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Tectonothermal evolution of a collisional orogen in the Khammam region, southeastern India: insights from structures, phase equilibria modeling and U–Th–(total) Pb monazite geochronology
Contributions to Mineralogy and Petrology ( IF 3.5 ) Pub Date : 2020-11-11 , DOI: 10.1007/s00410-020-01744-7
H. Hrushikesh , Praveen C. Singh , N. Prabhakar , Sachin K. Thakur , Bidisha Dey

The Khammam Schist Belt (KSB), southeastern India, represents a part of the collision zone that is sandwiched between the Eastern Dharwar Craton to the west and the Eastern Ghats Mobile Belt (EGMB) to the east. Quartzofeldspathic gneisses of the EGMB and garnet–kyanite metapelites of the KSB have been investigated to characterize P–T–t evolution of the Khammam region. Pseudosection modeling reveals that the melt-bearing quartzofeldspathic gneiss experienced peak and post-peak metamorphism at P–T conditions of 7.9–8.1 kbar/790–810 °C and ~ 7.0 kbar/740–750 °C, respectively. In contrast, metapelite witnessed peak metamorphism at 7.4–7.8 kbar/600–640 °C, followed by post-peak retrogression at 6.1–6.6 kbar/590–625 °C. U–Th–(total) Pb monazite ages from the gneiss constrain the peak and retrograde metamorphic episodes at 1.63–1.53 Ga and 1.48–1.38 Ga, while those in the metapelites were determined at 1.25–1.20 Ga and 1.18–1.10 Ga, respectively. These P–T–t estimates indicate that the KSB, Vinjamuru, and Ongole domains evolved distinctly during Late Paleoproterozoic–Late Mesoproterozoic. The younger ages (0.90–0.81 Ga) were ascribed to the formation of the Eastern Indian Tectonic Zone, implying its extension beyond the western margin of the EGMB. Besides, the distinct Neoarchean ages (2.79–2.45 Ga) are related to the Archean protolith of the quartzofeldspathic gneisses, which were likely derived from the Archean crust of the Napier–Rayner Complex. This tectonothermal restoration is new and characterizes the Khammam region as the hot and composite collision zone with protracted geological history. (250 words)

中文翻译:

印度东南部 Khammam 地区碰撞造山带的构造热演化:来自结构的见解、相平衡模型和 U-Th-(总)Pb 独居石年代学

印度东南部的哈曼片岩带 (KSB) 代表了夹在西部的东达尔瓦尔克拉通和东部的东高止山脉移动带 (EGMB) 之间的碰撞带的一部分。已经研究了 EGMB 的石英长石片麻岩和 KSB 的石榴石-蓝晶石变泥质岩,以表征 Khammam 地区的 P-T-t 演化。伪剖面模型显示,含熔体的石英长石片麻岩分别在 7.9–8.1 kbar/790–810 °C 和 ~ 7.0 kbar/740–750 °C 的 P-T 条件下经历了峰值和峰值后变质作用。相比之下,变泥质岩在 7.4-7.8 kbar/600-640 °C 处见证了峰值变质作用,随后在 6.1-6.6 kbar/590-625 °C 处出现峰值后退变。片麻岩中的 U–Th–(总)Pb 独居石年龄将峰值和逆行变质事件限制在 1.63–1.53 Ga 和 1.48–1.38 Ga,而那些在超泥质岩中的含量分别测定为 1.25-1.20 Ga 和 1.18-1.10 Ga。这些 P-T-t 估计表明 KSB、Vinjamuru 和 Ongole 域在晚古元古代 - 晚中元古代期间进化明显。较年轻的年龄(0.90-0.81 Ga)归因于东印度构造带的形成,这意味着其延伸到 EGMB 的西缘之外。此外,明显的新太古代时代(2.79-2.45 Ga)与石英长石片麻岩的太古代原岩有关,这很可能来自纳皮尔-雷纳复合体的太古代地壳。这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 分别。这些 P-T-t 估计表明 KSB、Vinjamuru 和 Ongole 域在晚古元古代 - 晚中元古代期间进化明显。较年轻的年龄(0.90-0.81 Ga)归因于东印度构造带的形成,这意味着其延伸到 EGMB 的西缘之外。此外,明显的新太古代时代(2.79-2.45 Ga)与石英长石片麻岩的太古代原岩有关,这些原岩很可能来自纳皮尔-雷纳杂岩体的太古代地壳。这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 分别。这些 P-T-t 估计表明 KSB、Vinjamuru 和 Ongole 域在晚古元古代 - 晚中元古代期间进化明显。较年轻的年龄(0.90-0.81 Ga)归因于东印度构造带的形成,这意味着其延伸到 EGMB 的西缘之外。此外,明显的新太古代时代(2.79-2.45 Ga)与石英长石片麻岩的太古代原岩有关,这些原岩很可能来自纳皮尔-雷纳杂岩体的太古代地壳。这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 90-0.81 Ga)归因于东印度构造带的形成,这意味着其延伸超出了 EGMB 的西缘。此外,明显的新太古代时代(2.79-2.45 Ga)与石英长石片麻岩的太古代原岩有关,这些原岩很可能来自纳皮尔-雷纳杂岩体的太古代地壳。这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 90-0.81 Ga)归因于东印度构造带的形成,这意味着其延伸超出了 EGMB 的西缘。此外,明显的新太古代时代(2.79-2.45 Ga)与石英长石片麻岩的太古代原岩有关,这些原岩很可能来自纳皮尔-雷纳杂岩体的太古代地壳。这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字) 这种构造热修复是新的,它将 Khammam 地区描述为具有长期地质历史的热复合碰撞带。(250 字)
更新日期:2020-11-11
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