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1.
The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in Iherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometry. These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in Iherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H2, CO2 and CO, and are characterized by high contents of H2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO2 and H2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H2, while CO2 a  相似文献   

2.
Cenozoic（Miocene to Pleistocene） basaltic rocks in Jiangsu province of eastern China include olivine tholeiite and alkali basalt.We present major,trace element and Sr-Nd isotopic data as well as Ar-Ar dating of these basalts to discuss the petrogenesis of the basalts and identify the geological processes beneath the study area.On the basis of chemical compisitions and Ar-Ar dating of Cenonoic basaltic rocks from Jiangsu province,we suggest that these basalts may belong to the same magmatic system.The alkali basalts found in Jiangsu province have higherΣFeO,MgO,CaO,Na2O, TiO2 and P2O5 and incompatible elements,but lower Al2O3 and compatible elements contents than olivine tholeiite which may be caused by fractional crystallization of olivine,pyroxene and minor plagioclase.In Jiangsu basaltic rocks the incompatible elements increase with decreasing MgO/ΣFeO ratios.The primitive mantle-normalized incompatible elements and chondrite-normalized REE patterns of basaltic rocks found in Jiangsu province are similar to those of OIB.Partial loss of the mantle lithosphere accompanied by rising of asthenospheric mantle may accelerate the generation of the basaltic magma.The 143Nd/144Nd vs.87Sr/86Sr plot indicates a mixing of a depleted asthenospheric mantle source and an EMI component in the study area.According to Shaw’s equation,the basalts from Jiangsu province may be formed by l%-5%partial melting of a depleted asthenospheric mantle source.On the basis of Ar-Ar ages of this study and the fractional crystallization model proposed by Brooks and Nielsen（1982）,we suggest that basalts from Jiangsu province may belong to a magmatic system with JF-2 as the primitive magma which has undergone fractional crystallization and evolved progressively to produce other types of basalts.  相似文献   

3.
Cretaceous volcanism in the coastal region of southeastern China was characteristized by occurrenceof bimodal volcanics consisting of basalts and rhyolites, the geneses of which are still controversial. Based on the factthat their isotopic compositions are similar but the Sr content of the former is much higher than that of the latter, thispaper discusses the respective sources of the two end-member rocks, and concludes that basalts were derived fromthe subduction-related enriched upper mantle wedge and their isotopic compositions had not been affected by crustalassimilation, whereas rhyolites were formed by remelting of the old metamorphic basement, but they were mixed upwith the underplating basaltic magmas to various degrees so that their Sr isotopic compositions varied significantlyfrom the sources and tended to be homogeneous to the latter.  相似文献   

4.
Cenozoic lavas from Hainan Island,South China,comprise quartz tholeiite,olivine tholeiite,alkali basalt,and basanite and form a continuous,tholeiite-dominated,compositional spectrum.Highly incompatible elements and their relationships with isotopes in these lavas are shown to be useful in evaluating mantle-source composition,whereas modeling suggests that ratios of elements with bulk partition coefficients significantly larger than those of Nb and Ta may be sensitive to partial melting.Th/Ta and La/Nb ratios of alkali basalts are lower than those of tholeiites,and they are all lower than those of the primitive mantle,These ratios correlate positively with ^207Pb/^204Pb and ^87Sr/^86Sr ratios.Such relationships can be explained by mixing of depleted and enriched source components.A depleted component is indicated by alkali basalt compositions and is similar to some depleted OIB (PREMA).The enriched component,similar to sediment compositions,is indicated by tholeiites with high LILE/HFSE,^207Pb/^204Pb,and ^87Sr/^86Sr ratios.In general,basalts from Hainan and the South China Basin(SCB)share common geochemical characters.e.g.high Rb/Sr,Th/Ta,^207Pb/^206Pb,and low Ba/Th ratios.Such a geochemical trend is comparable to that of EMII-type OIB and best explained as the result of subduction.Occurrence of these characteristics in both continental Hainan basalts and SCB seamout basalts indicates the presence of a South China geochemical domain that exists in the mantle region below the lithosphere.  相似文献   

