共查询到20条相似文献，搜索用时 371 毫秒
1.
西昆仑山普鲁新生代火山岩中包体的发现及其地质意义 总被引：6，自引：1，他引：6
报道了在西昆仑用于田县南普鲁火山岩首次发现的包体的产出特下与矿物组成特征，提出其包体为岩浆在高位岩浆房中分离结晶作用形成的堆积相，并估算了其原始岩浆的成分特征。结果表明：其原始岩浆和处于同一火山带的康西瓦火山岩相似，暗示了它们来自于同一源区。但在高位岩浆房中，随着分离结晶作用的进行。岩浆的温度和氧逸度逐渐降低。 相似文献
2.
西昆仑普鲁新生代火山岩的矿物化学特征及其对岩浆演化过程的约束 总被引：2，自引：0，他引：2
对西昆仑普鲁新生代火山岩的矿物学进行了系统的研究。结果表明：该地区火山岩主要由橄榄石、单斜辉石和斜长石组成,并有少量的斜方辉石、黑云母、角闪石、碱性长石和铁钛氧化物。其矿物学特征指示了岩浆的性质有点类似于碱性岩浆,但与典型的碱性玄武岩又有明显的区别,属于橄榄安粗岩系列。利用橄榄石-熔体平衡原理估算了进入高位岩浆房中的熔体的MgO含量约为6．2％,Mg^#为0．57,说明其不是地幔熔融形成的原始岩浆,而是经历了深部岩浆房的分离结晶过程。由单斜辉石估算的高位岩浆房的深度约7～9km。岩浆在高位岩浆房中发生了较长时间的强烈分离结晶作用,分离结晶相主要为橄榄石、单斜辉石和斜长石以及少量的斜方辉石、黑云母、角闪石、碱性长石和铁钛氧化物。不同时期形成的铁钛氧化物指示了分离结晶过程由相对高温高氧逸度向相对低温低氧逸度演化。与此相对照的是岩浆在深部岩浆房中可能只发生了橄榄石和辉石等铁镁矿物的分离结晶作用,且分异作用时间较短。深部岩浆房可能存在于岩石圈地幔或壳幔过渡带中,岩浆由深部岩浆房上升到高位岩浆房中的过程是近绝热的,从浅部岩浆房到地表是快速上升的过程。 相似文献
3.
辽西义县盆地火山岩的基本特征及其成因探讨 总被引：17，自引：0，他引：17
通过对辽西义县盆地火山岩的岩石学、矿物学以及地球化学特征的研究，指出本区火山岩属于一套弱碱性、普通型的火山岩系列．通过热力学计算以及对岩石结构和动力学的分析，表明原始岩浆来自上地幔（约６７ｋｍ），并在约１７ｋｍ处（上下地壳附近）形成高位岩浆房．在高位岩浆房中，由于岩浆的双扩散对流作用，发生了伴随有分离结晶作用的液相分异作用，而同化混染作用则发生于岩浆演化的早期。喷出的岩浆成分受断裂切过高位岩浆房的相对位置的控制。 相似文献
4.
The volcanic rock series on the Fildes Peninsula is the product of the later subduction of the Pacific platebeneath the Antarctic plate. It consists mainly of basalt, basaltic andesite and andesite with minor dacite. Itsisotopic ages range from 64.6±1 to 43±2 Ma, belonging to Palaeocene to Eocene. Volcanism in the area maybe divided into two phases. The contents of major oxides, rare earth elements (REE) and trace elements in vol-canic rocks formed in different phases show regular changes, which are mainly related to the rock associationsof these phases. Isotope geochemical studies indicate that the primitive magma in the area originating by par-tial melting in the upper mantle underwent fractional crystallization and ascended to the high-level (shallow)magma chamber. Before eruption the primitive basalt-andesitic magma was subjected to differentiation in thehigh-level magma chamber, forming zones of derivative magmas of different compositions. In various phasesmagma-conducting faults experienced periodic extension and cut through various derivative magma zones indifferent parts of the peninsula, leading to the eruption of magmas of different compositions on the surface andthe formation of volcanic rock associations of corresponding compositions. 相似文献
5.
