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1.
The volcanics exposed in the northeast Niğde area are characterized by pumiceous pyroclastic rocks present as ash flows and fall deposits and by compositions ranging from dacite to rhyolite. Xenoliths found in the volcanics are basaltic andesite, andesite and dacite in composition. These rocks exhibit linear chemical variations between end‐member compositions and a continuity of trace element behaviour exists through the basaltic andesite–andesite–dacite–rhyolite compositional range. This is consistent with the fractionation of ferromagnesian minerals and plagioclase from a basaltic andesite or andesite parent. These rocks are peraluminous and show typical high‐K calc‐alkaline differentiation trends with total iron content decreasing progressively with increasing silica content. Bulk rock and mineral compositional trends and petrographic data suggest that crustal material was added to the magmas by subducted oceanic crust and is a likely contaminant of the source zone of the Niğde magmas. The chemical variations in these volcanics indicate that crystal liquid fractionation has been a dominant process in controlling the chemistry of the northeast Niğde volcanics. It is also clear, from the petrographic and chemical features, that magma mixing with disequilibrium played a significant role in the evolution of the Niğde volcanic rocks. This is shown by normal and reverse zoning in plagioclase and resorption of most of the observed minerals. The xenoliths found in the Niğde volcanics represent the deeper part of the magma reservoir which equilibrated at the higher pressures. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

2.
卫三元 《铀矿地质》1999,15(4):209-216
本文通过对大长沙盆地火山岩岩石学、地球化学特征及同位素的研究,认为盆地盖层火山岩是双旋回式的火山喷溢产物,并且不同旋回的火山岩在岩浆成因、来源深度上是不一样的,是局部熔融的壳幔混合物;第二旋回的中酸性火山岩浆则是上部地壳重熔而形成的  相似文献   

3.
Lead isotopic compositions, and lead and uranium concentrations have been determined for samples from the Tongan islands of Late, Fonualei, Hunga-Ha'apai and Eua and for the Kermadec islands of Raoul, Macauley, Esperance and Napier. The Kermadec samples form a linear array in a Pb206/Pb204 vs Pb207/Pb204 plot which if interpreted in terms of a two stage mantle model indicates a mantle fractionation of Pb from U at about 1.2×109 yr. The Tongan volcanics, except Eua, have a very narrow range of isotopic compositions, only slightly exceeding the experimental error limits. This is interpreted to be the result of efficient mixing of the mantle in response to rapid extension behind the Tongan arc. The rate of extension appears to determine whether convection mixing can occur, since the sub-Kermadec mantle which experienced slower extension is not well mixed isotopically. The isotopic compositions show no evidence for a component in the magma derived from sediments dragged down the Benioff zone. The pre-Eocene Eua volcanics have lead which is substantially more radiogenic than the younger Tongan volcanics and are interpreted as a sample of the mantle before convective mixing occurred.  相似文献   

4.
本文研究了北秦岭及华北地台南缘火山岩约500件岩石化学、120件微量元素和135件稀土元素样品数据。熊耳群、大红口组火山岩属B类的地壳混染型,为大陆裂谷环境;宽坪群、秦岭群变拉斑玄武岩建造属A类的幔源型,为海槽环境;二郎坪群、丹凤群细碧角斑岩建造属C+A、C类的壳幔混合型,为海盆环境。  相似文献   

5.
Summary ?Major and trace element contents and Sr–Nd isotope ratios of selected volcanics of Pliocene age from the Almopia area, central Macedonia, Greece, have been determined. These rocks are mainly distinguished as two groups based on geographical, petrological and isotopic data: a) the east–central western group (E–CW) and b) the south western group (SW). The absence of contemporaneous basic volcanics in the Almopia area coupled with the considerable scatter of elements in variation diagrams rule out fractional crystallization as the dominant differentiation process. Instead, disequilibrium textures along with the positive correlation of Sr-isotope ratios with differentiation suggest mixing between a basic and an acid component combined with assimilation and fractionation. The spider diagrams of the most silica-poor volcanics show evidence of subduction-related processes, indicating that the parental magmas may have been derived from partial melting of mantle wedge enriched in LILE and LREE by subducted slab-derived fluids. Previous data on the oxygen isotope composition of the same volcanics are consistent with this genetic hypothesis. Lastly, the relatively high 87Sr/86Sr and low 143Nd/144Nd ratios (0.7080 and 0.512370, respectively) of the volcanic sample inferred to be compositionally the closest one to the parental magma of Almopia rocks suggest that the incompatible element enrichment of the mantle source is old, probably of Proterozoic age. Received December 12, 2001; revised version accepted June 20, 2002 Published online November 29, 2002  相似文献   

