Geochemistry of island arc assemblage in the Eastern Desert of Egypt and the role of Pan-African magmatism in crustal growth of the Arabian–Nubian Shield:A review

Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.

A preliminary analysis of arcuate structures-relationship of the island arc and deep-sea trench to the dip angle of Benioff zone

The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.

ACCRETION OF AN EARLY CRETACEOUS INTRA- OCEANIC ISLAND ARC TO INDIA: EVIDENCE FROM THE YARLUNG ZANGBO SUTURE ZONE

A discontinuous line of ophiolitic bodies occurs along the Yarlung Zangbo Suture Zone (YTSZ), which stretches across southern Tibet and beyond. This zone marks the locus of collision between Eurasia and India in the Early Cenozoic. Should we assume that the entire Tethyan Ocean basin that lay between these two continental blocks was oceanic or might it have been more complex? Fragments of any terranes that developed within this once extensive ocean potentially lie within the YTSZ. Detailed investigations over the past three field seasons reveal the presence of several terranes distributed along this zone. Work is currently underway to analyze the nature of individual terranes and the timing of any inter\|relationships.

MULTIPLE ISLAND ARC-BASIN SYSTEM AND ITS EVOLUTION IN GANGDISE TECTONIC BELT,TIBET

Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is mainly covered by thick Jurassic—Cretaceous system layer. During the Mesozoic to Cenozoic era, strong island\|arc types volcanism and volcanic rocks and intrusive rocks belt.. Geologists had divided the Tibet Tethyan evolution into three or four stages (Huang, Jiqing, 1987; Pan Guitang, Li Xinzheng, 1993), according to the ocean\|land conversion process of Tethyan evolution .The Tethyan evolution and the nature of Gangdise tectonic belt had been well\|studied by geologists (Huang Jiqing, 1987; Deng Wanming, 1984; Xia Daixiang, 1986; Cheng Changlun 1987; ZhouXiang 1993; Pan Guitang, 1996). Studies showed that Gangdise tectonic belt, from upper Paleozoic to Mesozoic era, had been developed alternate multiple island arc\|basin system, and characterized by many basin types and strong tectonic\|magma activity. Based on the study of Gangdise multiple island arc\|basin system, I present another version of Gangdise tectonic belt tectonic units division and evolution here.

Geology and Genesis of Peraluminous Granites in East Tianshan Upper Paleozoic Island Arc Belt

A peraluminous granite belt occurs along the connecting zone between the TurPan-Hami Precambrian block and the Upper Paleozoic island arc belt. Muscovite granite and two-mica granite are the essential lithological components of that belt. All the potassium feldspars inthese granites are microcline. Heavy minerals are dominated by magnetite. SiO2 contents ofthese granites are greater than 73 % with most of the A/NKC values greater than 1.1, norma-tive corundum values greater than 1. Plots of CIPW norms in the (AL-K-Na)-Ca-(Fe2++ Mg)diagram are mostly situated in the plagioclase-cordierite-muscovite region. The rocks are char-acterized by very low contents of minor elements and ΣREE with strong Eu depletion, δ18Ovalues between 6. 69‰ and 7. 0‰, Rb-Sr isochron age of 260. 2 ± 6. 2 Ma and an initial 87Sr/86Sr ratio of 0. 7052. These granites might have been produced by partial melting of moderatelyacidic volcanites and low-maturity sediments in the basement sequences and could be geneticallyconnected with the southward A-type subduction of the Turpan-Hami block following the clo-sure of the Middle Carboniferous back-arc basin.

The Formation Mechanism of Island Arc

The shape of island arc is formed by changing the axis of back-arc basin caused by rock expansion along the long axis of back-arc basin;that is, island arc is driven to bend along the subduction zone, so that the arc-shaped island is formed.Rock expansion along the long axis of back-arc basin is attributed to lower part of continental crust melting (underplating) on the dehydration belt (along the long axis of back-arc basin) due to dehydration of subducted oceanic crust, and the arched melting plane is formed, so that rocks on the melting plane are subject to differentiated temperature rise and differentiated expansion. The length of rock expansion along the long axis of back-arc basin is in direct proportion to the radian of island arc. The arc length of island arc is equal to the sum of the length of the long axis of back-arc basin and the length of rock expansion. The displacement and the arc length of island arc can be calculated according to the length of rock expansion;on the contrary, the length of rock expansion can be calculated according to the displacement or the arc length of island arc. According to the length and the lithology of rock expansion, the value of temperature rise of rocks above the melting plane, the melting thickness (underplating) at the bottom of continental crust and the settlement depth of back-arc basin can be reckoned.

