Geochemistry of subalkaline and alkaline extrusives from the Kermanshah ophiolite,Zagros Suture Zone,Western Iran: implications for Tethyan plate tectonics

The Kermanshah ophiolite is a highly dismembered ophiolite complex that is located in western Iran and belongs to the Zagros orogenic system. The igneous rocks of this complex consist of both mantle and crustal suites and include peridotites (dunite and harzburgite), cumulate gabbros, diorites, and a volcanic sequence that exhibits a wide range in composition from subalkaline basalts to alkaline basalts to trachytes. The associated sedimentary rocks include a variety of Upper Triassic to Lower Cretaceous deep- and shallow-water sedimentary rocks (e.g., dolomite, limestone, and pelagic sediments, including umber). Also present are extensive units of radiolarian chert. The geochemical data clearly identifies some of the volcanic rocks to have formed from two distinct types of basaltic melts: (i) those of the subalkaline suite, which formed from an initial melt with a light rare earth elements (LREE) enriched signature and incompatible trace element patterns that suggest an island arc affinity; and (ii) those of the alkaline suite with LREE-enriched signature and incompatible trace element patterns that are virtually identical to typical oceanic island basalt (OIB) pattern. The data also suggests that the trachytes were derived from the alkaline source, with fractionation controlled by extensive removal of plagioclase and to a lesser extent clinopyroxene. The presence of compositionally diverse volcanics together with the occurrence of a variety of Triassic–Cretaceous sedimentary rocks and radiolarian chert indicate that the studied volcanic rocks from the Kermanshah ophiolite represent off-axis volcanic units that were formed in intraplate oceanic island and island arc environments in an oceanic basin. They were located on the eastern and northern flanks of one of the spreading centers of a ridge-transform fault system that connected Troodos to Oman prior to its subduction under the Eurasian plate.     

Early Cenozoic volcanism of the Kolyuchin-Mechigmen graben, Chukotka Peninsula

The paper reports new isotope-geochemical data on Late Paleocene-Early Eocene basalts from the central part of the Kolyuchin-Mechigmen graben, eastern Chukotka Peninsula. The distribution of the major and trace elements and trace-element ratios indicates that the basalts were formed in a marginal-continental rift setting. The peculiar feature of the basalts is a combination of depleted within-plate and suprasubduction geochemical signatures, which make the volcanic rocks from Mt. Otdel’naya different from rocks of suprasubduction volcanic belts and from tholeiites and alkaline lavas of continental rifts and oceanic islands. Extremely high ⁸⁷Sr/⁸⁶Sr ratios in the studied basalts as compared to those of similar volcanic rocks from extension zones are probably related to the involvement of carbonate material in the magma generation zone.     

Basalts of the Pantalassa ocean in the Samarka terrane, Central Sikhote Alin

Basalts developed on the right bank of the Matai River belong to the Samarka terrane (Central Sikhote Alin), which is a fragment of the Jurassic accretionary prism. They associate with Carboniferous-Permian reef limestones, Permian pelagic cherts, Jurassic hemipelagic cherty-clayey deposits, and terrigenous rocks of the near-continental sedimentation area. The petrogeochemical features of the basalts provide insight into the character of the volcanism in different settings of the ancient Pantalassa ocean. In terms of chemistry, the Carboniferous-Permian basalts are similar to the within-plate ocean-island basalts related to plume mantle sources. They were presumably formed in an oceanic area with numerous islands and seamounts. The Permian basalts associated with cherts are tholeiitic in composition and were formed from depleted mantle in a spreading center located in the pelagic area. The Jurassic basalts are of plume origin and, in terms of geochemistry, occupy an intermediate position between OIB and E-MORB. They were presumably formed in a convergent zone in a geodynamic setting of rapid oblique subduction.     

Geochemical discrimination of metabasalt rocks of the Fan–Karategin transitional blueschist/greenschist belt, South Tianshan, Tajikistan: seamount volcanism and accretionary tectonics

