditions and a potential initial Cu mineralization event. Folding and repeated shearing along the Nautanen deformation zone can be assigned to a second, late-Svecokarelian deformation event (D₂ stage, ca. 1.82–1.79 Ga) taking place at a higher crustal level. This D₂ deformation phase is related to late-stage accretionary processes active during a transition to a stage of postorogenic collapse, and it was accompanied by abundant, syntectonic intrusions. D₂-related magmatism produced high-temperature and low-pressure conditions and represents a regional magmatic-hydrothermal event that controlled the recrystallization/remobilization of magnetite, biotite, and amphibole. Associated shear zone reactivation during D₂ favors the utilization of the Nautanen deformation zone as a fluid conduit, which preferentially controlled the siting and formation of epigenetic Cu-Au mineralization with distinctive IOCG characteristics within second-order shear zones.

中文翻译：

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古元古代上地壳带氧化铁铜金矿化及相关蚀变的结构控制：来自瑞典北部瑙塔宁变形带及周边地区的见解

瑞典北部 Gällivare 地区的 Nautanen 变形带是一个高度铜矿化、富含磁铁矿的大型剪切带，具有长寿命（~100 米）变形、热液蚀变和矿化历史。这种复合结构承载了 Aitik 斑岩 Cu-Au-Ag ± Mo 矿床和几个属于氧化铁铜-金 (IOCG) 矿床类别的 Cu-Au ± Fe ± Ag ± Mo 矿床。Nautanen 变形带是多相变形和间歇性交代-热液活动的所在地，覆盖了中奥罗斯纪（约 1.90-1.88 Ga）与大陆弧相关的火山深成岩。变形区的特征是强烈的剪切织物，形成一系列垂直到适度的 W 倾角，NNW-SSE 趋势，具有倾斜反向运动学的一级剪切带和相关的 NNE-SSW 定向二级剪切带，控制着热液蚀变模式和 Cu-Au 矿化。研究区的热液蚀变形成于几个阶段。Nautanen 变形带东部和西部的火山-火山碎屑岩显示出低到中等强度，普遍到选择性普遍（即斑块状带或带，散布）绢云母±长石，闪石+黑云母+磁铁矿±电气石和钾长石+ 赤铁矿蚀变。闪石 + 黑云母和钾长石 + 赤铁矿组合都出现在 NNW 和 NE 取向的变形带附近，并且局部与少量硫化物相关。在变形区内，中等到强度的黑云母 + 闪石 + 石榴石 + 磁铁矿 + 电气石 + 绢云母蚀变组合通常与黄铜矿 + 磁黄铁矿 + 黄铁矿相关，并形成线性和亚平行的，主要是 NNW 方向的接缝、带和区域，局部似乎叠印了可能早期的方柱石+ 绢云母 ± 长石蚀变。后期绿帘带 ± 石英 ± 长石蚀变（逆行索氏化）在该地区形成选择性普遍带和绿帘带细脉，部分与脆性断层有关。富含磁铁矿-闪石-黑云母的渗透性 S₁叶理在早期 Svecokarelian 相关变形 (D ₁ )期间记录缩短，并且可能与 ca。1.88 至 1.87 Ga 弧增生过程和盆地反转与区域峰值变质作用重叠至近中角闪岩相条件和潜在的初始铜矿化事件。沿着 Nautanen 变形带的褶皱和反复剪切可归因于在更高地壳水平上发生的第二个晚期 Svecokarelian 变形事件（D ₂阶段，约 1.82-1.79 Ga）。该D ₂变形阶段与后期增生过程有关，在向造山后塌陷阶段过渡期间活跃，并伴有丰富的同构造侵入体。d ₂相关的岩浆活动产生了高温和低压条件，代表了控制磁铁矿、黑云母和闪石的再结晶/再活动的区域性岩浆-热液事件。D ₂期间相关的剪切带重新激活有利于将 Nautanen 变形带用作流体管道，从而优先控制二阶剪切带内具有独特 IOCG 特征的表观成因 Cu-Au 矿化的选址和形成。