6.
准噶尔盆地西北缘前陆冲断带是剖析西准噶尔地区盆山耦合关系、沉积体系发育的关键地段。该区二叠系佳木河组为火山岩、火山碎屑岩、碎屑岩组成的混积地层。火山岩与碎屑岩组成的地层单元有广义上的成因联系,因为它们都属于史密斯地层,并均具有旋回特征。针对不同的岩性区:碎屑岩岩性区、火山岩与碎屑岩共存区、纯火山岩区,找出由于构造火山活动、相对湖平面变化等因素形成的可作为层序界面的不整合面。碎屑岩岩性区不整合面在地震剖面上主要表现为削蚀、底超、双向下超、顶超、下切谷等;共存区为同时发育火山岩与碎屑岩的削蚀带,不整合面类型较复杂;纯火山岩区表现为相对湖平面下降形成的削蚀不整合面。故可以通过地震、钻测井资料识别各类不整合面,并依据火山喷发方式、火山旋回、沉积旋回,按照不同对比原则进行经典层序地层学划分。  相似文献   

7.
耳闯  王英民  颜耀敏  刘豪  王晓州 《沉积学报》2009,27(6):1101-1108
准噶尔盆地西北缘克—百断裂带是二叠系发育起来的大型叠瓦冲断系统,构造活动对盆地沉积充填过程具有重要的控制作用。二叠系为火山岩和碎屑岩混积地层,分析表明二叠系为层状地层,存在由相对湖平面变化形成的、可作为层序界面的不整合面。根据不整合面和岩层层面对含火山岩系地层进行层序地层的划分和对比,将二叠系划分为5个二级层序,12个三级层序。下二叠统（PSQ1—PSQ7）以火山岩相和沉积岩相共存为特征;中上二叠统（PSQ8—PSQ9）沉积相类型主要包括冲积扇、扇三角洲和湖相。构造活动对层序的控制作用主要表现为构造沉降、火山活动、古地貌特征。构造沉降实质上是逆冲造山导致的挠曲沉降,反映了前陆逆冲作用与盆地挠曲沉降的盆山耦合过程,挠曲沉降是层序形成的内因和主要控制因素;火山作用形成的快速堆积的火山岩体,对含火山岩系地层层序的形成和演化有重要影响;受构造活动影响形成的坡折带控制了层序地层样式和沉积物充填。  相似文献   

8.
Many studies have argued for the contribution of at least three components, namely the mantle wedge, the subducted oceanic crust, and its sediment cover, to describe the geochemistry of island arc volcanics. However, isotope correlations reflecting a simple binary mixing can be observed at the scale of a single arc island or volcano. Here we investigate the possibility that these trends reflect pseudo-binary mixing relationships in a three-component system. We present a simplified, two-stage model for the systematic isotope modelling of a cogenetic suite of arc lavas. This includes metasomatism of portions of the mantle wedge by hydrous phases released from the down-going oceanic crust, and sediments, followed by progressive mixing and melting. A consequence of this model is that it leads to a two end-member mixing process from the mantle wedge, oceanic crust, and sediment components. To solve the model we reduce it to a step-by-step procedure combined with a Monte-Carlo simulation. The procedure consists of: (i) producing a large number of random values on each variable of the model; (ii) using the computed values to calculate the isotopic compositions of lavas; and (iii) comparing the obtained isotopic compositions with measured data. Applied to a new set of Sr, Nd, and Pb isotope data for volcanics (basalts, basaltic andesites, trachybasalts, and basaltic trachyandesites) from Merapi volcano (Java island, Sunda arc), the model successfully reproduces the binary mixing relationships previously documented for the medium-K and high-K lava series from this volcano, thus giving further support to the hypothesis that this distinction is inherited from the primary magmas and primarily reflects a property of the mantle source. The results allow identification of a set of numerical values for bulk partition coefficients (solid/hydrous fluid, and solid/H2O-rich melt) and variables (e.g., the mass ratio between the metasomatizing phase and the mantle wedge), which can be used for quantitative arc-lava petrogenetic calculations. They also require a direct relationship between dehydration of the slab and melting of the metasomatized mantle wedge. Finally, our evaluation shows that for isotope modelling of the Merapi lavas, the two-stage procedure is controlled more by the considered source components (mantle wedge, oceanic crust, sediments, and their derivatives) than by the various processes involved (dehydration, melting, and mixing).  相似文献   

