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首页> 外文期刊>Contributions to Mineralogy and Petrology >A mineral and cumulate perspective to magma differentiation at Nisyros volcano, Aegean arc
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A mineral and cumulate perspective to magma differentiation at Nisyros volcano, Aegean arc

机译：矿物质和累积岩浆差异在尼西罗斯火山的差异，爱琴海弧

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摘要

Lavas and pyroclastic products of Nisyros volcano (Aegean arc, Greece) host a wide variety of phenocryst and cumulate assemblages that offer a unique window into the earliest stages of magma differentiation. This study presents a detailed petrographic study of lavas, enclaves and cumulates spanning the entire volcanic history of Nisyros to elucidate at which levels in the crust magmas stall and differentiate. We present a new division for the volcanic products into two suites based on field occurrence and petrographic features: a low-porphyricity andesite and a high-porphyricity (rhyo) dacite (HPRD) suite. Cumulate fragments are exclusively found in the HPRD suite and are predominantly derived from upper crustal reservoirs where they crystallised under hydrous conditions from melts that underwent prior differentiation. Rarer cumulate fragments range from (amphibole-)wehrlites to plagioclase-hornblendites and these appear to be derived from the lower crust (0.5-0.8 GPa). The suppressed stability of plagioclase and early saturation of amphibole in these cumulates are indicative of high-pressure crystallisation from primitive hydrous melts (>= 3 wt% -H2O). Clinopyroxene in these cumulates has -Al2O3 contents up to 9 wt% due to the absence of crystallising plagioclase, and is subsequently consumed in a peritectic reaction to form primitive, Al-rich amphibole (Mg# > 73, 12-15 wt% Al2O3). The composition of these peritectic amphiboles is distinct from trace element-enriched interstitial amphibole in shallower cumulates. Phenocryst compositions and assemblages in both suites differ markedly from the cumulates. Phenocrysts, therefore, reflect shallow crystallisation and do not record magma differentiation in the deep arc crust.
机译：牛斯罗斯火山（爱琴海弧，希腊）的熔岩和发热产品举办各种异种甾脂肪，并累积了一个独特的窗口，进入了最早的岩浆差异的阶段。本研究提出了一种详细的岩土学研究熔岩，环绕和累积跨越尼西罗斯的整个火山历史，以阐明地壳岩浆摊位和区分的水平。我们为火山产品的新部门展示了基于现场发生和岩体特征的两套套房：低斑点安特，高孔隙度（Rhyo）Dacite（HPRD）套件。累积片段专门发现在HPRD套件中，主要来自上层地壳储存器，其中它们在散热中在含水条件下结晶，从而进行了经历了先前分化的熔体。 RARER累积碎片范围从（倒角）WEHRLITES到Plagioclase-Hornblendites，这些似乎源自下地壳（0.5-0.8GPa）。在这些累积中抑制蛋白酶的抑制稳定性和锥形倍铬的早期饱和度标准从原始含水熔体（> = 3wt％-H2O）的高压结晶。这些累积的Clowocogexene由于没有结晶型镀锌酶而具有-Al2O3含量高达9wt％，随后在包层中消耗以形成原始的，富含型锥形态（Mg＃> 73,12-15wt％Al 2 O 3）。 。这些包晶倍倍硼的组成与较浅的累积中的痕量元素富集的间质倍苯胺不同。两种套房中的Phenocryst组合物和组合物从累积中显着不同。因此，苯杂交反射浅结晶，并且不会在深弧外壳中记录岩浆分化。

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