峨眉山大火成岩省出露有少量酸性火山岩,它们与基性火山岩共生,表现出双峰式的特征,为研究峨眉山地幔柱晚期岩浆活动提供了重要的窗口。本文通过对双峰式火山岩主、微量元素和斑晶电子探针分析研究表明,基性火山岩属于碱性玄武岩,酸性火山岩主要由粗面岩组成;相对玄武岩,粗面岩中MgO、Fe2O3、P2O5、TiO2、CaO含量明显降低;粗面岩与玄武岩具有相互平行的REE配分模式,但粗面岩出现明显的Eu负异常,以及Sr、Ti等元素的强烈亏损;粗面岩与玄武岩具有同源的特征,通过稀土元素模拟计算表明粗面岩可以由玄武质岩浆经过80%分离结晶作用(辉石、斜长石和Fe-Ti氧化物)而形成。在峨眉山大火成岩省晚期出现双峰式火山岩,可能与地幔柱活动晚期岩浆供给少,在地壳岩浆房中停留时间长,岩浆发生强烈分离结晶作用有关。 相似文献
6.
处于浙-赣火山岩带东北缘的湖(州)-安(吉)盆地内的火山岩/潜火山岩从中性到酸性,中间没有明显的成分间断,以中酸性—酸性组分占绝对优势,中性组分相对较少,缺少基性组分,代表一套连续的中性—酸性岩浆系列。岩石化学总体表现为富碱和高钾的特征,中性岩属橄榄玄粗岩系列,中酸性—酸性岩类属高钾钙碱性系列。盆地内的火山岩在地球化学上均表现为富集大离子亲石元素和轻稀土元素,而高场强元素Nb、Ta、Ti等则有一定程度的亏损。火山岩中主量和微量元素的变异规律揭示分离结晶作用是盆地内岩浆演化的主要机理,但岩浆演化的不同阶段分离的矿物相有所差异,斜长石自始至终都是分离结晶的重要矿物相,在中性—中酸性岩浆演化阶段,角闪石可能也是重要的分离矿物,而中酸性—酸性岩中钾长石和黑云母的分离结晶也起着重要影响。本文所作的精确定年结果表明,盆地内三期火山活动产物的LA-ICPMS锆石U-Pb年龄在误差范围内几乎一致,介于128~130 Ma之间,指示盆地内主要火山活动持续的时间很短。另外测得粗安岩集块的SHRIMP锆石U-Pb年龄为136±1 Ma,可能意味着该盆地初期有少量偏基性的火山活动。推测湖安火山岩盆地发育于活动大陆边缘的后造山环境,岩浆的形成可能受控于岩石圈的拆沉或俯冲板片的断落,母岩浆主要是由镁铁质下地壳物质部分熔融形成的,几乎没有地幔物质的参与,所形成的安山质-英安质岩浆在浅部岩浆房中发生过强烈的分异演化。 相似文献
7.
南澜沧江结合带火山岩岩浆成因——洋脊洋岛与弧岩浆作用的性质 总被引：10，自引：1，他引：9
在对滇西南昌宁—孟连带石炭—二叠纪火山岩和南澜沧江带二叠—三叠纪火山岩的微量元素和稀土元素研究的基础上,划分了岩浆作用类型和岩浆演化系列,探讨了岩浆源区成分特点。昌宁—孟连带玄武质岩浆的演化主要受部分熔融和分离结晶作用控制;这些岩浆可以划分为３个岩浆演化系列：（１）稀土曲线平坦型的洋脊型拉斑玄武岩浆演化系列,其岩浆起源于亏损型地幔;（２）稀土曲线中等富集型的准洋脊型拉斑玄武岩浆演化系列,其岩浆起源于过渡型地幔;（３）稀土曲线强烈富集型的洋岛型碱性玄武岩浆演化系列,其岩浆起源于富集型地幔。南澜沧江带弧火山岩的岩浆成因主要受分离结晶作用控制,也可以划分为３个岩浆演化系列：（１）二叠纪低钾拉斑—中钾钙碱性岩浆演化系列;（２）中南段的晚三叠世低钾拉斑—中钾钙碱性岩浆演化系列;（３）北段的晚三叠世钾玄岩—高钾钙碱性岩浆演化系列 相似文献
8.