The Vertical Deformation and Horizontal Displacement Fields,Movement, and Seismicity of the Island Arc Tectonics

In this work,the vertical deformation,horizontal displacement,and stress fields of arcuate tectonics are theoretically derived from the horizontal tectonic stress; then the characteristics of tectonic movement,seismicity,and focal mechanism of arcuate tectonics of the entire world are explained.It is pointed out that the island arc and other arcuate tectonics are gradually developed under the displacement and stress fields of the arcuate tectonics and that the under-thrusting action of the ocean plate is secondary.The distance formulas between the volcanic arc and the trench are suggested and also that theoretical results are consistent with actual data.

Late Palaeogene emplacement and late Neogene-Quaternary exhumation of the Kuril island-arc root (Kunashir island) constrained by multi-method thermochronometry

The Kuril islands constitute a volcanic island arc-trench system, stretching from eastern Hokkaido （Japan） to Kamchatka （Russia） along the northwestern Pacific subduction system, The current arc consists of several volcanic islands mainly with Neogene basement and capped by several, predominantly andesitic, active subduction stratovolcanoes, Kunashir Island is the southwestern-most island of the arc, just off the Hokkaido coast and represents the study area in this paper. The island is composed of a Lower Complex of mainly late Miocene to Pliocene volcanic rocks, covered by an Upper Complex of younger （basaltic） andesitic lava flows and tuffs on which currently four active volcanic edifices are built. In the Lower Complex sub-volcanic and deeper-seated intrusives of the so-called Prasolov and Dokuchaev magmatic complexes are found, More differentiated, tonalitic-granodioritic rocks were collected from these small intrusive bodies. An early Oligocene zircon LA-ICP-MS U/Pb age of 31 Ma for the Prasolov Complex was obtained, showing that the basement of Kunashir Island is older than previously thought. Thermochronometry （apatite fission-track and U-Th-Sm/He and zircon U-ThJHe analyses） further shows that the magmatic basement of the island was rapidly exhumed in the Pleistocene to present levels in a differential pattern, with He-ages ranging from 1.9 to 0.8 Ma. It is shown that the northern section of the island was hereby exhumed more intensely.

Huanggang Intrusive Complexin Northern Tongbai Area:Island-Arc Tectonic Environment and Its Geological Significance

The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.

Zircon LA-ICP-MS U-Pb Age and Island-Arc Origin of the Bayanhua Gabbro in the Hegenshan Suture Zone, Inner Mongolia

Objective The Bayanhua Nb-enriched gabbro is newly discovered in the Diyanmiao-Meilaotewula SSZ-type ophiolitic m61ange belt of the Hegenshan suture zone, Inner Mongolia. Nb-enriched arc gabbros are usually believed to result from partial melting of the mantle wedge peridotites metasomatized by slab melts derived from the subducting oceanic slab, which represent arc magmatic markers of the oceanic subduction zone. However, whether the Hegenshan ocean basin of the Paleo-Asian Ocean was in its subduction stage in the Early Permian requires further study for a final conclusion, and what is the evolution process of the oceanic subduction and lithospheric mantle of the Hegenshan suture zone remains speculative for the lack of further definitely petrological and chronological evidence and constraints. Therefore, this study carried out zircon LA-ICP-MS U-Pb geochronology and geochemistry on the Bayanhua Nb-enriched gabbro to discuss its origin, in order to provide new evidence for the tectonic evolution of the Hegenshan suture zone of the eastern Central Asian Orogenic Belt.

Late Triassic bivalves associated with a hydrothermal vent system in the Yidun Island Arc (SW China) of the eastern Tethys

The Yidun Island Arc in the Three Rivers (Jinsha River, Lancang River, Nujiang River) region of southwestern China is one of the most important Kuroko-type volcanogenic massive sulfide deposits (VMS) in China. Intra-arc rifting of Yidun Island occurred during the Late Carnian-Norian when VMS deposits such as the Gacun Pb-Zn-Cu deposit were formed. A bivalve fauna was found in fine-grained tuffaceous slate and in mineralized tuffaceous siltstone containing very high contents of Pb (45.01-103.37 ppm) and Zn (135.78-300.03 ppm) of the upper Tumugou Formation in the Changtai-Gacun volcanic-sedimentary rift basin. Stratigraphically, the bivalve-bearing beds are equivalents of the Gacun Pb-Zn-Cu deposits. The diversity of this bivalve fauna is very low. It consists mainly of the thin-shelled, epibyssate suspension-feeding bivalves Pergamidia eumenea and Parapergamidia changtaiensis, the burrowing large, elongated, suspension-feeding Trigonodus keuperinus and Unionites? sp., and occasional specimens of the endobyssate suspension-feeding Trigonodus? sp. and the deep burrowing suspension-feeding Pleuromya markiamensis. Individuals of the first four taxa are so abundant that the specimens are sometimes concentrated in shell beds, probably indicating a gregarious habit. This bivalve fauna is associated with internal moulds of cylindrical, slightly conical tubes most likely produced by a worm-shaped organism. Composition, morphology, diversity, and high abundance of this fauna, chemical features of the surrounding sediment, and the tectonic setting all suggest that this bivalve fauna lived in a deep-water environment in or around a hydrothermal vent system.

