The spinel and quartz associations in high grade xenoliths from Tallante (S.E. Spain) and their potential use in geothermometry and barometry
The spinel and quartz associations in high grade xenoliths from Tallante (S.E. Spain) and their potential use in geothermometry and barometry
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塔兰特（西班牙东南部）高品位捕虏体中的尖晶石和石英组合及其在地温测量和气压测量中的潜在用途
DOI：
10.1007/bf00399708
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发表时间：
1983
影响因子：
3.5
通讯作者：
D. Vielzeuf
中科院分区：
文献类型：
--
作者：
D. Vielzeuf
在塔兰特的玄武岩中发现的一些捕虏体中观察到明显的尖晶石+石英组合。主要副长石为：石英-斜长石-硅线石-尖晶石-石榴石-钛铁矿-石墨*石英-斜长石-石榴石-正辉石-尖晶石-钛铁矿。尖晶石与石英之间常发育一薄堇青石边缘，这是(1)2Sp+5Q→1cd反应的结果。在石榴石周围的玻璃包覆自面体尖晶石的存在可归因于石榴石±硅长石±斜长石熔融反应。这些铝质岩石被解释为与玄武质岩浆（≃1100°C）处于热平衡的捕虏体。根据现有的地球气压计，初生副长石在约7 kb时结晶。这些捕虏体可能代表岩浆室壁的碎片，岩浆室可能位于大约26公里的深度。根据这些数据和其他文献资料，表明(2)Fe尖晶石+Mg堇青石+Mg尖晶石+Fe堇青石的交换反应可以用于地热测量，并校准了Sp-Cd地温计：T°K= - 1,763/ln Kd+0.378。此外，尖晶石-石英-堇青石组合（反应(1)）是一个潜在的地球晴雨表：P=PFe-(RT ln (aFe CdCd/aFe SpSp 2/ΔVs), PFe=−8.4T°C+9,295；T°K=−1,763/ln Kd+0.378 andΔVs=1.075 cal/bar。结果表明，塔兰特次生堇青石的结晶压力约为4kb。提出了一种预测p - t图中不同场的几何关系及其随组成变化的演化的方法。将其应用于Al2O3-FeO-MgO和Al2O3-(FeO+MgO)体系中尖晶石、硅线石、正辉石、石榴石和堇青石（+过量石英）的相关系，并提出了高温下k2o贫sio2饱和偏长晶的模型。talante捕虏体被认为是下地壳的样品，受到一个重要的热异常的严重改造，这也是火山作用的原因。
Remarkable spinel+quartz associations are observed in some xenoliths found in the Basaltic rocks from Tallante. The main primary parageneses are:* quartz — plagioclase — sillimanite — spinel — garnet — ilmenite — graphite* quartz — plagioclase — garnet — orthopyroxene — spinel — ilmenite.A thin cordierite rim is often developed between spinel and quartz, and is the result of the reaction (1) 2Sp+5Q→1 Cd. The existence around garnet of glass enclosing euhedral spinels has been ascribed to a garnet±sillimanite±plagioclase melting reaction.These aluminous rocks are interpreted as xenoliths in thermal equilibrium with a basaltic magma (≃1,100° C). According to available geobarometers, the primary parageneses crystallized at about 7 kb. These xenoliths could represent fragments of the walls of a magma chamber which would have been located at a depth of about 26 km.From these data and others available in the literature, it is shown that the exchange reaction (2) Fe spinel+Mg cordierite⇌Mg spinel+Fe cordierite can be used for geothermometric purposes, and a Sp-Cd geothermometer is calibrated:T°K=−1,763/ln Kd+0.378. In addition, the association spinel — quartz — cordierite (reaction (1)) is a potential geobarometer:P=PFe-(RT ln (aFe CdCd/aFe SpSp 2/ΔVs) withPFe=−8.4T° C+9,295;T° K= −1,763/ln Kd+0.378 andΔVs=1.075 cal/bar. It indicates a pressure of about 4 kb for the crystallization of the secondary cordierite from Tallante.A method to predict the geometrical relationships of divariant fields inP-Tdiagrams and their evolution as a function of changes in composition is developed. It is applied to phase relationships between spinel, sillimanite, orthopyroxene, garnet and cordierite (+excess quartz) in the systems Al2O3-FeO-MgO and Al2O3-(FeO+MgO) and a model is proposed for K2O-depleted SiO2-saturated metapelites at high temperature.The Tallante xenoliths are considered to be samples of a lower crust seriously modified by an important thermal anomaly which is also responsible for the volcanism.