Heating Stage Experimental Study of Melt Inclusions in Feldspars from Three Holocene Eruptions of Changbaishan Tianchi Volcano     

Li Ni  Nicole Métrich  Fan Qicheng 《中国地震研究》2008,22(2):153-163

There occurred several eruptions from Changbaishan Tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. （Eruption Ⅰ ）, gray comenditic pumice and pyroclastic flow of - 1000a B.P. （ Eruption II, i.e. the millennium explosive eruption）, black trachy pumice and welded tuff of - 300a B.P. （ Eruption Ⅲ ） respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption H, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that （ 1 ） small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; （2） homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and （3） a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating.  相似文献   

安徽省风化花岗岩资源的开发与利用     

刘闯  王志勇 《地质与勘探》2000,36(6):4-5

介绍了安徽省风化花岗岩资源,通过提取钾长石矿物原料,生产免烧砖的改良土壤等途径,更好地解决开发利用风化花岗岩资源的问题,提出合理开发和保护风化花岗岩资源的建议。  相似文献   

脉宽调制型数字温度表     

张宏富 《成都信息工程学院学报》2000,15(2):142-144

选择线性热敏电阻组成的脉宽电路 ,将脉宽作为控制计数的时间 ,由晶振产生某一标准频率的脉冲信号 ,通过分频以及计算译码驱动送显示。可直接显示温度数字。该设计省去 A/ D转换器 ,结构简单 ,成本低廉 ,灵敏度高 ,稳定可靠 ,使用方便。  相似文献   

熔体包裹体对长白山天池火山千年大喷发的指示意义   总被引：2，自引：2，他引：0  

李霓  樊祺诚  孙谦  盘晓东 《岩石学报》2008,24(11):2604-2614

长白山天池火山在全新世曾有过几次喷发,其中距今约1000年发生过大规模布里尼式爆炸喷发（即“千年大喷发”）,其喷发产物——灰白色碱流质浮岩和喷发柱垮塌形成的火山碎屑流分布范围极广,除长白山区外,在朝鲜半岛和日本北部也有大量浮岩降落和堆积。根据野外较大范围的系统采样、镜下观察和测试分析,在天池火山千年大喷发产物的碱性长石晶屑中发现了两组颜色、形态、化学成分迥异的“火口组”和“圆池组”熔体包裹体,对揭示天池火山千年大喷发的成因具有重要意义。根据电子探针分析结果,“火口组”熔体包裹体成分为英安岩和粗面英安岩,寄主晶多为透长石;“圆池组”熔体包裹体成分为粗面英安岩和流纹岩,寄主晶为歪长石。相对“火口组”熔体包裹体,“圆池组”包裹体具有高SiO2、高H2O和高Cl含量的特点,化学成分也更为演化,可能是天池火山千年大喷发时岩浆结晶分异后期的产物。两组包裹体的存在为千年大喷发前的层状地壳岩浆房和成分并非单一提供了证据,它们可能是在同次大喷发的不同序列中喷出的。由于地幔岩浆注入地壳岩浆房,导致不同层位岩浆的扰动和混合作用,因挥发分出溶在岩浆房最顶部形成挥发分梯度和过饱和,最终触发了天池火山的千年大喷发,对当时的气候环境造成过较大影响。  相似文献   

"Water Consumption" in the Diagenetic Stage and Its Petroleum Geological Significance     

ZHANG Shanwen 《《地质学报》英文版》2008,82(3)

Inspired from the anomaly of low pressure in the middle and deep reservoir of the Paleogene in the Jiyang depression, this paper theoritically discusses"waterconsumption"of the principal mineral alteration during the diagenetic stage. The preliminary research result shows that "water consumption" of mineral alteration in the diagenetic stage can make formation water greatly decrease. Relevant formations will be in the stage of low pressure without supply of exterior liquid. Pressure differences between the relevant formations and wall rocks make hydrocarbons enter easily to form the effective reservoir.  相似文献   

乌拉山金矿钾长石的标型性及其与金矿化关系   总被引：6，自引：0，他引：6  

边秋娟  张汉凯 《黄金地质》1997,3(3):8-15

在对乌拉山石英－钾长石脉型这一国内外尚不多见的新类型金矿床的野外观察和室内镜下研究的基础上，通过选择性地对其主要矿物钾长石进行电子探针分析，Ｘ射线粉晶衍射分析，红２外吸收光谱测定及可见光吸收光谱分析，系统详尽地了钾长石的产状，形态，化学成分，结构态及可见光吸收光谱特征，提取了作为找寻石英－钾长石脉型金矿床的重要矿物学标志，并进一步探讨了钾长石与金矿化的关系。  相似文献   

内蒙古正镶白旗碎斑熔岩长石特征及其岩石学意义   总被引：1，自引：0，他引：1  

赖绍聪  徐海江 《矿物学报》1992,12(1):26-35

正镶白旗碎斑熔岩是一种特殊成因的火山岩,是岩浆沿火山通道侵出地表的产物。碎斑熔岩中钾长石主要为低透长石、高正长石、中正长石和中正微长石;斜长石则以更长石为主,其有序度低,指示了岩石高温火山成因的特征。从岩体边缘相到中心相至根部相,长石类型、化学成分和有序度具有一定的变化规律,反映了岩体不同岩相带成岩条件的差异性。  相似文献   