9.
四川呷村V HMS矿床：从野外观察到成矿模型   总被引：22，自引：11，他引：11  
呷村矿床是一个与晚三叠世海相钙碱性酸性火山岩系有关的典型块状硫化物（VHMS）矿床。热水流体系统和贱金属成矿作用发育于义敦岛弧碰撞造山带上的弧间裂谷盆地内,并受其内部的一系列局限盆地及SN向基底断裂－裂缝系统控制。含矿岩系为双峰岩石组合,具火山碎屑岩－矿体－喷气岩“三位一体”特征。硫化物矿床具有“块状矿席＋层控网脉状矿带”式三维结构特征。块状矿席发育多旋回的硫化物－硫酸盐韵律型式,揭示热水流体在海底的幕式排泄以及硫化物－硫酸盐在卤水池内的韵律式化学淀积和滑塌堆积过程。层控网脉状矿带产出于流纹质火山岩系,与上覆的块状矿席平行展布,揭示高渗透性碎屑岩层和多条同级别断层或断裂共同约束海底下部热水流体,并诱导其“弥散式”排泄和侧向流动交代。热水流体的传导冷凝过程导致硫化物沉积、热水流体与冷海水的简单混合导致硅质岩或／重晶石淀积,传导冷凝与海水混合的联合作用导致含硫化物重晶石、硅质岩和红碧玉形成。  相似文献   

10.
This paper addresses the composition, geochemistry, isotopic characteristics, and age of rocks from the Carter Seamount of the Grimaldi seamount group at the eastern margin of the Central Atlantic. The age of the seamount was estimated as 57–58 Ma. Together with other seamounts of the Grimaldi system and the Nadir Seamount, it forms a “hot line” related to the Guinea Fracture Zone, which was formed during the late Paleocene pulse of volcanism. The Carter Seamount is made up of olivine melilitites, ankaramites, and analcime-bearing nepheline tephrites, which are differentiated products of the fractional crystallization of melts similar to an alkaline ultramafic magma. The volcanics contain xenoliths entrained by melt at different depths from the mantle, layer 3 of the oceanic crust, which was formed at 113–115 Ma, and earlier magma chambers. The rocks were altered by low-temperature hydrothermal solutions. The parental melts of the volcanics of the Carter Seamount were derived at very low degrees of mantle melting in the stability field of garnet lherzolite at depths of no less than 105 km. Anomalously high Th, Nb, Ta, and La contents in the volcanics indicate that a metasomatized mantle reservoir contributed to the formation of their primary melts. The Sr, Pb, and Nd isotopic systematics of the rocks show that the composition of the mantle source lies on the mixing line between two mantle components. One of them is a mixture of prevailing HIMU and the depleted mantle, and the other is an enriched EM2-type mantle reservoir. These data suggest that the formation of the Carter Seamount volcanics was caused by extension-related decompression melting in the Guinea Fracture Zone of either (1) hot mantle plume material (HIMU component) affected by carbonate metasomatism or (2) carbonated basic enclaves (eclogites) ubiquitous in the asthenosphere, whose isotopic characteristics corresponded to the HIMU and EM2 components. In the former case, it is assumed that the melt assimilated during ascent the material of the metasomatized subcontinental mantle (EM2 component), which was incorporated into the oceanic lithospheric mantle during rifting and the breakup of Pangea.  相似文献   

