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111.
Geochemical modeling of magma mixing allows for evaluation of volumes of magma storage reservoirs and magma plumbing configurations.
A new analytical expression is derived for a simple two-component box-mixing model describing the proportions of mixing components
in erupted lavas as a function of time. Four versions of this model are applied to a mixing trend spanning episodes 3–31 of
Kilauea Volcano’s Puu Oo eruption, each testing different constraints on magma reservoir input and output fluxes. Unknown
parameters (e.g., magma reservoir influx rate, initial reservoir volume) are optimized for each model using a non-linear least
squares technique to fit model trends to geochemical time-series data. The modeled mixing trend closely reproduces the observed
compositional trend. The two models that match measured lava effusion rates have constant magma input and output fluxes and
suggest a large pre-mixing magma reservoir (46±2 and 49±1 million m3), with little or no volume change over time. This volume is much larger than a previous estimate for the shallow, dike-shaped
magma reservoir under the Puu Oo vent, which grew from ∼3 to ∼10–12 million m3. These volumetric differences are interpreted as indicating that mixing occurred first in a larger, deeper reservoir before
the magma was injected into the overlying smaller reservoir.
Electronic Supplementary Material Supplementary material is available at and is accessible for authorized users. 相似文献
112.
云南麻栗坡新寨锡矿物化探异常特征 总被引:3,自引:0,他引:3
新寨锡矿是物化探扫面发现的大型锡石硫化物矽卡岩型矿床,高磁,高激电率,低电阻率异常,原生晕Sn,W,Cu,Zn,As,B,Ag,Cd,Be,Bi,In,F(Mo,Ge,Co)等元素异常,次生晕Sn,Cu,Zn,As,B等异常,总结地球物理化学特征,对滇东南寻找同类矿床具有重要指导意义。 相似文献
113.
青藏高原北羌塘新生代高钾钙碱岩系火山岩角闪石类型有痕量元素地球化学 总被引:12,自引:2,他引:12
利用电子探针和激光探针剥蚀系统(LA-ICP-MS)对北羌塘新第三纪高钾钙碱岩系英安岩中角闪石的主元素和微量、角闪石强烈富集Sc、Ti、V、Cr、Co、Ni等不相容亲铁元素,而相对亏损Th、U、Pb、Rb等强不相容的大离子亲石元素。稀土元素丰度高,且无Eu异常,批示北羌塘这套高钾钙碱岩系火山岩可能是青藏高原加厚的相当于榴辉岩相物质组成的下部陆壳脱水熔融的产物。 相似文献
114.
湘西南高涧群的地球化学特征及其意义 总被引:3,自引:0,他引:3
湘西南高涧群主要是一套浅变质沉积碎屑岩系,由变质泥岩、板岩和变质粉砂岩组成,原岩颗粒小。变质作用对岩石化学成分没有大的改变,岩石具有相近的风化蚀变指数(平均CIA=75)风化蚀变矿物主要为伊利石-白云母-蒙脱石组合。主要化学成分反映沉积物来源于中性和基性火成岩区。浅变质沉积岩中大多数微量元素亏损,元素Cu,Zn,Co,Ti,Cr等在研究区的南部和北部具有相似的共生组合。并且稀土元素的分布模式基本相同,稀土的总量与岩性有关。上述特点显示了高涧群沉积物来源相同,亲石元素共生组合相似;Au,Ag,As,Sb,Sr,Ba等存在一定的分异,Ba/Co比值,Sr/Ba比值和δCe值表明,它是主要在浅深海-深海相还原环境下的产物。 相似文献
115.