The Fan–Karategin metamorphic belt, South Tianshan, Tajikistan, is regarded to be an ancient subduction–accretionary complex and is composed of three tectonostratigraphic units which display lithologies consistent with different tectonic settings. The mafic schists, which make up the major part of the older unit of the belt, contain both alkali and tholeiitic metabasalts. On the basis of rare-earth and other immobile element characteristics, the alkali metabasalts are akin to within-plate ocean island basalts, whereas the tholeiitic metabasalts resemble E-type MORB. The association is interpreted to have been formed on seamount-like structures under a within-plate plume. Bedded cherts and marbles in the unit are regarded as ancient pelagic sediments and carbonate caps developed upon basaltic seamounts, respectively. Dismemberment of the seamount-related basalts and pelagic sediments and the high-P/low-T prograde metamorphism of the unit rocks up to transitional blueschist/greenschist facies was the result of paleoseamount submergence into a subduction zone. This unit is tectonically overlain by arc-derived metavolcanic unit and a disrupted, mainly clastic unit of Upper Ordovician–Lower Silurian age. Metavolcanic and metasedimentary rocks of the two upper units have geochemical characteristics compatible with subduction-related origin. The lithological assemblages of the individual units and their juxtaposition suggest an origin involving collision–accretionary processes. The Fan–Karategin belt is a subduction–accretionary complex which formed during subduction of oceanic crust under a volcanic arc and was subjected to tectonic juxtaposition and imbrication of seamount, deep-sea, trench and volcanic arc sequences.     

Composition, sources, and mechanism of continental crust growth in the Lake zone of the Central Asian Caledonides: I. Geological and geochronological data

Data on the composition, inner structure, and age of volcanic and siliceous-terrigenous complexes and granitoids occurring in association with them in the Caledonian Lake zone in Central Asia are discussed in the context of major relations and trends in the growth of the Caledonian continental crust in the Central Asian Foldbelt (CAFB). The folded structures of the Lake zone host basalt, basalt-andesite, and andesite complexes of volcanic rocks that were formed in distinct geodynamic environments. The volcanic rocks of the basalt complex are noted for high concentrations of TiO₂ and alkalis, occur in association with fine-grained siliceous siltstone and siliceous-carbonate rocks, are thus close to oceanic-island complexes, and were likely formed in relation to a mantle hotspot activity far away from erosion regions supplying terrigenous material. The rocks of the basalt-andesite and andesite complexes have lower TiO₂ concentrations and moderate concentrations of alkalis and contain rock-forming amphibole. These rocks are accompanied by rudaceous terrigenous sediments, which suggests their origin in island-arc environments, including arcs with a significantly dissected topography. These complexes are accompanied by siliceous-terrigenous sedimentary sequences whose inner structure is close to those of sediments in accretionary wedges. The folded Caledonides of the Lake zone passed through the following evolutionary phases. The island arcs started to develop at 570 Ma, their evolution was associated with the emplacement of layered gabbroids and tonalitetrondhjemite massifs, and continued until the onset of accretion at 515–480 Ma. The accretion was accompanied by the emplacement of large massifs of the tonalite-granodiorite-plagiogranite series. The postaccretionary evolutionary phase at 470–440 Ma of the Caledonides was marked by intrusive subalkaline and alkaline magmatism. The Caledonides are characterized by within-plate magmatic activity throughout their whole evolutionary history, a fact explained by the accretion of Vendian-Cambrian oceanic structures (island arcs, oceanic islands, and back-arc basins) above a mantle hotspot. Indicators of within-plate magmatic activity are subalkaline high-Ti basalts, alkaline-ultrabasic complexes with carbonatites and massifs of subalkaline and alkaline gabbroids, nepheline syenites, alkaline granites, subalkaline granites, and granosyenites. The mantle hotspot likely continued to affect the character of the lithospheric magmatism even after the Caledonian folded terrane was formed.     

Geochemical Characteristics of Volcanic Rocks of the Laochang Ag Polymetallic Deposit,Lancang,Yunnan Province,China

In terms of major element, trace element and REE geochemical characteristics ofvolcanic rocks in the area studied and by making use of the TiO2-K2O-P2O5,The-Hf-Ta and Zr-Nb-Y trianglar diagrams and the environmental discrimination diagrams of incompatible ele-ment distribution pattems,the authors have drawn some conclusions that are different from those by previous workers.It is concluded that volcanic rocks in the Laochang Ag polymetallic deposit at Lancang,Yunnan belong to continental within-plate alkali basalts, and that their geotectonic setting seems to be at the northeastern margin of East Gondwana Land.     