5.
于学元 《地球化学》1984,(3):247-255
The Nutoushan basaltic cone, eonsisting of subalkali (quartz-tholeiite and olivinetholeiite) and alkali basalts, is Late Tertiary in age. Its major characteristics are generalized as follows: (1) Both early subalkali and late alkali basalts are formed under the same geological environment. (2) The continuity in chemical composition from snbalkali to alkali and the low FeO/MgO in alkali basalts show that they arc the products of cognate magmatic diffcrcntiation. (3) The change from low REE abundance and weak enrichment of LREE in subalkali to high REE abundance and strong enrichment of LREE in alkali basalts indicates obvious REE cnrichment and fractionation during magmatic differentiation.Weak positive Eu anomalies in the REE patterns arc indicative of their formation under low oxygen fugacity conditions. (4) According to the calculated values, 70-75% of the primary olivine tholeiitic magma had been separated as subalkaline basalic magma, the rest residual magma became alkaline basaltic magma. This result is consistent to the field observation that the outcrop area of subalkali basalts is four times as much as that of alkali basalts. (5) The basaltic rocks of Nutoushan show an S-type distribution straddling the thermal barrier on Ol‘-Ne‘-Qu‘ diagram and an evolution tendency for Ne to increase with increasing FeO/MgO. This is in agreement with the melting experimental data on olivine basalts at 10-20 kb. (6) Mantle-derived inclusions (spinel lherzolite) in this area occur in both alkali olivine basalts and olivine tholeiites. The latter is of extremely rare oceurrence. The formation temperature and pressure of the inclusions in alkali basalts and olivine tholeiites have been calculated. The results silow that the alkaline basaltic magma was separated from the subalkaline basaltic magma at about 20 kb. Basaltic rocks in Nutoushan were formed through the soealled “high pressure differentiation”, that is, at about 20 kb the crystallization of clinopyroxene and orthpyroxene resulted in the separation of subalkaline basaltic magma from the primary olivine tholeiitic magma, and then the residue gradually became alkaline olivine basaltic magma.  相似文献   

6.
The colours and chemical composition variations of 160 spinels in peridotite and pyroxenite xenoliths from Cenozoic basalts in eastern China and their petrogeneses have been studied in detail. The relationships between major elements of spinels are discussed. The equilibrium temperatures, pressures and oxygen fugacities of spinels and their coexisting olivines, orthopyroxenes and clinopyroxenes have been determined using the Brey-kohler' s T-P calculation methods (1990) and Ballhaus' fo2 calculation method (1991). The relationships betweenthe composition and the equilibrium temperatures, pressures or oxygen fugacities of spinels in peridotite xenoliths from the basalts and the stable field of the spinels in the upper mantle have been shown.  相似文献   

7.
The method of determining the nitrogen isotopic composition of granites in the northeastern part of China is described.The content and isotopic values of nitrogen released from granite samples by stepwise heating were determined as well.The results showed that the diferent areas of northeastern China hae a great difference in nitrogen content and isotopic composition.Nitrogen released from the granites is 1.64-6.23μL/g ,with the maximum at about 600℃,from rhyolite and granophyre is 108.98-755.96μL/g,with the maximum at about 900℃,It is proved that fluid is characterized by heterogeneity in the deep crust of the different areas in northeastern China.The nitrogen isotopic compositions in different ranges of temperautes are wweighted.And the nitrogen isotopic compositions in different anges of temperatures are weighted.And the nitrogen isotopic values are 9.2‰ to 17.0‰,with a variation range of 7.8‰,The nitrogen isotopic ratios may have been fractionated during degassing and the fluid released from granites is the residual component.  相似文献   

