Abstract Garnet is common in metamorphic rocks and can be used to efficiently constrain pressure–temperature conditions experienced during orogenesis; however, it may also crystallize as a primary phase in many types of magma, which can complicate deciphering the petrogenesis of meta-igneous rocks. In this study, geochronological and geochemical analyses of garnet and zircon were integrated to constrain garnet genesis in plagioclase-absent mafic granulite from the Jiao-Liao-Ji Belt, North China Craton. The rare earth element patterns show an equilibrium relationship between garnet and metamorphic zircon, indicating that garnet has a metamorphic origin. U–Pb dating shows that garnet has a whole-grain age of c. 1.83 Ga, with no difference between core and rim domains, which is slightly younger than metamorphic ages recorded by zircon (c. 1.87 Ga). The age difference between garnet and zircon is likely a result of differences in their closure temperature for the U–Pb isotope system. The mineral assemblage garnet + clinopyroxene + K-feldspar + titanite shows textural equilibration and was used to determine peak pressure–temperature conditions of 0.8–1.2 GPa at 830–880 °C. Given the age of high-pressure metamorphism (c. 1.87 Ga) calculated here being younger than c. 1.95–1.90 Ga proposed by previous studies for the west Liaodong peninsula, we suggest that c. 1.95–1.87 Ga represents the timing of progressive collision between the Longgang Block and the Nangrim Block, with the western part having collided slightly earlier than the eastern part.

中文翻译：

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解读变质火成岩中石榴石的成因——以华北克拉通胶辽冀带为例

摘要 石榴石在变质岩中很常见，可用于有效约束造山过程中的压力-温度条件；然而，它也可能在许多类型的岩浆中结晶为主要相，这会使破译变质火成岩的岩石成因变得复杂。在这项研究中，结合石榴石和锆石的年代学和地球化学分析，限制了华北克拉通胶辽冀带无斜长石基性麻粒岩中石榴石的成因。稀土元素图案显示石榴石与变质锆石之间的平衡关系，表明石榴石具有变质成因。U-Pb 测年显示石榴石的全麦年龄为 c。1.83 Ga，核域和边缘域之间没有差异，比锆石记录的变质年龄略年轻（约 1.87 Ga）。石榴石和锆石之间的年龄差异可能是由于 U-Pb 同位素系统的闭合温度不同造成的。矿物组合石榴石 + 单斜辉石 + 钾长石 + 钛石显示出结构平衡，并用于确定 830-880 °C 下 0.8-1.2 GPa 的峰值压力 - 温度条件。鉴于这里计算出的高压变质作用年龄（约 1.87 Ga）小于 c。1.95-1.90 Ga 以前的研究为辽东半岛西部提出，我们建议 c. 1.95～1.87 Ga代表龙岗块体与南格里姆块体渐进碰撞时间，西部碰撞时间略早于东部。矿物组合石榴石 + 单斜辉石 + 钾长石 + 钛石显示出结构平衡，并用于确定 830-880 °C 下 0.8-1.2 GPa 的峰值压力 - 温度条件。鉴于这里计算出的高压变质作用年龄（约 1.87 Ga）小于 c。1.95-1.90 Ga 以前的研究为辽东半岛西部提出，我们建议 c. 1.95～1.87 Ga代表龙岗块体与南格里姆块体渐进碰撞时间，西部碰撞时间略早于东部。矿物组合石榴石 + 单斜辉石 + 钾长石 + 钛石显示出结构平衡，并用于确定 830-880 °C 下 0.8-1.2 GPa 的峰值压力 - 温度条件。鉴于这里计算出的高压变质作用年龄（约 1.87 Ga）小于 c。1.95-1.90 Ga 以前的研究为辽东半岛西部提出，我们建议 c. 1.95～1.87 Ga代表龙岗块体与南格里姆块体渐进碰撞时间，西部碰撞时间略早于东部。前人对辽东半岛西部的研究提出的 90 Ga，我们建议 c．1.95～1.87 Ga代表龙岗块体与南格里姆块体渐进碰撞时间，西部碰撞时间略早于东部。前人对辽东半岛西部的研究提出的 90 Ga，我们建议 c．1.95～1.87 Ga代表龙岗块体与南格里姆块体渐进碰撞时间，西部碰撞时间略早于东部。