中国东南部晚中生代-新生代玄武岩与壳幔作用

中国东南部的火山活动在早中生代时期仅有很小规模,晚中生代最早的、较大规模的岩浆活动始于中侏罗世早期,至早白垩世是火山岩浆活动的鼎盛期,在近100个Ma的时间内形成了大面积分布的晚中生代火山-侵入岩,而在新生代则以面积较小的玄武岩浆喷出活动为主,局限分布于沿海一带。以晚中生代湘南、赣南和闽西南的近EW向火山岩带和浙、闽沿海地区的近NNE向火山岩带,以及新生代近NNE向火山岩带为研究对象,对这些火山岩的地球化学特征对比研究,结合时空分布,讨论了它们的起源及其与壳幔相互作用的关系,以及它们形成的构造环境,其结果显示,EW向晚中生代火山岩带（180～170Ma）的西段玄武岩独立产出,且明显属碱性系列;而中段和东段玄武岩和流纹岩伴生,其中的玄武岩均为亚碱性系列的拉斑玄武岩。它们形成于板内拉张构造环境,是中国东南部特提斯构造域向太平洋构造域转换、晚中生代大规模岩浆作用的序幕。研究表明,该火山岩带自西向东表现出不同程度的壳幔相互作用,玄武岩在成岩过程中有少量陆壳组分加入。NNE向晚中生代火山岩带（130～90Ma）主要为流纹质岩石,安山岩和玄武岩很少。即使是双峰式火山岩也以酸性岩为主,玄武岩仅占全部火山岩体积的30％以下。其中的玄武岩主要属钙碱性系列,少数属拉斑系列。它们形成于火山弧构造环境,是中国东南部受太平洋构造域影响发生大规模火山岩浆作用的主旋律。其中玄武岩岩浆成分受到了较高程度的陆壳物质混染,同时代的中性火山岩是由底侵的玄武岩岩浆和陆壳物质来源的酸性岩浆发生岩浆混合作用而形成的,反映了强烈的壳幔相互作用。NNE向新生代火山岩带,分布在浙闽沿海,以碱性系列玄武岩为主,均含幔源包体,并受NNE向大陆边缘断裂构造的控制。它们形成于板内裂谷环境,是中国东南沿海由晚中生代火山弧构造环境转换为新生代板内裂谷环境的标志,起源于软流圈地幔,并有EMII岩石圈地幔的混合组分,但基本没有受到陆壳物质的混染。     

阿尔金山北缘早古生代岩浆活动的构造环境

阿尔金山北缘地处塔里木盆地和柴达木盆地之间的阿尔金断裂的西北,是青藏高原北部边界地区。该区花岗岩类主要形成于早古生代以来,为钙碱性岩系(碱性程度不高),发育Ⅰ型和A型两种花岗岩类,缺少S型花岗岩。早古生代与蛇绿岩伴生的双峰式火山岩系属于亚碱性系列,其中的玄武岩主要为拉斑系列,流纹岩属钙碱系列。花岗岩类构造环境分析和判别结果表明,阿尔金山北缘早古生代处在破坏性活动板块边缘,构造环境可能经历了早古生代活动陆缘的(火山)岛弧、中生代大陆造陆抬升以至新生代的后造山作用演化过程。火山岩类的构造环境分析结果表明,玄武岩类可能具有洋脊区、岛弧区和板内区各种构造环境,流纹岩类则主要处在板内区。以上分析说明早古生代"阿尔金洋"的存在。      

A Lower Palaeozoic shallow water sequence in the eastern European Variscides (SW Poland): provenance and depositional history

The Gackowa Formation of inferred Cambrian —Ordovician age is part of the metamorphosed pre-Variscan basement of the southern Kaczawa Mountains of the Sudetes region, south-west Poland. Previously variously interpreted as lavas, tuffs and sandstones, it is shown to consist of about 200 m of originally well-sorted siliclastic sedimentary rocks within a sequence of predominantly mafic volcanic rocks. Four facies have been distinguished based on relict sedimentary structures and textures and these suggest that deposition took place on a storm-dominated shelf, mostly above the wave base. The petrography, detrital zircon morphologies and geochemistry suggest affinity with, and derivation in large part from, acid volcanic rocks at a comparable stratigraphic position in a separate tectonostratigraphic unit to the south. The Gackowa Formation and its acid volcanic source rocks have a clear continental geochemical signature, in contrast with the mantle-derived basic/bimodal volcanic rocks below and above; it is suggested that the parent acid magma originated by crustal melting during the ascent of these mantle-derived magmas. A continental crust setting is inferred for the deposition of the Gackowa Formation sandstones, thus suggesting a continental setting for the associated within-plate basalts. The entire volcanic/sedimentary succession resembles elements of the Lower Palaeozoic of Germany, and all may have formed in an initial rift setting during Late Precambrian to Ordovician times.     