8.
南海玄武岩的某些地球化学特征   总被引：14，自引：1，他引：14  
Petrochemistry,geochronology,trace and REE geochemistry have been studied of a few basalts from the South China Sea.The results show that the South China Sen basalts may be divided into two types;alkali basalts and tholeiites.The former is similar to common alkali basalts in petrochemistry,REE distribution pattern and trace element geochemistry,but the latter is similar to Hawaiian tholeiites,belonging to the transition type between alkali basalt and MORB(mid-oceanic rise basalt).  相似文献   

9.
Reported in this paper are the chemical compositions and trace element (REE,Ba,Rb,Sr,Nb,Zr,Ni,Cr,V,Ga,Y,Sc,Zn,Cu,etc)abundances of Tertiary continental alkali basalts from the Liube-yizheng area,Jiangsu Province,China.The olivine basalt,alkali olivine basalt and basanite are all derived from evolved melts which were once af-fected by different degrees of fractional crystallization of olivine and clinopyroxene(1:2)under high pres-sures.The initial melts were derived from the garnet lherzolite-type mantle source through low-degree par-tial melting.The mantle source has been affected by recent mantle-enrichment events(e.g.mantle metasomatism),resulting in incompatible trace element enrichment and long-term depletion of radiogenic isotopic compositions of Sr and Nd.  相似文献   

10.
The lead isotopic compositions of feldspars and ores from granitoid rocks andassociated hydrothermal ore deposits in eastern China are strictly controlled by the nature and age of basement rocks in different tectonic belts.In eastern China,at least five discrete plumbotectonic provinces can be distinguished:the North China platform province,the Qinling province,the Lower Yangtze prov-ince,the Nanling province and the Southeast China coastal province.Each province is marked for unique types of mineralization and ore-metal assemblages.  相似文献   

11.
张铭杰  王先彬 《地球化学》1998,27(5):452-457
利用热分解质谱法测定了中国东部新生代碱性玄武岩中流体挥发分的组成,并对不同温度段释放出的ＣＯ２气体测定了Ｃ,Ｏ同位素值,流体组成和ＣＯ２的Ｃ,Ｏ同位素值表明中国东部上地幔源区的不均一性,与其中所含幔源岩捕体相比,碱性玄武岩浆发育在相对氧化的环境中,并有外来流体组分的加入。  相似文献   

12.
Cenozoic basaltic volcanism in southeastern China was related to the lithospheric extension and asthenospheric upwelling at the eastern Eurasian continental margin. The cenozoic basaltic rocks from this region can be grouped into three different series: tholeiitic basalts, alkali basalts, and picritic-nephelinitic basalts. Each basalt series has distinctive geochemical features and is not derived from a common source rock by different degrees of partial melting or from a common parental magma by fractional crystallization. The mineralogy, petrography, and major and trace-element geochemistry of the tholeiites are similar to oceanic island basalts, implying that the mantle source for these Chinese continental tholeiites was similar to that of the oceanic island basalts—an asthenospheric mantle. The alkali basalts and picritic-nephelinitic basalts are enriched in incompatible trace elements, and their geochemical features can be interpreted as a result of partial melting of an enriched lithospheric mantle, or the mixing products of an asthenospheric magma with a component derived from an enriched lithospheric mantle through thermal erosion at the base of the lithosphere. But the lack of a transitional rock type and continuous variational trends among these basalts suggests that the mixing between asthenospheric magmas and lithospheric magmas probably was not significant in the petrogenesis of the basalts from SE China. Low-degree partial melting of enriched lithospheric mantle alone can account for the observed geochemical data from these basalts.  相似文献   

