Oriented lamellar inclusions of pyroxene and rutile in mantle garnet often serve as evidence for majoritic and titaniferous precursor garnets, respectively. We investigated ten new such microstructure-bearing samples from six orogenic peridotite bodies in SW Norway, which originated in the E Greenland mantle lithosphere, petrologically and thermobarometrically. All pyroxenite (nine) and eclogite (one) samples have large (mainly porphyroclastic) garnet containing silicate and oxide inclusions with shape-preferred orientation relationship. These inclusions vary—dependent on their size—systematically in shape (acicular to subprismatic), width (∼50 μm to submicron size), spacing (several 100 to ∼10 μm) and phase (pyroxene to Ti-oxide ± pyroxene). Smaller inclusions can fill the space between larger inclusions, which support the idea of consecutive generations. The larger, early formed lamellae occur least frequent and are most poorly preserved. A younger generation of other inclusions decorates healed cracks cutting across cores but not rims of garnet. These inclusions comprise oxides, silicates, carbonates (aragonite, calcite, magnesite) and fluid components (N2, CO2, H2O). The older, homogeneously distributed inclusions comply texturally and stoichiometrically with an origin by exsolution from excess Si- and Ti-bearing garnet. Their microstructural systematic variation demonstrates a similar early evolution of pyroxenite and eclogite. The younger inclusions in planar structures are ascribed to a metasomatic environment that affected the subcratonic lithosphere. The microstructure-bearing garnets equilibrated at ∼3.7 GPa (840 °C) and ∼3.0 GPa (710 °C), at a cratonic geotherm related to 37–38 mW m−2 surface heat flow. Some associated porphyroclastic grains of Mg-rich pyroxene have exsolution lamellae of Ca-rich pyroxene and vice versa that indicate a preceding cooling event. Projected isobaric cooling paths intersect isopleths for excess Si in garnet at ∼1550 °C, if an internally consistent thermodynamic data set in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) is applied (or ∼1600 °C if using CMAS). This temperature may confine the crystallisation of the unexsolved garnets at 100–120 km depths of the E Greenland subcratonic lithosphere. Tectonism is indicated in coastal and hinterland samples by porphyroclastic orthopyroxene with Al2O3 concentrations showing W-shaped profiles. Cores of associated large (>200 μm) recrystallised grains have low Al2O3 contents (0.18–0.23 wt.%). Both characteristics typify relatively short intracrystalline Al diffusion lengths and a prograde metamorphism into the diamond stability field. We assign this event to subduction during the Scandian orogeny. Porphyroclastic orthopyroxene in other samples shows U-shaped Al2O3 concentration profiles paired with long Al diffusion lengths (several 100 μm) that exceed the radius of recrystallised grains. Their cores contain high Al2O3 contents (0.65–1.16 wt.%), consistent with a diffusional overprint that obliterated prograde and peak metamorphic records. Unlike Al2O3, the CaO content in porphyroclastic orthopyroxene cores is uniform suggesting that early exhumation was subparallel to Ca isopleths in pressure–temperature space. The depth of sample origin implies that rock bodies of Scandian ultra-high pressure metamorphism occur in nearly the entire area betweenNordfjord and Storfjord and from the coast towards ∼100 km in the hinterland, i.e. in a region much larger than anticipated from crustal eclogite.

中文翻译：

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挪威西部片麻岩地区辉石岩和榴辉岩片状包裹体的亚克拉通和构造演化

地幔柘榴石中辉石和金红石的取向层状包裹体通常分别作为主要石榴石和含钛前体石榴石的证据。我们从岩石学和热气压学上研究了来自挪威西南部六个造山带橄榄岩体的十个新的这种含微结构的样品，这些橄榄岩体起源于格陵兰东部地幔岩石圈。所有辉石岩（九）和榴辉岩（一）样品都有大的（主要是斑碎屑）石榴石，含有硅酸盐和氧化物包裹体，具有形状优先的取向关系。这些夹杂物在形状（针状到亚棱柱状）、宽度（~50 μm 到亚微米大小）、间距（几个 100 到~10 μm）和相（辉石到氧化钛 ± 辉石）方面系统地变化——取决于它们的尺寸——变化。较小的夹杂物可以填充较大夹杂物之间的空间，这支持连续几代人的想法。较大的、早期形成的薄片出现频率最低，保存最差。年轻一代的其他内含物装饰着穿过核心但不是石榴石边缘的愈合裂缝。这些夹杂物包括氧化物、硅酸盐、碳酸盐（文石、方解石、菱镁矿）和流体成分（N2、CO2、H2O）。较老的、均匀分布的夹杂物在结构和化学计量上符合从过量的含硅和钛石榴石中析出的来源。它们的微观结构系统变化表明辉石岩和榴辉岩的早期演化相似。平面结构中较年轻的包裹体归因于影响次克拉通岩石圈的交代环境。含微结构的石榴石在 ∼3.7 GPa (840 °C) 和 ∼3.0 GPa (710 °C) 下平衡，在与 37-38 mW m-2 表面热流相关的克拉通地热。一些相关的富镁辉石斑碎屑颗粒具有富钙辉石的外溶片层，反之亦然，这表明之前的冷却事件。如果在系统 Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) 中应用内部一致的热力学数据集（如果使用 CMAS，则为 ～1600 °C），投影的等压冷却路径与石榴石中过量 Si 的等值线相交，温度约为 1550 °C ）。这个温度可能会限制未溶解的石榴石在 E 格陵兰次克拉通岩石圈 100-120 公里深度的结晶。在沿海和腹地样品中，斑碎屑斜方辉石表明构造作用，Al2O3 浓度呈 W 形分布。相关的大 (>200 μm) 再结晶晶粒的核心具有低 Al2O3 含量 (0.18–0.23 wt.%)。这两个特征都代表了相对较短的晶内铝扩散长度和进入金刚石稳定性领域的推进变质作用。我们将此事件分配给斯堪地亚造山运动期间的俯冲。其他样品中的斑碎屑斜方辉石显示 U 形 Al2O3 浓度分布与超过再结晶晶粒半径的长 Al 扩散长度（几个 100 μm）配对。它们的岩心含有较高的 Al2O3 含量（0.65-1.16 wt.%），这与抹去顺行和峰值变质记录的扩散叠印相一致。与 Al2O3 不同，斑碎屑斜方辉石核中的 CaO 含量是均匀的，这表明早期折返与压力 - 温度空间中的 Ca 等值线亚平行。