Stages of Trap Magmatism in the Norilsk Area: New Data on the Structure and Geochemistry of the Volcanic Rocks

A periodic character of the evolution of trap magmatism was inferred by many researchers from the fact that sequences of volcanic rocks consist of alternating units of lava flows and tuff. A new phase of studying magmatic rocks in the Siberian Platform was related to the possibility of apply high-precision geochemical techniques in studying trace elements and Sr, Nd, and Pb isotopic compositions. The use of these techniques made it possible not only to identify small individual cycles in the vertical sections of volcanic rocks but also to distinguish larger stages. The currently most widely acknowledged scenario of the origin of volcanic rocks involves three stages, during which oceanic-island basalts (OIB), transitional series (intermediate between OIB and WPB), and within-plate basalts (WPB) were formed. This scenario was inferred mostly from data on rocks in the western part of the Norilsk area (Kharaelakh Trough). This publication presents recently obtained data on the inner structure of the sequences of volcanic rocks and the geochemistry of basalts in the eastern part of the territory, where no rocks show transitional characteristics have ever been found. They can be classified into two types that have clearly different composition and occur in different areas. These types characterize two major stages of the origin of volcanic rocks: rift-related and trap magmatism itself. The rocks produced during these stages occur at neighboring territories.     

Basaltoids and carbonatite tuffs of Ambinsky volcano (Southwestern Primorye): Geology and genesis

Geological-petrological data were first obtained on the Early Miocene basaltoids and spinel-fassaite carbonatite tuffs of the Ambinsky volcanic structure in southwestern Primorye. The geological study of Ambinsky volcano allowed the reconstruction of stratigraphic sections across lava and pyroclastic basaltic rocks and stratified carbonatite tuffs. The chemical compositions of rocks and mineral phenocrysts from basalts and carbonatite tuffs are reported. The basaltoids are classed with undifferentiated moderately alkaline within-plate basalts. Evidence of carbonate-silicate immiscibility was found in the basaltoids and carbonatite tuffs. It was suggested that the formation of the carbonatite melt associated with simultaneous basification and abundant crystallization of spinel, fassaite, as well as oversaturation of the silicate system in Ca was caused by limestone assimilation, subsequent transformation of the melt, and liquid immiscibility. Thermal decomposition of carbonates with dissolution of released CaO in magma and accumulation of CO₂ in a closed magmatic chamber gave rise to the autoclave gas effect and, correspondingly, heavy explosive eruptions atypical of such volcanic rocks. The genesis of carbonatite tuffs of Ambinsky volcano can serve as a model example of exsolution of carbonate melt in the moderately alkaline nonagpaitic basaltic system.     

新疆甜水海地块种羊场石炭纪火山岩年代学和地球化学:岩石成因和地质意义

甜水海地块西段的种羊场地区发育一套互层状产出的玄武岩-玄武安山岩-流纹岩,本文对其进行了岩石学、同位素年代学和地球化学研究。结果表明,流纹岩LA-ICP-MS锆石U-Pb定年获得三组年龄:343.5±4.1Ma表明火山岩的形成时代为早石炭纪,2439±26Ma和1988±36Ma说明甜水海地块存在前寒武纪结晶基底。其中玄武质岩石岩性从拉斑系列、钙碱性系列向碱性系列过渡,呈现出E-MORB(OIB)、大陆板内拉张和岛弧的混合特征,与典型弧后盆地Okinawa玄武岩有一定的差异,表明其可能是异常陆缘弧后盆地拉张裂解的产物。玄武质岩石和流纹岩的主量元素、稀土元素和微量元素比值对的差异表明它们不是同源岩浆演化的产物,玄武质岩石的源区为类似E-MORB(OIB)的岩石圈地幔,且发生了部分熔融,原始岩浆上升过程中经历了矿物分离结晶和地壳混染作用。流纹岩属于高硅高碱的钙碱性火山岩,是上地壳部分熔融的产物。种羊场早石炭纪火山岩可能代表了古特提洋西端早期扩张的记录,为西昆仑-喀喇昆仑地区晚古生代多岛洋格局提供了新的证据。     

The Devonian magmatism in the Kropotkin Ridge (East Sayan) and sources of basites: geological,geochemical, and Sr-Nd isotope data