吉林红旗岭1号和7号岩体中含矿超镁铁质岩的矿物化学特征:对岩浆演化过程以及铜镍硫化物矿床形成机制的约束 总被引：2，自引：1，他引：1
本文对吉林红旗岭1号和7号岩体中含矿超镁铁质岩的主要造岩矿物进行了详细研究。两岩体的主要造岩矿物为贵橄榄石、古铜辉石、单斜辉石、斜长石、角闪石和金云母。岩浆的暗色矿物结晶顺序为:橄榄石→斜方辉石→单斜辉石→角闪石→黑云母,与镜下实际观察一致,是岩浆在不同深度结晶的产物。原始岩浆来自上地幔,两岩体进入高位岩浆房中的熔体的MgO含量分别13.98%和14.22%、Mg#值分别为72.22和71.05,为含水的高镁的苦橄质玄武岩浆。深部岩浆房深度距地表约26～27km,岩浆房内的结晶温度介于1280～1379℃之间,即结晶于下地壳中。岩浆由深部上升到高位(浅部)岩浆房中的过程是近绝热的,也是快速完成的。岩浆可能经历了两次岩浆房的演化过程,岩浆在上升到高位岩浆房之前,在深部曾经历了较短时间的橄榄石和少量辉石的分离结晶作用;但在高位岩浆房中混染了地壳物质,与此同时,还经历了同源岩浆混合作用以及岩浆过冷却作用,这些都有利于岩浆体系中成矿元素含量增高以及硫达到饱和状态,使金属硫化物熔离并晶出,从而使岩体发生铜镍矿化作用。 相似文献
9.
杭州南部新元古界青白口系上墅组火山岩,由基性岩和酸性岩组成,缺乏SiO2在57×10-2～68×10-2的中性及中酸性成分,构成一套双峰式火山岩组合。基性火山岩与酸性火山岩的稀土元素和微量元素特征存在明显差异,表明酸性火山岩并不是由基性岩浆分离结晶产生,而是分别由不同的源区熔融形成,基性火山岩起源于亏损程度较低的地幔或来源于亏损地幔的岩浆受到陆壳物质的混染,酸性火山岩主要由上地壳经不同程度的部分熔融而形成,其形成的构造环境为陆内至陆缘张裂环境。上墅组双峰式火山岩的形成,是华南Rodinia超大陆裂解事件的岩石学记录,揭示了华南Rodinia超大陆裂解始于青白口纪。 相似文献
10.
北淮阳晚侏罗世金刚台组火山岩岩石化学和地球化学特征及构造环境 总被引：2，自引：0，他引：2
晚侏罗世金刚台组火山岩分布在北淮阳中生代火山岩带的中部，主要岩石类型为火山碎屑岩类。据岩石化学成分，金刚台组火山岩可划分为安山质、英安质、粗面英安质和流纹质几种类型，并属于高钾钙碱性系列。其岩石化学和地球化学显示岩浆起源于下地壳，并经历了正常的分离结晶作用，有轻微的混染，岩浆开始结晶温度为９３６～１１２２℃，压力约为０２４ＧＰａ。据岩石地球化学方法判别，其构造环境具有类似于火山弧的特点，结合区域构造动力学背景分析，其形成可能与大别山造山带后期的陆内俯冲而引起的陆壳增厚有关 相似文献
11.
银山地区火山岩－次火山岩由流纹岩、流纹英安斑岩、英安质熔岩、英安斑岩和粗面安山斑岩组成,喷发和侵入存在着反序特征．通过各种物理化学方法确定了岩浆房中存在的化学成分和温度、密度、粘度梯度．建立了以英安质岩浆为主,顶部有一层富ＳｉＯ２、富Ｋ的流纹质岩浆,底部为少量粗面安山质岩浆的带状岩浆房．岩浆演化及带状岩浆房的形成是分离结晶、同化混染、岩浆对流和边界层机制共同作用的结果． 相似文献
12.