13.
花岗岩结晶分离作用问题——关于花岗岩研究的思考之二   总被引：11，自引：15，他引：11  
岩浆结晶分离作用是一个古老的话题,很早就有学者指出,地球内部生成的岩浆大多是玄武质岩浆,大多数花岗岩是由玄武岩结晶分离形成的。本文在考察了岩浆结晶分离作用的制约因素、比较了不同性质岩浆结晶分离作用的特征之后指出:玄武质岩浆可以发生结晶分离作用,因为有与其相关的堆晶岩产出;安山质岩浆也可以发生结晶分离作用,因为也有与其相关的堆晶岩产出。但是,花岗质岩浆似乎不大可能发生结晶分离作用,因为,很少见到有与(富硅的)花岗质岩浆相伴的堆晶岩产出。花岗质岩浆之所以不大可能发生结晶分离作用的原因在于:(1)岩浆的黏性大,它不仅阻滞了矿物的结晶作用(使斜长石不能发育为自形晶),而且阻止了密度大的矿物(例如角闪石)下沉;(2)主要造岩矿物(例如斜长石)的密度与花岗质岩浆的密度相差无几,使结晶分离作用难以进行。本文详细考察了花岗质岩浆中斜长石的行为,指出在花岗质岩浆中斜长石结晶分离几乎是不可能的。那么,文献中大量充斥的花岗岩结晶分离作用的说法是依据什么呢?作者认为,文献中的许多说法可能主要是根据哈克图解得出的,而不是根据实际观察和理论研究得出的。作者认为,玄武岩和花岗岩不仅来源不同,成分不同,而且解释也不同。哈克图解中许多适合玄武岩的解释未必适合花岗岩。由于鲍文反应原理是结晶分离作用的理论基础,因此,文中也对鲍文反应原理进行了评述,并指出文献中存在的一些需要认真对待的问题,例如,从玄武岩-安山岩-英安岩-流纹岩的连续演化序列是不可能的;单元-超单元填图方法是不科学的;中国东部中生代大规模花岗岩不可能是玄武质岩浆结晶分离形成的等等。本文还以 Ajaji el ai.(1998)报道的摩洛哥 Tanncherfi 花岗岩为例,指出结晶分离作用的解释是不可能的。作者认为,花岗岩类的成分变化大,主要可能与源区组成、温度、压力、挥发分、部分熔融程度和过程、混合作用、岩浆分异及结晶分离作用有关。其中,源区组成可能是花岗岩多样性的最重要的原因,而结晶分离作用的影响可能是微乎其微的。本文认为,花岗岩结晶分离作用对于花岗岩成因的意义已经被大大地夸大了,我们应当重新思考结晶分离作用对于花岗质岩浆的意义。由于花岗岩的极端复杂性,许多问题还得不到比较合理的解释,本文的认识只是初步的。  相似文献   

14.
Epuptions of alkali and subalkali basalts occurred respectively during Paleogene, Neogene, and Quaternary in North China. They are interplate, non-oceanic basalts. The alkali basalts range from Ne-normative to Hy-normative basalts and the subalkali basalts belong to the continental tholeiites. Based on their distribution, geological ages and petrographic series the magmatic evolution of Cenozoic basaltic rocks in North China can be divided into three stages. Geochemical data from this study indicate that Cenozoic basaltic magmas of North China were derived from two different mantle sources.  相似文献   

15.
本文对华北克拉通晚中生代和新生代碱性玄武质岩石中的单斜辉石巨晶进行了主、微量元素和Sr-Nd同位素的综合研究,发现晚中生代和新生代单斜辉石巨晶存在明显的主、微量元素和同位素组成上的差异。新生代单斜辉石巨晶有Al-普通辉石和次透辉石两类;而中生代单斜辉石巨晶只有Al-普通辉石。新生代单斜辉石SiO_2含量高、REE配分型式为上凸型、LILE和放射性元素含量高,并具有比寄主碱性玄武岩更亏损的Sr和Nd同位素组成;而中生代单斜辉石SiO_2含量低、REE配分型式为LREE富集型、LILE和部分HFSE以及放射性元素含量低,并具有比寄主碱性玄武岩稍富集的Sr和Nd同位素组成;巨晶的结构、矿物成分和地球化学特征,以及Mg-Fe在熔体与单斜辉石间的分配状况皆说明,新生代碱性玄武岩中单斜辉石巨晶是碱性玄武岩浆在高压下结晶的,因此二者是同源的;而中生代单斜辉石巨晶是被寄主岩浆偶然捕获的捕虏晶,是不同源的。华北新生代单斜辉石巨晶存在于碱性玄武岩和拉斑玄武岩中,它们具有比寄主碱性玄武岩更亏损的Sr和Nd同位素组成,说明即使是碱性玄武岩也不能完全代表软流圈来源的原始岩浆,其在上升过程中或多或少存在同位素组成富集的物质的混入。同时,拉斑玄武岩不是碱性玄武质岩浆直接结晶分异的产物,亦不是完全由部分熔融程度的不同造成的。拉斑玄武岩中存在岩石圈地幔物质的贡献或是岩浆房内碱性玄武质岩浆受地壳混染作用的结果。  相似文献   