In the east of the Tuvinian trough within the Kropotkin Ridge, the formation of Devonian volcanic associations was intimately conjugate with rifting on the southwestern framing of the Siberian Platform. The associations include picrite-like basalts, trachybasalts, basaltic trachyandesites, trachyandesites, trachytes, trachyrhyodacites, trachyrhyolites, comendites, and subvolcanic dolerites. The basic and normal-basic rocks are subdivided into two groups by TiO₂ contents: high-Ti (TiO₂ ～ 2.2–4.2 wt.%) and medium-Ti (TiO₂ ～ 1.3–2.0 wt.%). Compared with the high-Ti basites, the medium-Ti ones are depleted in K, Rb, REE, Nb, Ta, Th, and U and have features of magmatic series of active continental margins. The high-Ti rocks are similar in composition to within-plate basalts. But in the isotopic compositions of Sr and Nd the above groups of basites are similar and correspond to mantle sources forming enriched within-plate basalts of the OIB type. This combination of within-plate and continent-marginal geochemical features in the basites localized in the same structure-geologic conditions might indicate the formation of rock associations in the rift zone at the rear of active continental paleomargin during the evolution of their common plume source. Its interaction with the suprasubductional lithospheric mantle determined the geochemistry of rocks.     

Provenance of temper in a New Kingdom Egyptian pottery sherd: Evidence from the petrology and mineralogy of basalt fragments

A New Kingdom spinning bowl from Karnak (Luxor) Egypt is similar in form to spinning bowls commonly found at other Egyptian sites and has a bulk chemical composition in the range for other Egyptian marl vessels. These data support a domestic origin. The matrix of the bowl contains unaltered, sand-sized, mafic rock fragments with volcanic, subophitic textures. Over 20% of the sand-sized grains consist of angular, unweathered rock fragments, and of these ∼20% are volcanic. Apparently they were added as temper. Electron microprobe analyses show that augite, plagioclase, and, where present, pigeonite, in nine of these have compositions typical of mafic igneous rocks. Geothermometry confirms crystallization at ∼1100°C. Pyroxene discrimination diagrams indicate geological sources ranging from within-plate alkali basalts to within-plate, continental tholeiites. Suitable sources for the temper are rare in Egypt. Both alkaline and tholeiitic, postorogenic (unaltered) late Cenozoic basalts occur in the Cairo area, making this the most likely but not the only possible source for the temper. The pottery may have also originated in Cairo because raw rock materials were moved upstream less commonly than down the Nile. A Cairo provenance for the Karnak artifact is consistent with the everyday movement of people and goods along the Nile between the ancient twin capitals of Memphis and Thebes. These results and the common occurrence of volcanic rocks as temper indicate that microbeam analytical techniques may help narrow the provenance of ancient pottery. © 1998 John Wiley & Sons, Inc.     

济阳坳陷第三纪火成岩地球化学特征研究

对济阳坳陷第三纪火成岩样品进行了系统的地球化学分析,分析结果表明：这些火成岩的SiO₂含量较低（大部分低于50%）,属于基性火成岩,岩石类型主要为玄武岩和粗面玄武岩。绝大部分样品的TiO₂含量较高,为1.64%～2.09%,不同于TiO₂含量较低的岛弧火山岩。碱性样品和亚碱性样品数量相当,Na₂O含量都高于K₂O含量,Na₂O/K₂O最高可达2.75。这些样品具有富集大离子亲石元素（LILE）如Rb和Ba,亏损重稀土元素（HREE）如Yb和Lu。具有右倾的球粒陨石标准化稀土元素配分模式和原始地幔标准化不相容元素分布模式。源区分析表明,这些火成岩的源区为富集的受过流体交代的岩石圈地幔。运用不活动元素对这些样品进行了构造环境的判别,结果表明这些样品的主体形成于板块内部环境。     

阿拉善北部地区石炭纪火山岩岩石成因及构造意义

阿拉善北部地区石炭纪火山岩分布广泛, 目前对其成因和构造环境研究还很薄弱.通过对该区石炭纪火山岩岩石学和地球化学特征的分析, 探讨其岩石成因和形成时的构造背景, 为判定石炭纪盆地性质与古构造环境提供岩石地球化学约束.研究区内石炭纪火山岩主要为中-酸性火山岩, 少量基性火山岩.玄武岩、玄武安山岩的大多数样品显示亚碱性系列特征, Mg#介于0.29~0.69之间, 高场强元素Nb、Ta、Ti明显亏损, 岩石轻度富集轻稀土元素(LREE), (La/Yb)_N=2.19~10.10, Eu异常不明显(δEu=0.81~1.08), 稀土配分曲线右倾较缓, ε_Nd(t)值较高(+1.10~+6.35).总体上既显示板内构造环境特征, 又携带俯冲带地球化学印记.综合区域地质特征及前人研究结果, 认为阿拉善北部及其邻区石炭纪火山岩形成于板内裂谷环境, 且可能与地幔柱事件有关, 岩浆在上升过程中受到地壳物质不同程度的混染.      

