Crust-formaticn processes in the Kontum Massif, Vietnam

越南中部孔腾地块由低品位片岩和角闪岩-麻粒岩相变质岩组成，受到S型花岗岩和I型花岗岩的侵位。该地体以前被认为主要由太古宙麻粒岩(坎纳克杂岩)、元古界角闪岩相变质岩(Ngoc Linh杂岩)和低品位片岩(Kham Duc杂岩)组成。它们被认为是东南亚印度支那克拉通的地下室。卡纳克杂岩以泥质-半泥质片麻岩为主，片麻岩在高温-超高温条件下变质为麻粒岩相。片麻岩中还夹有少量的镁铁质岩石和方解硅酸盐岩石。石榴石-斜方辉石-硅线石-堇青石片麻岩的最高变质条件表明，退变质阶段的多期正长石形成始于超高温条件下(1000℃&lt；)的等温减压。另一方面，…此外，在Ngoc Linh杂岩中新发现的石榴石-单斜辉石-斜方辉石麻粒岩(榴辉超高温镁铁质麻粒岩)显示了从石榴石-单斜辉石-石英到角闪石-石英通过单斜辉石-斜辉石-斜长石-(石榴石)的一系列不同组合的变化。昆腾地块中的超高温变质岩呈顺时针方向的压力-温度路径，峰期变质条件约为1.2℃和1050 Gpa(M1变质作用)。在顺时针压力-温度演化过程中，高压M0变质作用(约1.7 Gpa&lt；，约1000℃)和低压(但仍为超高温)M2变质作用(约0.9-1.0 Gpa，约1000℃)是逆行变质作用的一部分。超高温变质岩中广泛报道的二叠纪-三叠纪变质事件(约240-260 Ma)表明，东亚大陆碰撞过程中，变质作用从M0阶段快速演化到低压低温退变阶段(M2后期)。新测定的Kannak和Ngoc Linh杂岩的Sm-ND等时线和SHRIMP年龄也表明Kontom地块也经历了泛非变质事件(约2.5、1.0和0.5Ga)。目前对Kontom地块变质演化的研究结果(包括41篇期刊论文)表明，考虑东亚大陆的演化过程具有很强的约束性。较少

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