16.
To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0–55.5 wt.% SiO2), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by ~13% melting of a source mantle with ~0.7 wt.% H2O at 1245–1260?°C and ~1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937–1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to ~AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from ~AD 1960 to present.  相似文献   

17.
Volcanic rocks of the Latir volcanic field evolved in an open system by crystal fractionation, magma mixing, and crustal assimilation. Early high-SiO2 rhyolites (28.5 Ma) fractionated from intermediate compositionmagmas that did not reach the surface. Most precaldera lavas have intermediate-compositions, from olivine basaltic-andesite (53% SiO2) to quartz latite (67% SiO2). The precaldera intermediate-composition lavas have anomalously high Ni and MgO contents and reversely zoned hornblende and augite phenocrysts, indicating mixing between primitive basalts and fractionated magmas. Isotopic data indicate that all of the intermediate-composition rocks studied contain large crustal components, although xenocrysts are found only in one unit. Inception of alkaline magmatism (alkalic dacite to high-SiO2 peralkaline rhyolite) correlates with, initiation of regional extension approximately 26 Ma ago. The Questa caldera formed 26.5 Ma ago upon eruption of the >500 km3 high-SiO2 peralkaline Amalia Tuff. Phenocryst compositions preserved in the cogenetic peralkaline granite suggest that the Amalia Tuff magma initially formed from a trace element-enriched, high-alkali metaluminous magma; isotopic data suggest that the parental magmas contain a large crustal component. Degassing of water- and halogen-rich alkali basalts may have provided sufficient volatile transport of alkalis and other elements into the overlying silicic magma chamber to drive the Amalia Tuff magma to peralkaline compositions. Trace element variations within the Amalia Tuff itself may be explained solely by 75% crystal fractionation of the observed phenocrysts. Crystal settling, however, is inconsistent with mineralogical variations in the tuff, and crystallization is thought to have occurred at a level below that tapped by the eruption. Spatially associated Miocene (15-11 Ma) lavas did not assimilate large amounts of crust or mix with primitive basaltic magmas. Both mixing and crustal assimilation processes appear to require development of relatively large magma chambers in the crust that are sustained by large basalt fluxes from the mantle. The lack of extensive crustal contamination and mixing in the Miocene lavas may be related to a decreased basalt flux or initiation of blockfaulting that prevented pooling of basaltic magma in the crust.  相似文献   

18.
The Okete Volcanics form small volume monogenetic volcanoes situated around the flanks of larger tholeiitic cones of the Plio-Pleistocene Alexandra Volcanics, in the back-arc tectonic environment of western North Island, New Zealand. The lavas and tuffs of the Okete Volcanics have compositions which include basanites, alkali olivine basalts, olivine tholeiites, and hawaiites. Most rocks have Mg numbers >66, >250 p.p.m. Ni, >500 p.p.m. Cr, and often contain ultramafic xenoliths, which indicate that they are very close to being primary magmas. The Okete Volcanics show geochemical trends, from basanite to hawaiite, of progressive depletion of both compatible and incompatible trace elements, progressive increase in Al2O3, and heavy REE and Y enrichment with crossingover REE patterns in the hawaiites. These geochemical trends can be accounted for by varying degrees of partial melting of a light REE enriched garnet peridotite with subsequent modification of the melts near source or during ascent by fractional crystallization of olivine and minor clinopyroxene. Mass balance calculations cannot quantitatively constrain the degree of partial melting or fractional crystallization, but nevertheless indicate that the Okete alkali olivine basalts, olivine tholeiites, and hawaiites have been derived by successively larger degrees of partial melting relative to basanites, and have also been progressively more modified by fractional crystallization than have the basanites. Sources of the alkalic melts lay at depths corresponding to >20 kb, and most of the ultramafic xenoliths, apart from some which may be cognate cumulates, are unrelated to the magmas that brought them to the surface. Magmas have changed in composition with time from older smaller-volume volcanoes of basanite or alkali olivine basalt compositions, to younger and more voluminous volcanoes which contain hawaiites. The geochemical trends shown by the Okete Volcanics and their spatial association with voluminous tholeiitic volcanism, are features which are different from those observed elsewhere in the Pliocene to Recent basaltic fields of northern North Island, and may be related to their unique tectonic setting, situated in a distinct structural domain.  相似文献   