长白山天池火山双岩浆房岩浆作用与互动式喷发 总被引：6，自引：0，他引：6
广义的长白山火山在我国境内包括天池火山、望天鹅火山、图们江火山和龙岗火山,是我国最大的第四纪火山岩分布区。长白山各个火山区的火山活动具有此起彼伏的穿时性特征,天池火山之下地壳和地幔两个岩浆房具有上下呼应、互动式喷发之特点。一方面来自地幔的钾质粗面玄武岩浆直接喷出地表,在天池火山锥体内外形成诸多小火山渣锥;另一方面钾质粗面玄武岩浆持续补给地壳岩浆房,发生岩浆分离结晶作用和混合作用,形成双峰式火山岩特征并触发千年大喷发。西太平洋板块俯冲-东北亚大陆弧后引张是长白山天池火山喷发的动力学机制。 相似文献
13.
冲绳海槽是一个处于弧后扩张作用早期的年轻的弧后盆地,是研究弧后扩张作用早期盆地演化和壳幔过程的天然实验室.随着调查研究工作的逐步展开和深入,也发现了一些新的、重要的、亟待解决的科学问题,而火山岩岩石系列归属的厘定又是其他研究工作的基础.在系统收集和整理迄今已有冲绳海槽火山岩资料的基础上,结合近期分析测试数据, 对冲绳海槽火山岩的岩石系列归属进行了重新厘定,探讨了火山岩的构造环境指示意义和浮岩与玄武岩之间的成因联系.研究结果表明:冲绳海槽火山岩分布具有以基性玄武岩和酸性(流纹)英安岩为主的双峰式特征,中性火山岩稀少,基性的玄武岩属于亚碱性系列的橄榄拉斑玄武岩,酸性浮岩可归属为亚碱性岩系的流纹英安岩或流纹岩;在构造环境判别上,冲绳海槽玄武岩表现出大洋中脊和岛弧构造环境的特点,既有别于大洋中脊扩张中心,也有别于成熟型弧后盆地,呈现出弧后早期扩张阶段盆地独特的构造环境特征;广泛分布于冲绳海槽的酸性浮岩表现出一定的岛弧环境的特点;酸性浮岩与玄武岩具有同源性,酸性岩是基性的玄武质岩浆经不同程度结晶分异和同化混染作用的产物. 相似文献
14.
《International Geology Review》2012,54(9):850-863
Petrographic, major-oxide, and trace-element data are presented for the Yozgat volcanics. These rocks range in composition from basalts through basaltic andesites and andesites to dacites. Major-oxide variations are largely explicable in terms of fractional crystallization, involving removal of observed phenocrysts and microphenocrysts. However, complex zoning patterns and resorbtion phenomena shown by phenocrysts in these lavas, and observed epitaxitic pyroxene growth around quartz xenocrysts imply that they are hybrids formed by a mixing process. In addition, observed enrichments in crustal elements such as K, Rb, Ba, Sr, and P provide clear evidence for the crustal assimilation of granitoid and metasedimentary xenoliths. The following model is suggested for the evolution of the Yozgat volcanics. The primitive magma underwent fractionation in an intracrustal magma chamber to yield more evolved liquids. Influx of hot, primitive magma into the magma chamber promoted vigorous convection-crustal assimilation and eruption of the volcanic rocks in the study area. 相似文献
15.
塔什库尔干新生代碱性杂岩造岩矿物化学成分及成因意义 总被引：1，自引：0，他引：1
新疆塔什库尔干碱性杂岩体主要由苦子干碱性正长岩体和卡日巴生碱性花岗岩体组成，是帕米尔地区最大的新生代碱性杂岩体。本文在岩相学和矿物化学的基础上，着重研究了苦子干岩体主要造岩矿物的种属、共生关系和结晶顺序。研究表明，苦子干岩体中的不同岩石类型系同源岩浆演化的产物；岩浆在整个演化过程中平衡结晶作用占主导，分离结晶作用的影响极小。据岩浆房中矿物结晶时的温度和压力条件、矿物的结晶特征及演化趋势，推测岩浆上升速度较快，侵位较浅。 相似文献
16.
