Crust-formaticn processes in the Kontum Massif, Vietnam

位于越南中部的Kontum Bagraf由低级片岩和角闪岩-麻粒岩相变质岩组成，这些岩石曾被S型和I型花岗岩侵入。该岩群以前被认为主要由太古代麻粒岩（Kannak杂岩）、元古代角闪岩相变质岩（Ngoc Linh杂岩）和低级片岩（Kham Duc杂岩）组成。它们被认为是东南亚的印度支那盆地的基底。Kannak杂岩主要由在高温至超高温（UHT）条件下变质成麻粒岩相的泥质-半泥质片麻岩组成。少量的镁铁质和钙硅酸盐岩石也夹在片麻岩中。最高级变质条件由石榴子石-斜方辉石-硅线石-堇青石片麻岩确定，表明退变质阶段多期合晶岩的形成是从超高温（1000 ℃以下）等温减压开始的。另一方面，在一项研究中， 关于我们 新发现的榴辉岩-单斜辉石-斜方辉石麻粒岩（榴辉岩超高温镁铁质麻粒岩）显示出从石榴石-单斜辉石-石英到角闪石-石英的一系列变化。研究表明，这些岩石是等温减压-近等压冷却变质演化的结果。1.2 GPa和CA。1050 ℃（M1变质）。高压M0变质作用（约1.7 GPa<，ca. 1000 ℃），属于超高压变质作用的一部分; M2低压（但仍为超高温）变质作用（0.9-1.0 GPa，约1000 ℃）。1000 ℃）是顺时针压力-温度演化过程中退变质作用的一部分。广泛报道的二叠纪-三叠纪变质事件（约。240-260 Ma），表明东亚大陆碰撞过程中经历了从M0阶段到低压低温退变质阶段（M2晚期）的快速变质演化。Kannak和Ngoc Linh杂岩的Sm-Nd等时线和SHRIMP年龄也表明Kontum Bagraf也经历了泛非变质事件（约1000年）。2.5、1.0和0.5Ga）。目前已发表的41篇关于Kontum Bronzf变质作用演化的研究成果，对研究东亚大陆演化过程具有很强的制约作用。少

The Kontum massif in central Vietnam consists of low-grade schists and amphibolite- to granulite-facies metamorphic rocks, that have been intruded by S-type and I-type granites. This terrane was formerly considered to be composed mainly of Archean granulites (the Kannak Complex), Proterozoic amphibolite-facies metamorphic rocks (the Ngoc Linh Complex) and low-grade schists (the Kham Duc Complex). They were thought to be the basement of the Indochina Craton in south-east Asia. The Kannak Complex is dominated by pelitic-semipelitic gneisses metamorphosed under high- to ultrahigh-temperature (UHT) conditions into granulite-facies. A minor amount of mafic and calcsilicate rocks are also intercalated within the gneisses. The highest-grade metamorphic condition is determined from garnet-orthopyroxene-sillimanite-cordierite gneiss, which indicates that multi-stage symplectite formation during retrograde stage started from isothermal decompression in UHT condition (1000 ℃<). On the other hand, … More the newly found garnet-clinopyroxene-orthopyroxene granulites (eclogitic ultrahigh-temperature mafic granulite) from the Ngoc Linh Complex shows a series of changes in divariant assemblages from garnet-clinopyroxene-quartz to hornblende-quartz through clinopyroxene-orthopyroxene- plagioclase-(garnet). It was identified that these rocks were formed as a result of their metamorphic evolution of isothermal decompression followed by nearly isobaric cooling.The ultrahigh-temperature metamorphic rocks in the Kontum massif, which are exposed along the Dac To Kan shear zone, show a clockwise pressure-temperature path with the peak metamorphic condition of ca. 1.2 GPa and ca. 1050 ℃ (M1 metamorphism). High-pressure M0 metamorphism (ca. 1.7 GPa<, ca. 1000 ℃) as part of the prograde metamorphism and low-pressure (but still ultrahigh-temperature) M2 metamorphism (0.9-1.0 GPa,ca. 1000 ℃) as part of the retrograde metamorphism during the clockwise pressure-temperature evolution are also recognized. The widely reported Permo-Triassic metamorphic event (ca. 240-260 Ma) from the ultrahigh-temperature metamorphic rocks would indicate a rapid metamorphic evolution from M0 stage to low-pressure and low-temperature retrograde stage (later M2 stage) during the continents collision in eastern Asia. The newly determined Sm-Nd internal isochron and SHRIMP ages from the Kannak and Ngoc Linh Complexes would also indicate that the Kontum massif had also undergone the Pan African metamorphic event (ca. 2.5,1.0 and 0.5 Ga). The present results of the metamorphic evolution of the Kontum massif including 41 journal papers indicate a strong constraint to consider the coninental evolution process in Eastern Asia. Less