19.
Thirty-one plugs of alkaline volcanic rocks of Cenozoic age (37 Ma in mean) occur in the Upper Benue valley, northern Cameroon (Central Africa). The complete alkaline series (alkaline basalts, hawaiites, mugearites, phonolites, trachytes and rhyolites) is represented. Basalts contain phenocrysts of olivine, Al-Ti-rich diopside, and Ti-magnetite, and hawaiites-abundant microphenocrysts of plagioclase. Mugearites have a trachytic texture and contain xenocrysts of K-feldspar, apatite, quartz and unstable biotite. Phonolites are peralkaline. Trachytes (peralkaline and non-peralkaline) and rhyolites are characterised by their sodic mineralogy with aegirine-augite, richterite, and arfvedsonite phenocrysts. There is a large compositional gap between basaltic and felsic lavas, except the mugearites. Despite this gap, major- and trace-element distributions are in favour of a co-magmatic origin for the basaltic and felsic lavas. The Upper Benue valley basalts are similar in their chemical and isotopic features to other basalts from both the continental and oceanic sectors of the Cameroon Line. The Upper Benue valley basaltic magmas (87Sr/86SrƸ.7035; k Nd=+3.9) originate from an infra-lithospheric reservoir. The Sr-Nd isotopic composition and high Sr contents of the mugearites suggest that they are related to mantle-derived magmas and that they result from the mixing, at shallow crustal levels, of a large fraction of trachytic magma with a minor amount of basaltic magma. Major-element modelling of the basalt-trachyte evolution (through hawaiite and mugearite compositions) does not support an evolution through fractional crystallization alone. The fluids have played a significant role in the felsic lavas genesis, as attested by the occurrence of F-rich minerals, calcite and analcite. An origin of the Upper Benue valley rhyolitic magmas by fractional crystallization of mantle-derived primitive magmas of basaltic composition, promoted or accompanied by volatile, halogen-rich fluid phases, may be the best hypothesis for the genesis of these lavas. These fluids also interact with the continental crust, resulting in the high Sr-isotope initial ratios (0.710) in the rhyolites, whereas the Nd isotopic composition has been less affected (k Nd=+0.4).  相似文献   

20.
Cenozoic basalts widespread in eastern China constitute an important sector of the circum-Pacific Cenozoic basalt belt. Basalt samples were collected from Wudalianchi (Heilongjiang Province), Nushan (Anhui Province), Fangshan (Jiangsu Province), Zhuji (Zhejiang Province), and Mingxi(Fujian Province). These basalts, for the most part, belong to the alkali basaltic series, and partly to tholeiites. A variety of inclusions commonly occurs in the rock-forming minerals of these basalts. The physicochemical conditions of basalt formation in different areas have been reviewed in special reference to the inclusion data. Our studies have shown that there is a close relationship between the features of the inclusions and the physicochemical conditions of basalt formation, which can, therefore, be regarded as a guide to the mechanism of basaltic petrogenesis. The results of research in this aspect are presented in the present paper.  相似文献   

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