Late Triassic siliceous-volcano-terrigenous deposits of the Chukchi Peninsula: composition of igneous rocks,U-Pb age of zircons,and geodynamic interpretations

Study of Late Triassic volcanic, subvolcanic, and volcanosedimentary rocks of the Chukchi Peninsula (Vel’may terrane) has shown their different geochemical types. Basalts, dolerites, and tuffs of the lower-middle strata of the Upper Triassic section bear evidence for their formation in suprasubductional geodynamic setting. Basalts and dolerites of the upper strata of this section correspond in composition to within-plate rocks and are similar to Middle-Late Triassic oceanic-plateau basalts and dolerites. U-Pb dating of magmatic zircons from tuffs of the lower-middle strata and from dolerites of the upper strata shows the almost synchronous magmatic activity in the suprasubductional (206 ± 5 Ma) and within-plate (212 ± 4 Ma) geodynamic settings.     

The western Durkan Complex (Makran Accretionary Prism,SE Iran): A Late Cretaceous tectonically disrupted seamounts chain and its role in controlling deformation style

The Durkan Complex is a key tectonic element of the Makran accretionary prism (SE Iran) and it has been interpreted as representing a continental margin succession. We present here a multidisciplinary study of the western Durkan Complex, which is based on new geological, stratigraphic, biostratigraphic data, as well as geochemical data of the volcanic and meta-volcanic rocks forming this complex. Our data show that this complex consists of distinct tectonic slices showing both non-metamorphic and very low-grade metamorphic deformed successions. Stratigraphic and biostratigraphic data allow us to recognize three types of successions. Type-I is composed by a Coniacian – early Campanian pelagic succession with intercalation of pillow lavas and minor volcaniclastic rocks. Type-II succession includes a volcanic sequence passing to a volcano-sedimentary sequence with Cenomanian pelagic limestones, followed by a hemipelagic sequence. This succession is characterized by abundant mass-transport deposits. Type-III succession includes volcanic and volcano-sedimentary sequences, which are stratigraphically covered by a Cenomanian platform succession. The latter is locally followed by a hemipelagic sequence. The volcanic rocks in the different successions show alkaline geochemical affinity, suggesting an origin from an oceanic within-plate setting. Our new results indicate that the western Durkan Complex represents fragments of seamounts tectonically incorporated in the Makran accretionary wedge during the latest Late Cretaceous–Paleocene. We propose that incorporation of seamounts in the frontal prism caused a shortening of the whole convergent margin and possibly contributed to controlling the deformation style in the Makran Accretionary Wedge during Late Cretaceous–Paleocene times.     

峨眉山大火成岩省东区普安玄武岩系年代学、地球化学及成因研究

广泛分布于中国西南川、滇、黔三省的峨眉山玄武岩是我国最早被国际认可的大火成岩省,受到了国内外学者的广泛关注。前人对大火成岩省西区玄武岩已达成多项共识,而对东区玄武岩的岩石组合、火山活动时限、岩石成因等方面还存在诸多争议。本文以峨眉山大火成岩省东区贵州普安玄武岩系为研究对象,通过解析典型剖面,明确该区玄武岩系岩石类型从底到顶总体为第1旋回的爆发相火山角砾岩、第2旋回的溢流相玄武岩以及第3旋回的火山沉积相凝灰岩。玄武岩系顶部凝灰岩锆石LA-ICP-MS U-Pb测年结果限定了大火成岩省东区火山活动时间持续上限为250 Ma。主微量元素显示该区玄武岩系以高Ti碱性玄武岩为主。玄武岩稀土元素球粒陨石标准化为轻稀土元素富集的右倾曲线模式,Rb和Sr亏损、Ba和Hf富集等特征与贵州地区玄武岩、峨眉山大火成岩省西区高Ti玄武岩以及OIB地球化学特征基本一致。微量元素显示该区玄武岩源区可能为受交代的石榴石地幔橄榄岩,由深部地幔柱上升至石榴石橄榄岩稳定区部分熔融产生熔融体,和富集交代流体的大陆岩石圈地幔混合形成,岩浆上升运移过程中发生了一定程度分离结晶作用和微弱地壳混染作用。研究表明,峨眉山大火成岩省东区普安玄武岩系形成于峨眉山地幔柱边部埋深较大、低程度部分熔融以及高压的环境。