黑龙江省五大连池、科洛、二克山火山群富钾火山岩中的浅色矿物     

邱家骧  廖群安 《地球科学》1990,(4)

本区富钾火山岩中浅色矿物有碱性长石、白榴石和霞石。碱性长石主要为钠透长石、钙歪长石,少数为钙钠透长石和歪长石,其光性变化与长石的地质时代和长石内部的隐条纹结构有关。白榴石的成分及产出方式主要与岩石中的SiO_2含量有关,SiO_2不饱和程度大的白榴苦橄岩的白榴石贫SiO_2;而SiO_2不饱和程度低的白榴碧玄岩和白榴玄武岩中,白榴石富SiO_2而稍贫K_2O+Na_2O,仅见于过渡相,而中心相由于水压较高和近于平衡的结晶条件,白榴石不能晶出,或先晶出后又与熔体反应形成碱性长石。  相似文献   

On the dose dependency of the bleachable and non-bleachable components of IRSL from K-feldspar: Improved procedures for luminescence dating of Quaternary sediments     

《Quaternary Geochronology》2013

The infrared (IR) stimulated luminescence (IRSL) and post-IR IRSL (pIRIR) signals from K-feldspar can, for convenience, be divided into two components, bleachable and ‘non-bleachable’, where the latter corresponds to the ‘residual’ signal observed in sunlight-bleached samples. In this paper, we examine the non-bleachable component of IRSL of K-feldspar for several sedimentary samples from across Eurasia. We observed a large variability in the residual doses among these samples after prolonged exposure to sunlight. By employing multiple elevated temperature (MET) IR stimulations at 50–300 °C, we show that the residual dose increases systematically with stimulation temperature, attaining values as high as ∼50 Gy at 300 °C, even after several hours to tens of hours of exposure to unfiltered sunlight. We examined two samples in detail and found that the bleachable and non-bleachable components produced different dose response curves. Pulse annealing studies showed that the non-bleachable component is more stable than the bleachable component, suggesting that a preheat procedure cannot eliminate the non-bleachable component. Additional experiments revealed that the non-bleachable component is dose dependent. Owing to this dose dependency, we demonstrate mathematically and empirically that the simple subtraction of a residual dose from the measured equivalent dose (D_e) – which is the most common approach employed (if any residual dose is subtracted at all) – will result in underestimation of the actual D_e. We present a method to correct for the dose dependency of the residual dose, which can improve the accuracy of either MET-pIRIR or pIRIR age estimates for samples in which the non-bleachable component represents a significant fraction of the measured signals.  相似文献   

Garnet–clinopyroxene intermediate granulites in the St. Leonhard massif of the Bohemian Massif: ultrahigh‐temperature metamorphism at high pressure or not?     

M. RACEK  P. &#;TÍPSKÁ  R. POWELL 《Journal of Metamorphic Geology》2008,26(2):253-271

Garnet–clinopyroxene intermediate granulites occur as thin layers within garnet–kyanite–K–feldspar felsic granulites of the St. Leonhard granulite body in the Bohemian Massif. They consist of several domains. One domain consists of coarser‐grained coexisting ternary feldspar, clinopyroxene, garnet, quartz and accessory rutile and zircon. The garnet has 16–20% grossular, and the clinopyroxene has 9% jadeite and contains orthopyroxene exsolution lamellae. Reintegrated ternary feldspar and the Zr‐in‐rutile thermometer give temperatures higher than 950 °C. Mineral equilibria modelling suggests crystallization at 14 kbar. The occurrence and preservation of this mineral assemblage is consistent with crystallization from hot dry melt. Between these domains is a finer‐grained deformed matrix made up of diopsidic clinopyroxene, orthopyroxene, plagioclase and K‐feldspar, apparently produced by reworking of the coarser‐grained domains. Embedded in this matrix, and pre‐dating the reworking deformation, are garnet porphyroblasts that contain clinopyroxene, feldspar, quartz, rutile and zircon inclusions. In contrast with the garnet in the coarser‐grained domains, the garnet generally has >30% grossular, the included clinopyroxene has 7–27% jadeite and the Zr content of rutile indicates much lower temperatures. Some of these high‐grossular garnet show zoning in Fe/(Fe + Mg), decreasing from 0.7 in the core to 0.6 and then increasing to 0.7 at the rim. These garnet are enigmatic, but with reference to appropriate pseudosections are consistent with localized new mineral growth from 650 to 850 °C and 10 to 17 kbar, or with equilibration at 20 kbar and 770 °C, modified by two‐stage diffusional re‐equilibration of rims, at 10–15 and 8 kbar. The strong pervasive deformation has obscured relationships that might have aided the interpretation of the origin of these porphyroblasts. The evolution of these rocks is consistent with formation by igneous crystallization and subsequent metamorphism to high‐T and high‐P, rather than an origin by ultrahigh‐T metamorphism. Regarding the petrographic complexity, combination of the high grossular garnet with the ternary feldspar to infer ultrahigh‐T metamorphism at high pressure is not justified.  相似文献