Mullite-corundum-spinel-cordierite-plagioclase xenoliths in the Skaergaard Marginal Border Group: multi-stage interaction between metasediments and basaltic magma
Mullite-corundum-spinel-cordierite-plagioclase xenoliths in the Skaergaard Marginal Border Group: multi-stage interaction between metasediments and basaltic magma
复制标题
斯卡尔加德边缘群中的莫来石-刚玉-尖晶石-堇青石-斜长石捕虏体：变质沉积物与玄武质岩浆之间的多阶段相互作用
DOI：
10.1007/s00410-004-0644-5
复制
发表时间：
2005
影响因子：
3.5
通讯作者：
G. Markl
中科院分区：
文献类型：
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作者：
G. Markl
变质围岩的接触和热变质的第三Skaergaard侵入，东格陵兰。在加热的初始阶段，虽然它们可能仍然在主岩接触晕内，但它们超越了平衡和不平衡熔融反应的范围，产生了花岗岩熔体和非常耐火的尖晶石+堇青石+斜长石±尖晶石残留物。这些耐火岩石的一部分在作为捕虏体被夹带到Skaergaard Marginal Border Group中后，经历了另一次熔融事件，在那里它们经历了约1，000 °C的温度，约650巴的压力和低于FMQ缓冲区约0.2-0.5 log单位的氧逸度。在这里，它们经历了大量熔融，但没有与Skaergaard岩浆混合，可能是因为高粘度对比。富铝熔体结晶为富铝+莫来石+硅线石+斜长石+尖晶石+金红石±鳞石英±堇青石的组合，它们与周围的玄武岩反应，产生强烈的斜长石（靠近玄武岩的An 55到靠近富铝熔体的An 90）的隐带边缘。在捕虏体的内部部分的组合提供了纹理的证据，由于在高粘度，可能是无水富铝熔体中的缓慢扩散的不平衡增长。较低温度的铁玄武质-花岗斑岩熔体与捕虏体沿着边缘和沿着裂隙的相互作用导致尖晶石和莫来石的消耗，并在800°C左右形成稳定的尖晶石+堇青石+斜长石+石英+钾长石+磁铁矿+钛铁矿组合。
Metapelitic country rocks were contact- and pyro-metamorphosed by the Tertiary Skaergaard Intrusion, East Greenland. In an initial stage of heating, while they were probably still in place within the host rock contact aureole, they overstepped a range of equilibrium and disequilibrium melting reactions and produced both a granitic melt and very refractory spinel+cordierite+plagioclase±corundum residuals. Parts of these refractory rocks were then subjected to another melting event after being entrained as xenoliths into the Skaergaard Marginal Border Group, where they experienced a temperature of about 1,000°C at a pressure of about 650 bars and at an oxygen fugacity about 0.2–0.5 log units below the FMQ buffer. Here, they underwent bulk melting, but did not mix with the Skaergaard magma, presumably because of the high viscosity contrast. The Al-rich melts crystallized to an assemblage of corundum+mullite+sillimanite+ plagioclase+spinel+rutile±tridymite±cordierite and they reacted with the surrounding basalt producing a strongly cryptically zoned rim of plagioclase (An55 close to the basalt to An90 close to the Al-rich melt). The assemblage in the inner parts of the xenoliths provides textural evidence for disequilibrium growth due to slow diffusivities in the highly viscous, probably water-free Al-rich melt. Later interaction of lower temperature ferrobasaltic to granophyric melts with the xenoliths along their margins and along cracks led to consumption of corundum and mullite and to the stable assemblage of spinel+cordierite+plagioclase+quartz+K-feldspar +magnetite+ilmenite at about 800°C.