The Hamadan high-grade metapelites in the northwestern part of the Sanandaj–Sirjan zone, Iran, show a polymetamorphic evolution with relics of a garnet-bearing metamorphic mineral assemblage (M1), a contact metamorphic overprint (M2) related to the emplacement of the Middle to Late Jurassic Alvand composite pluton and a Buchan-type regional metamorphic event (M3) marked by ⁴⁰Ar/³⁹Ar ages in the 80–70 Ma range that is associated with penetrative ductile deformation producing a foliation and a thermal overprint onto the M2 assemblages. The M1 event is exclusively preserved as small garnet grains and mineral inclusions contained therein, incorporated into M2-stage cordierite porphyroblasts. Distinct metamorphic zones are developed over a region of ~ 600 km², which are partly correlated with distance to the composite pluton: zones (1) cordierite + K-feldspar hornfels, and (2) andalusite ± cordierite hornfels that surround the Alvand composite pluton at a distance of up to 5 km. These two zones are clearly related to M2 metamorphism associated with pluton emplacement. Zones (3) staurolite schist, (4) andalusite schist, and (5) sillimanite schist are found outside of the contact aureole and are considered to be the result of regional M3 metamorphism in the eastern part distant to the Alvand composite pluton. Conventional thermobarometry shows that temperatures in the area vary between ~ 560 and 660 °C for zones 1 and 2 and ~ 490 and 690 °C for zones 3–5. Phase equilibria modelling in the MnNCKFMASHT system indicates two distinct isobaric prograde paths at low pressures, at ~ 2.7 kbar for zones 1 and 2 and slightly higher pressures of around 3.5–5.5 kbar for zones 3–5. U–Th–Pb monazite geochronology revealed overlapping ages of 168 ± 11 Ma and 149 ± 19 Ma in the hornfels (1 and 2) and schistose (3–5) zones, respectively. These ages are similar to the intrusion age of the Alvand composite pluton (153.3 ± 2.7 to 166.5 ± 1.8 Ma) and are interpreted to reflect heating due to the emplacement of the composite pluton (M2 contact metamorphic event). However, ⁴⁰Ar/³⁹Ar dating of white mica and amphibole yielded plateau ages ranging from 80 to 69 Ma over the entire transect. The formation of schistosity in zones 3–5 postdates the intrusion and is thus related to M3 metamorphism. The white mica fabric indicates formation of the foliation during M3 garnet growth, which is followed by local retrogression of garnet to chlorite during exhumation. Consequently, the ⁴⁰Ar/³⁹Ar white mica and amphibole ages likely indicate reheating during M3 to more than ca. 500 ± 25 °C (argon retention temperature in amphibole). These data establish the occurrence of a Cretaceous, Buchan-style regional metamorphic event that had not been firmly identified before. Subsequent Late Cretaceous exhumation of the Hamadan complex with its high-grade metapelites is due to extension along the Tafrijan–Mangavi–Kandelan fault, which represents a major ductile low-angle normal fault. Metamorphic temperatures coupled with mineral ages from this and published work suggest a fast stage of cooling with a rate of ~ 6 °C/Ma during exhumation after M3 metamorphism.

伊朗Sanandaj–Sirjan带西北部的Hamadan高品位变质岩表现出多变质演化，其带有石榴石变质矿物组合（M1），接触变质叠印（M2）的遗迹。中侏罗纪晚期Alvand复合岩体和Buchan型区域变质事件（M3），其特征是在80-70 Ma范围内具有⁴⁰ Ar / ³⁹ Ar年龄，这与渗透性延性变形产生叶面和M2上的热套印有关的集合。M1事件仅保留为小的石榴石颗粒和其中包含的矿物包裹体，并掺入M2期堇青石成卟啉细胞中。在约600 km ^2的区域上形成了明显的变质带。，这与到复合岩体的距离部分相关：（1）堇青石+钾长石角质岩，以及（2）围绕Alvand复合岩体的最远距离为5 km的红柱石±堇青石角岩。这两个区域显然与与质子位置有关的M2变质作用有关。区域（3）星形胶岩片岩，（4）红柱石片岩和（5）硅线石片岩均位于接触金针之外，并被认为是远离Alvand复合岩体的东部区域M3变质作用的结果。传统的热压法显示，区域1和2的区域温度在560至660°C之间变化，区域3-5的温度在490至690°C之间变化。MnNCKFMASHT系统中的相平衡模型表明，在〜2的低压下，有两个不同的等压推进路径。1区和2区的压力为7 kbar，3-5区的压力大约为3.5-5.5 kbar。U–Th–Pb独居石年代学揭示了角f（1和2）和片状（3–5）区域的重叠年龄分别为168±11 Ma和149±19 Ma。这些年龄类似于Alvand复合岩钉的侵入年龄（153.3±2.7至166.5±1.8 Ma），并被解释为反映由于复合岩钉的位置而引起的加热（M2接触变质事件）。然而，8 Ma）并解释为反映由于复合质子的位置而引起的加热（M2接触变质事件）。然而，8 Ma）并解释为反映由于复合质子的位置而引起的加热（M2接触变质事件）。然而，白云母和闪石的⁴⁰ Ar / ³⁹ Ar测年在整个样带上的高原年龄从80到69 Ma。在侵入区3-5中形成了片岩性，这是侵入的晚期，因此与M3变质有关。白色云母织物表明在M3石榴石生长过程中形成了叶状结构，随后在挖掘尸体期间石榴石局部退缩为亚氯酸盐。因此，⁴⁰ Ar / ³⁹白云母和闪石的年龄可能表明在M3期间再加热到超过约200℃。500±25°C（在闪石中保留氩气的温度）。这些数据确定了白垩纪的布坎式区域变质事件的发生，该事件以前没有被明确地确定。随后的哈马丹复合岩及其高级变质岩的晚白垩世掘出是由于沿塔弗里扬-曼加维-坎德兰断裂带的延伸，这代表了主要的韧性低角度正断层。M3变质后的掘尸过程中，变质温度与矿物年龄的关系以及已发表的研究成果表明，该阶段的冷却较快，冷却速度约为6°C / Ma。