11.
Rare earth elements (REE), Ba, Sr as well as major elements in 47 pre-Cenozoic geosynclinal volcanics in Japan have been determined. The types of chondrite-normalized REE patterns can be classified into two large groups viz. log-linear REE pattern group and convex REE pattern group. Each group thus classified is also closely related to major element features. Although the REE pattern of the latter group is observed in the island arc tholeiite as well as abyssal tholeiite, the relative content of Ba to La indicates that the Japanese geosynclinal volcanics of this group are more akin to those of abyssal tholeiites than are the island arc ones. Two distinct types of REE fractionation are found in the volcanics of the Japanese geosyncline. The geographical distribution of two groups of the geosynclinal volcanics is different from that of the Cenozoic volcanics in Japan, and the petrochemical features of volcanics from northeast Japan can be distinguished from those of southwest Japan. By analogy with the current knowledge concerning a close relation between the tectonic settings and the geochemical features of the present-day volcanics, the geosynclinal basalts in question are inferred to have been formed during a tensional tectonic movement and have erupted along a local rift zone like the marginal seas and inter-arc basins in the Western Pacific Ocean or along part of a global rift system such as the Red Sea Trough.  相似文献   

12.
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   

13.
A detailed palaeomagnetic investigation of early Silurian volcanics of the Lawrenceton Formation in the Central Mobile Belt (CMB) of Newfoundland reveals primary remanence that places the sampled part of the CMB on the margin of Laurentia in low southerly latitudes in the early Silurian. The palaeomagnetic data indicate large vertical axis (net clockwise) rotations within the CMB and between the CMB and cratonic Laurentia. The volcanics were folded, faulted and in places cleaved in Silurian to Early Devonian times. Anisotropy of magnetic susceptibility measurements on lava flow samples verify field observations of a primary flow-parallel foliation and confirm field measurements of the palaeo-horizontal. A well-developed tectonic fabric was detected at one sampling site near the Reach Fault.Silurian redbeds of the Big Indian Pond Formation were also sampled for palaeomagnetic study. The sediments are folded, faulted and cleaved. A statistically sound syn-folding remanence was identified which, in a tectonically corrected state, is consistent in direction with the remanence in the Silurian volcanics. The sampled sediments are more intensely deformed than the volcanics and magnetic anisotropy measurements indicate both primary layering- and secondary cleavage-related fabrics in varying degrees from site to site. It is possible that cleavage development resulted in remanence reorientation leading to the illusion of syn-folding remanence when, in fact, the remanence was acquired prior to folding.Previously published palaeomagnetic investigations of Silurian rocks in the CMB revealed a discrepancy in palaeofield inclination between volcanic and sedimentary rock types. The sedimentary rocks yielded shallow inclinations and the volcanics intermediate inclinations. Inclination shallowing in the sediments was put forward as an explanation, as well as contamination of the sedimentary results with a shallow overprint. Others argued that the results from the volcanics were in error. The present investigation demonstrates that key volcanics carry a shallower remanence than previously thought, bringing them into approximate agreement with the majority of the results from sediments. Steep results from the Springdale volcanics and very shallow results from the King George IV lake sediments are at variance with the rest of the data. The Springdale result has large error limits that overlap with the other data. The anomalous King George IV result remains an outlier.  相似文献   

14.
A special kind of magma mixing is extraordinarily well exposed in the Bittersberg subvolcanic complex in the Tertiary volcanic field of the German Westerwald: A trachytic melt has been penetrated by a latitic dyke which has been dispersed within the host magma as small spherical enclaves (globules). Whole rock analyses of the globules show a change in composition that cannot be explained by a simple mechanical mixing between the endmembers. The most evolved globules have a phonolitic composition. Microprobe measurements in the microlithic matrix of the host rock and the guest indicate a diffusive motion of the alkalis from the host into the globules. On the other hand, an opposite trend can be observed for Ca, Mg, Fe and Ti, which are impoverished in the globules. The trace elements and the middle rare earth elements (MREE) has also been involved in the diffusive exchange. The REE-pattern of the most evolved (phonolitic) globules shows a characteristic trough in the area of the MREE which is almost identical to the REE-pattern of many phonolites. The phonolites and the alkali-rich trachytes of the Westerwald show similar globular textures as the Bittersberg volcanics. Therefore, generation of these rocks involving diffusive element exchange during mixing processes in a magma reservoir situated on a deeper crustal level may be possible.  相似文献   