High-Mg potassic rocks from Taiwan: implications for the genesis of orogenic potassic lavas 总被引:15,自引:0,他引:15
Sun-Lin Chung Kuo-Lung Wang Anthony J. Crawford V. S. Kamenetsky Cheng-Hong Chen Ching-Ying Lan Chang-Hwa Chen 《Lithos》2001,59(4):153-170
Taiwan is an active mountain belt formed by oblique collision between the Luzon arc and the Asian continent. Regardless of the ongoing collision in central and southern Taiwan, a post-collisional extension regime has developed since the Plio–Pleistocene in the northern part of this orogen, and led to generation of the Northern Taiwan Volcanic Zone. Emplaced at 0.2 Ma in the southwest of the Volcanic Zone, lavas from the Tsaolingshan volcano are highly magnesian (MgO≈15 wt.%) and potassic (K2O≈5 wt.%; K2O/Na2O≈1.6–3.0). Whereas these basic rocks (SiO2≈48 wt.%) have relatively low Al2O3≈12 wt.%, total Fe2O3≈7.5 wt.% and CaO≈7.2 wt.%, they are extremely enriched in large ion lithophile elements (LILE, e.g. Cs, Rb, Ba, Th and U). The Rb and Cs abundances, >1000 and 120 ppm, respectively, are among the highest known from terrestrial rocks. In addition, these rocks are enriched in light rare earth elements (LREE), depleted in high field strength elements (HFSE), and display a positive Pb spike in the primitive mantle-normalized variation diagram. Their REE distribution patterns mark with slight Eu negative anomalies (Eu/Eu*≈0.90–0.84), and Sr and Nd isotope ratios are uniform (87Sr/86Sr≈0.70540–0.70551; 143Nd/144Nd≈0.51268–0.51259). Olivine, the major phenocryst phase, shows high Fo contents (90.4±1.8; 1σ deviation), which are in agreement with the whole rock Mg-values (83–80). Spinel inclusions in olivine are characterized by high Cr/Cr+Al ratios (0.94–0.82) and have compositions similar to those from boninites that originate from highly refractory peridotites. Such petrochemical characteristics are comparable to the Group I ultrapotassic rocks defined by Foley et al. [Earth-Sci. Rev. 24 (1987) 81], such as orogenic lamproites from central Italy, Span and Tibet. We therefore suggest that the Tsaolingshan lavas resulted from a phlogopite-bearing harzburgitic source in the lithospheric mantle that underwent a recent metasomatism by the nearby Ryukyu subduction zone processes. The lavas exhibit unique incompatible trace element ratios, with Rb/Cs≈8, Ba/Rb≈1, Ce/Pb≈2, Th/U≈1 and Nb/U≈0.8, which are significantly lower than the continental crust values and those of most mantle-derived magmas. Nonmagmatic enrichment in the mantle source is therefore required. Based on published experimental data, two subduction-related metasomatic components, i.e., slab-released hydrous fluid and subducted sediment, are proposed, and the former is considered to be more pervasive for causing the extraordinary trace element ratios observed. Our observations lend support to the notion that dehydration from subducting slabs at convergent margins, as a continuing process through geologic time, can account for the fractionation of these elemental pairs between the Earth's crust and mantle. 相似文献
116.
安徽钱桥-象山角闪石堆晶岩岩石学和地球化学特征 总被引:2,自引:0,他引:2
安微钱桥-象山角闪石堆晶岩是由相当于低硅闪长岩中暗色微粒包体的玄武质岩浆在9.24~12.77km深度和高水压条件下结晶分离作用堆晶形成的。残余的低硅闪长质熔体将它们携带到浅部侵位。结晶分离形成这种堆晶岩的岩浆是玄武质的,可能是由地幔岩中等程度部分熔融形成的拉斑玄武质岩石经再次熔融形成的。 相似文献
117.
118.
亚热带山地土壤的地球化学特征及其与新构造运动的关系 总被引:1,自引:1,他引:1
对亚热带峨眉山、天目山和凤阳山的列样品研究表明,高、低海拔土壤在矿质风化与淋溶、氧化铁富集与转化、粘粒矿物类型及分布等方面均酷为相似,而这些地球化学特性在相同温差水平带的土壤上却有明显区别,由此推算的新构造运动强度与前人研究结构基本一致。这对阐明山地土壤的发生分类及拓宽新构造运动研究方法等有一定参与价值。 相似文献
119.
120.
福建西部震旦系上统变质火山岩属钙碱性系列。REE分布模式均呈向右倾斜的曲线,具Eu负异常,富集大离子系亲石元素和亏损地幔岩相容元素,(86)Sr/(87)Sr初始值0.7105~0.7126,显示陆壳重熔生成的岩浆特点。它们是在浙南-闽西北加里东期挤压碰增造山作用中陆壳重熔岩浆上升喷发产物。 相似文献