The Vandfaldsdalen macrodike, which lies in the Skaergaard region of East Greenland, is a remarkably zoned fossil magma chamber, with a granophyric cap overlying cumulate gabboros. The intrusion is distinctly bimodal, with a large compositional discontinuity at the contact between the gabbro and granophyre. Although the exposed part of the macrodike is in contact with Tertiary basalts and sediments, the granophyre originated by assimilation of xenoliths derived from the underlying Archean basement. Sr and Nd isotopic ratios throughout the cumulate sequence are remarkably similar, indicating insignificant contamination of the gabbro by the granophyre. Modelling of the compositional effects of cooling and crystallization indicate that the cumulate pile resulted from fractional crystallization, with the complicating effects of trapped liquid and post-cumulus fractionation. The uppermost rocks in the mafic part, of the chamber (SiO2=62%; FeO*=12.4%) resulted from about 85% fractional crystallization. A transgressive sill of strongly fractionated magma (SiO2=67%; FeO*=8.8%) formed from extracted intercumulus liquid that was the result of 90% fractional crystallization of the original magma. Mass-balance indicates that typical granophyre is made up of about 75% dissolved xenoliths, by weight, and 25% mantle-derived basaltic magma. The magmas were not measurably affected by material exchange across the interface between the gabbro and granophyre. This magma chamber evolved by both assimilation and fractional crystallization, but the residual liquids formed by fractional crystallization were unaffected by assimilation. Heat exchange between were unaffected by assimilation. Heat exchange between the two parts of the chamber was obviously important, but there was insignificant material exchange. The inability of fractional crystallization and assimilation to affect the same liquid is related to the dynamic behavior of this particular magma chamber, particularly the buoyancy of granophyre relative to evolving tholeiitic magma. 相似文献
17.
Geochemistry of intermediate to siliceous volcanic rocks of the Rooiberg Group, Bushveld Magmatic Province, South Africa 总被引：1，自引：1，他引：1
P. Buchanan W. Reimold C. Koeberl F. Kruger 《Contributions to Mineralogy and Petrology》2002,144(2):131-143
The volcanic Rooiberg Group represents the earliest phase of Bushveld-related magmatism and comprises, in some areas, the floor and roof rocks of the mafic-ultramafic intrusive units of the Bushveld Complex. The lower to middle Dullstroom Formation is composed of two interbedded series of low Ti and high Ti volcanic strata, which are predominantly basaltic andesites. Volcanic units above these strata range from andesites to dacites in the upper Dullstroom Formation and to predominantly rhyolites in the overlying Damwal and Kwaggasnek Formations. Compositional data suggest that these intermediate to siliceous volcanic rocks are petrogenetically related to the low Ti volcanic suite and suggest that the low Ti magmas resided in a shallow magma chamber where they experienced fractional crystallization and assimilation of crustal material. In contrast, the high Ti volcanic suite is petrogenetically unrelated. These data confirm previous suggestions that Bushveld-related magmas experienced significant amounts of assimilation of continental crust. 相似文献
18.
我国东北小古里河-科洛-五大连池-二克山火山带钾质矿物成因及地质意义 总被引：3，自引：2，他引：1
东北黑龙江小古里河-科洛-五大连池-二克山火山岩带是我国近代保存最好的火山群之一,此带火山岩的岩石化学特点全都强碱富钾,K2O/Na2O>1.2,属于一套高钾过碱性火山岩。通过对东北钾质火山岩及金云母橄榄岩地幔捕虏体中钾质矿物金云母、白榴石的成分、结晶环境与岩浆成分及来源关系的研究,认为在岩石圈伸展构造背景下,地幔金云母橄榄岩的低度部分熔融形成钾质岩浆,钾质岩浆上升到地壳浅部经历了白榴石的结晶作用。岩浆演化晚期,因钾质矿物大量晶出导致岩浆相对富钠而出现他形霞石和方钠石等填隙矿物。火山岩及地幔捕虏体中富挥发分矿物金云母、白榴石、磷灰石、霞石和方钠石还提供了钾质岩浆富含H2O、F、Cl、P等挥发分的证据。 相似文献
19.