15.
Three magmatic phases are distinguished in the Neoproterozoic Nakora Ring Complex (NRC) of Malani Igneous Suite (MIS), namely (a) Extrusive (b) Intrusive and (c) Dyke phase. Magmatism at NRC initiated with minor amount of (basic) basalt flows and followed by the extensive/voluminous acid (rhyolites-trachytes) flows. The ripple marks are observed at the Dadawari area of NRC in tuffaceous rhyolite flow which suggests the aqueous condition of flows deposition. The emplacement of the magma appears to have been controlled by a well defined NE-SW tectonic lineament and cut by radial pattern of dykes. These NE-SW tectonic lineaments are the linear zones of crustal weakness and high heat flow. The spheroidal and rapakivi structures in the Nakora acid volcanics indicate the relationship between genetic link and magma mixing. Basalt-trachyte-rhyolite association suggests that the large amount of heat is supplied to the crust from the magma chamber before the eruption. The field (elliptical/ring structures), mineralogical and geochemical characteristics of Nakora granites attest an alkaline character in their evolution and consistent with within plate tectonic setting. The emplacement of these granites and associated volcanics is controlled by ring structures, a manifestation of plume activity and cauldron subsidence, an evidence of extensional tectonic environment. NRC granites are the product of partial melting of rocks similar to banded gneiss from Kolar Schist Belt of India. The present investigations suggest that the magmatic suites of NRC rocks are derived from a crustal source and the required heat supplied from a mantle plume.  相似文献   

16.
Volcanic rocks from the southern part of the Tuscan Province, the Tolfa district, range in composition from dacites to rhyolites. They have relatively high contents of many incompatible elements and their 87Sr/86Sr ratios vary between 0.7129 and 0.7148 (28 analyses) with one analysis of 0.7112. The four major eruption centres of the district can be distinguished geochemically. It is shown that the variation of major and trace elements within each area can be explained by fractional crystallization without significant crustal assimilation. The geochemical patterns of the incompatible elements of the investigated volcanics have a close similarity to the alkaline undersaturated volcanics from the nearby Roman Province. The geochemical and isotopic similarity between the Tolfa volcanics and those of the Roman Province suggests a common origin for these components of the magmas. It is suggested that, while the origin of the LIL-element enrichment of the Roman Province magmas is a mantle which was metasomatised by fluids or melts derived from upper crustal material of sedimentary origin recycled into the mantle by subduction, the Tolfa volcanics were derived directly from the subducted material by melting.  相似文献   

17.
黄陵花岗岩基的成因   总被引：18，自引：0，他引：18  
黄陵花岗岩基位于扬子地台北缘，它连同汉南和鲤鱼寨岩基一起构成扬子地台北缘的低钾花岗岩等，形成于晋宁晚期扬子地台北侧的“秦岭洋”壳向南俯冲导致的大陆边缘造山运动过程中。黄陵花岗岩基可解体为三斗坪、黄陵庙、大老岭、晓峰4个岩套和14个单元，侵位于832－750Ma之间。三斗坪和黄陵庙两个岩套主要由英云闪长岩、奥长花岗岩花岗闪地组成，是在近南北向区域挤压下于约16km深部塑性域定位的同构造花岗岩，前者主要依靠岩浆在构造弱面逐次强力楔入创造定位空间，后者主要在处于活动状态的韧性拉张剪切带内定位。钙碱性系列的大老岭和晓峰岩套则是在本区地壳迅速隆起过程中分别在5km和＜1．5km深度的脆性域定位的构造晚期花岗岩。根据岩石化学和同位素组成推断，三斗坪岩套的源岩主要是晚太古代大陆拉斑玄武岩，母岩浆相当于英安质，岩套内的成分变化主要受角闪石分离结晶作用控制；黄陵庙岩套除受分离结晶作用影响外，成分变化主要与英安质母岩浆和某种长英质岩浆的混合有关；大老岭岩套的源岩亦为早前寒武纪火山岩。  相似文献   

