Metamorphic evolution of UHT calc-silicate rocks from Rundvågshetta, Lützow Holm Complex (LHC), East Antarctica
Metamorphic evolution of UHT calc-silicate rocks from Rundvågshetta, Lützow Holm Complex (LHC), East Antarctica
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发表时间：
2007
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通讯作者：
M. Satish-Kumar;Y. Motoyoshi;D. Dunkley
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作者：
M. Satish-Kumar;Y. Motoyoshi;D. Dunkley
东南极L-霍尔姆杂岩中辉石片麻岩中的钙硅质斑岩保存了超高温变质作用的岩石学特征和微构造特征，为区域变质演化提供了新的思路。观察到花岗岩-石榴石+方解石+单斜辉石+斜长石+钛铁矿+/硅灰石+/方解石+/石英组合的三个不同模式比例的矿物学带。辉长花岗岩与斜长岩共生，最低峰期变质温度约830oC。观察到了几代不同化学成分的石榴石日冕和分解反应，包括石榴石、单斜辉石和硅灰石。在CAFSV系统中建立的活动性校正的部分岩石格子有助于约束峰期和退变质过程中P-T-X-fO2的演化。然后将这些结果与钛铁矿SHRIMP年代学进行补充，以考虑该地区的折返历史。结合已有的P-T-t演化模型，建立了L-霍尔姆杂岩中Rundvógshetta麻粒岩的地球动力学演化模型。
Calc-silicate boudins within the pyroxene gneiss at Rundvågashetta, Lützow-Holm Complex, East Antarctica preserve petrologic signatures of ultra-high temperature metamorphism and microstructures that gave insights to the regional metamorphic evolution. Three mineralogical zones of varying modal proportion of an assemblage of grandite-garnet + scapolite + clinopyroxene + plagioclase + titanite +/wollastonite +/calcite +/quartz are observed. Meionitic scapolite coexists with anorthite suggesting a minimum peak metamorphic temperature of ~830oC. Several generations of chemically distinct garnet corona and breakdown reactions involving garnet, scapolite clinopyroxene and wollastonite are observed. Activity corrected partial petrogentic grids, constructed in the CAFSV system, helped in constraining the P-T-X-fO2 evolution during peak and retrograde metamorphism. These results were then supplemented with titanite SHRIMP geochronology to consider the exhumation history of the region. Taking into account of the existing models on P-T-t evolution, a geodynamic evolution of the Rundvågshetta granulites within the Lützow-Holm Complex was formulated.