《International Geology Review》2012,54(7):595-610
The Kale (Gumushane) volcanic rocks crop out in the southern zone of the eastern Pontide arc, and consist mainly of agglomerate, andesite, minor basalt, and tuff associated with sediments (limestone, marl, siltstone, sandstone) deposited in a shallow basin environment. The volcanites show mainly porphyritic, hyalo-porphyritic, and rare fluidal and glomeroporphyritic textures. These volcanic rocks consist predominantly of plagioclase, augite, hornblende, and lesser biotite, magnetite, and quartz, and secondary products of chloritization, carbonation, sericitization, and epidotization. In general, they show disequilibrium textures, possibly reflecting magma-mixing processes. The volcanic rocks are mainly calc-alkaline in composition, and show moderate potassium enrichment. Most of the major- and trace-element variations reflect the significant role of fractional crystallization during the evolution of the volcanic suite. The fractionating phases are dominantly hornblende and augite, minor plagioclase, and magnetite. The rocks have high LILE and LREE enrichments, but are relatively depleted in HFSE relative to MORB. Moreover, incompatible trace-element distributions show similarities to those of an E-type MORB source. The rocks have moderately fractionated REE patterns with (La/Lu)N = 2–12. Geochemical data suggest that the volcanites evolved by shallow-level fractional crystallization and magma-mixing contamination of a parental magma derived from metasomatized upper mantle by partial melting after thickening of the Pontide arc during the Paleocene-Eocene. Furthermore, differentiation took place in a magma chamber situated in the thickened arc crust within an extensional tectonic regime. 相似文献
20.
Chemical and thermal zonation in a mildly alkaline magma system Infiernito Caldera,Trans-Pecos Texas
Christopher D. Henry Jonathan G. Price Rebecca C. Smyth 《Contributions to Mineralogy and Petrology》1988,98(2):194-211
Postcollapse lavas of the Infiernito caldera grade stratigraphically upward from nearly aphyric, high-silica rhyolite (76% SiO2) to highly prophyritic trachyte (62% SiO2). Plagioclase, clinopyroxene, orthopyroxene, magnetite, ilmenite, and apatite occur as phenocrysts throughout the sequence. Sanidine, biotite, and zircon are present in rocks with more than about 67% SiO2. Major and trace elements show continuous variations from 62 to 76% SiO2. Modeling supports fractional crystallization of the observed phenocrysts as the dominant process in generating the chemical variation.Temperatures calculated from coexisting feldspars, pyroxenes, and Fe-Ti oxides agree and indicate crystallization from slightly more than 1100° C in the most mafic trachyte to 800° C in high-silica rhyolite. The compositional zonation probably arose through crystallization against the chilled margin of the magma chamber and consequent rise of more evolved and therefore less dense liquid.Mineral compositions vary regularly with rock composition, but also suggest minor mixing and assimilation of wall rock or fluids derived from wall rock. Mixing between liquids of slightly different compositions is indicated by different compositions of individual pyroxene phenocrysts in single samples. Liquid-solid mixing is indicated by mineral compositions of glomerocrysts and some phenocrysts that apparently crystallized in generally more evolved liquids at lower temperature and higher oxygen fugacity than represented by the rocks in which they now reside. Glomerocrysts probably crystallized against the chilled margin of the magma chamber and were torn from the wall as the liquid rose during progressive stages of eruption. Assimilation is indicated by rise of oxygen fugacity relative to a buffer from more mafic to more silicic rocks.Calculation of density and viscosity from the compositional and mineralogical data indicates that the magma chamber was stably stratified; lower temperature but more evolved, thus less dense, rhyolite overlay higher temperature, less evolved, and therefore more dense, progressively more mafic liquids. The continuity in rock and mineral compositions and calculated temperature, viscosity, and density indicate that compositional gradation in the magma chamber was smoothly continuous; any compositional gaps must have been no greater than about 2% SiO2. 相似文献