18.
Extensive Permo-Carboniferous volcanism has been documented from the Bohemian Massif. The late Carboniferous volcanic episode started at the Duckmantian–Bolsovian boundary and continued intermittently until Westphalian D to Stephanian B producing mainly felsic and more rarely mafic volcanics in the Central Bohemian and the Sudetic basins. During the early Permian volcanic episode, after the intra-Stephanian hiatus, additional large volumes of felsic and mafic volcanics were extruded in the Sudetic basins. The volcanics of both episodes range from entirely subalkaline (calc-alkaline to tholeiitic) of convergent plate margin-like type to transitional and alkaline of within-plate character. A possible common magma could not be identified among the Carboniferous and Permian primitive magmas, but a common geochemical signature (enrichment in Th, U, REE and depletion in Nb, Sr, P, Ti) in the volcanic series of both episodes was recognized. On the other hand, volcanics of both episodes differ in intensities of Nb, Sr and P depletion and also, in part, in their isotope signatures. High 87Sr/86Sr (0.707–0.710) and low εNd (−6.0 to −6.1) are characteristic of the Carboniferous mafic volcanics, whereas low 87Sr/86Sr (0.705–0.708) and higher εNd ranging from −2.7 to −3.4 are typical of the Permian volcanics. Felsic volcanics of both episodes vary substantially in 87Sr/86Sr (0.705–0.762) and εNd (−0.9 to −5.1). Different depths of magma source or heterogeneity of the Carboniferous and Permian mantle can be inferred from variation in some characteristic elements of the geochemical signature for volcanics in some basins. The Sr–Nd isotopic data with negative εNd values confirm a significant crustal component in the volcanic rocks that may have been inherited from the upper mantle source and/or from assimilation of older crust during magmatic underplating and ascending of primary basic magma. Two different types of primary magma development and formation of a bimodal volcanic series have been recognized: (i) creation of a unique magma by assimilation fractional crystallization processes within shallow-level reservoirs (type Intra-Sudetic Basin) and (ii) generation and mixing of independent mafic and felsic magmas, the latter by partial melting of upper crustal material in a high-level chamber (type Krkonoše Piedmont Basin). A similar origin for the Permo-Carboniferous volcanics of the Bohemian Massif is obvious, however, their geochemical peculiarities in individual basins indicate evolution in separate crustal magma chambers.  相似文献   

19.
华北克拉通南缘早白垩世中基性火山岩成因及其地质意义   总被引：8，自引：5，他引：3  
平顶山早白垩世大营组中基性火山岩样品为钾质和钾玄岩石系列,主要由粗安岩组成,属于偏铝质岩石。低MgO(2.25%~2.88%)和Cr(17.5~30.0μg/g)、Ni(17.4~23.3μg/g),高Al2O3(17.32%~17.56%)和K2O(4.43%~4.56%),K2O/Na2O>1。稀土表现出LREE富集的右倾平滑分布型式,(La/Yb)CN=14.0~14.7,HREE弱分馏,(Gd/Yb)CN=2.42~2.66,富集Rb、Ba、K、LREE和亏损Nb-Ta、Th,弱的Sr正异常。Sr-Nd同位素较富集87Sr/86Sr(t)=0.706877~0.707005,εNd(t)=-10.9~-11.6。大营组中基性火山源区岩的稀土、微量元素地球化学和同位素组成类似于晚中生代苏鲁造山带基性火山岩,北大别镁铁-超镁铁质侵入体和北淮阳中基性火山岩(Fanetal.,2001,2004;Wangetal.,2005),暗示其可能具有相似的岩石成因,即大营组中基性火山来自于古老陆下岩石圈地幔和深俯冲的扬子下地壳混合源区的部分熔融作用,说明华北和扬子陆块在三叠纪碰撞过程中,扬子陆壳深俯冲再循环进入华北岩石圈地幔,其形成与板块俯冲作用没有直接的动力学关系,而形成于陆内伸展拉张环境下。  相似文献   

20.
纸房地区早奥陶世海相火山岩岩石化学特征   总被引：2，自引：0，他引：2  
纸房地区具有早奥陶世海相火山岩存在。火山岩层中以溢流相的中基性火山岩为主 ,局部地段比较发育以酸性岩类为主的次火山岩 ,中基性火山岩的岩石化学类型属于拉斑玄武岩钠质类型。岩石化学特征表明火山岩形成于洋岛构造环境  相似文献   

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