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首页> 外文期刊>Contributions to Mineralogy and Petrology >Crystal reaming during the assembly, maturation, and waning of an eleven-million-year crustal magma cycle: thermobarometry of the Aucanquilcha Volcanic Cluster
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Crystal reaming during the assembly, maturation, and waning of an eleven-million-year crustal magma cycle: thermobarometry of the Aucanquilcha Volcanic Cluster

机译：一千一百万年地壳岩浆周期的组装，成熟和减弱期间的晶体扩孔：奥坎基尔查火山群的热压法

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摘要

Phenocryst assemblages of lavas from the long-lived Aucanquilcha Volcanic Cluster (AVC) have been probed to assess pressure and temperature conditions of pre-eruptive arc magmas. Andesite to dacite lavas of the AVC erupted throughout an 11-million-year, arc magmatic cycle in the central Andes in northern Chile. Phases targeted for thermobarometry include amphibole, plagioclase, pyroxenes, and Fe–Ti oxides. Overall, crystallization is documented over 1–7.5 kbar (~25 km) of pressure and ~680–1,110 °C of temperature. Pressure estimates range from ~1 to 5 kbar for amphiboles and from ~3 to 7.5 kbar for pyroxenes. Pyroxene temperatures are tightly clustered from ~1,000–1,100 °C, Fe–Ti oxide temperatures range from ~750–1,000 °C, and amphibole temperatures range from ~780–1,050 °C. Although slightly higher, these temperatures correspond well with previously published zircon temperatures ranging from ~670–900 °C. Two different Fe–Ti oxide thermometers (Andersen and Lindsley 1985; Ghiorso and Evans 2008) are compared and agree well. We also compare amphibole and amphibole–plagioclase thermobarometers (Ridolfi et al. 2010; Holland and Blundy 1994; Anderson and Smith 1995), the solutions from which do not agree well. In samples where we employ multiple thermometers, pyroxene temperature estimates are always highest, zircon temperature estimates are lowest, and Fe–Ti oxide and amphibole temperature estimates fall in between. Maximum Fe–Ti oxide and zircon temperatures are observed during the middle stage of AVC activity (~5–3 Ma), a time associated with increased eruption rates. Amphibole temperatures during this time are relatively restricted (~850–1,000 °C). The crystal record presented here offers a time-transgressive view of an evolving, multi-tiered subvolcanic reservoir. Some crystals in AVC lavas are likely to be true phenocrysts, but the diversity of crystallization temperatures and pressures recorded by phases in individual AVC lavas suggests erupting magma extensively reams and accumulates crystals from disparate levels of the middle to upper crust.
机译：已经探测了来自长寿奥坎基尔查火山群（AVC）的熔岩的非晶体组合，以评估喷发前弧岩浆的压力和温度条件。在智利北部安第斯山脉中部，经历了长达一千一百万年的弧形岩浆旋涡，喷发了安第斯山脉至赤铁矿的AVC熔岩。热压法的目标相包括闪石，斜长石，辉石和Fe-Ti氧化物。总的来说，结晶度在1–7.5 kbar（〜25 km）的压力和〜680–1,110°C的温度下记录。闪石的压力估计范围约为1至5 kbar，辉石的压力范围约为3至7.5 kbar。辉石的温度在〜1,000–1,100°C的范围内紧密聚集，Fe–Ti氧化物的温度在〜750–1,000°C的范围内，闪石的温度在〜780–1,050°C的范围内。这些温度虽然稍高一些，但与先前发布的锆石温度范围大约为670-900°C很好。比较了两个不同的Fe-Ti氧化物温度计（Andersen和Lindsley 1985； Ghiorso和Evans 2008），并取得了一致。我们还比较了闪石和闪石-斜长石热气压计（Ridolfi等人，2010； Holland和Blundy，1994； Anderson和Smith，1995），但解决方案并不一致。在我们使用多个温度计的样品中，辉石的温度估算值始终最高，锆石的温度估算值最低，而Fe-Ti氧化物和闪石的温度估算值介于两者之间。在AVC活动的中间阶段（〜5-3 Ma）观察到最高的Fe-Ti氧化物和锆石温度，这是与喷发率增加相关的时间。这段时间内的闪石温度受到相对限制（〜850–1,000°C）。此处提供的晶体记录提供了一个演化的多层次火山岩储层的时移视图。 AVC熔岩中的某些晶体很可能是真正的角晶，但各个AVC熔岩中各相所记录的结晶温度和压力的多样性表明，岩浆大量喷出，并从中壳到上地壳的不同水平积聚了晶体。

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