Constraints on early Paleozoic magmatic processes and tectonic setting of Inexpressible Island, Northern Victoria Land, Antarctica

During the Cambrian and Ordovician, widespread magmatic activity occurred in the Ross Orogen of central Antarctica, forming the Granite Harbor Intrusives and Terra Nova Intrusive Complex. In the Terra Nova Intrusive Complex, the latest magmatic activity comprised the emplacement of the Abbott Unit(508 Ma) and the Vegetation Unit(～475 Ma), which were formed in different tectonic settings. Owing to their similar lithological features, the tectonic transformation that occurred between the formation of these two units has not been well studied. Through a detailed geological field investigation and geochemical and geochronological analyses, four types of magmatic rock—basalt, syenite, mafic veins, and granite veins—were identified on Inexpressible Island, Northern Victoria Land. Our SHRIMP(Sensitive High Resolution Ion Micro Probe) zircon U–Pb ages of the basalt and the granite veins are 504.7 ± 3.1 and 495.5 ± 4.9 Ma, respectively. Major-and trace-element data indicate a continental-margin island-arc setting for the formation of these two rock types. The zircon U–Pb ages of the syenite and the monzodiorite veins are 485.8 ± 5.7 and 478.5 ± 4.0 Ma, respectively. Major-and trace-element compositions suggest a collisional setting for the former and an intracontinental extensional setting for the latter. These results elucidate the evolution from subduction to collision and intracontinental extension in Northern Victoria Land during the 20 Ma spanning the late Cambrian–Early Ordovician and improve our understanding of the tectonics and evolution of the Ross Orogen in the Transantarctic Mountains.

Implications of ε_(Nd) -La/ Nb, Ba/Nb, Nb/Th Diagrams to Mantle Heterogeneity─Classification of Island-arc Basalts and Decomposition of EMII Component

A group of εNd-La/Nb, Ba/Nb, Nb/Th diagrams are used to study mantleheterogeneity. Island-arc basalts (IAB) are distributed in a triangle of these diagrams.Three end-member components (the MORB-type depleted mantle, the fiuid released fromsubducted oceanic crust and the sediments from the continental crust) of the source ofIAB may be displayed in these diagrams. Two types of IAB are identified. They areof the two-component type (with little continental sediments), such as the basalts fromAleutians and New Britain, and the three-component type, such as those from Sunda,Lesser Antilles and Andes. In addition, the EMII type mantle-derived rocks may alsobe divided into two groups. One is exemplifled by continental flood basalts and someperidotite xenoliths, similar to IAB, with high La/Nb and Ba/Nb and low Nb/Th ratios.The other includes the Samoa-type oceanic island basalts, with low La/Nb and Ba/Nband high Nb/Th ratios. The corresponding two sub-components of EMII are EMIIM,which is related to the metasomatism of lithosphere mantle by fluids released from thesubducted oceanic crust, and EMIISR, related to the intervention of recycling continentalsediments into the convective mantle.

Newly developed evidence for the original Tethysan island-arc volcanic rocks in the southern segment of the South Lancangjiang Belt

This paper re-describes the characteristics of pre-Ordovician (Pt3) metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province from the aspects of petrographic characteristics, rock assemblage, petrochemistry, REE, trace elements, lead isotopes and geotectonic setting. The metamorphic volcanic rocks maintain blasto-intergranular and blasto-andesitic textures; the volcanic rocks are characterized by a basalt-andesite-dacite assemblage; the volcanic rocks are basic-intermediate-intermediate-acid in chemical composition, belonging to semi-alkaline rocks, with calc-alkaline series and tholeiite series coexisting, and they are characterized by low TiO2 contents; their REE distribution patterns are of the LREE-enrichment right-inclined type; the volcanic rocks are enriched in large cation elements and commonly enriched in Th and partly depleted in Ti, Cr and P, belonging to the Gondwana type as viewed from their Pb isotopic composition; petrochemically the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the region studied.

大地幔楔的两个深部碳循环圈:差异及宜居效应

本文总结评述了西太平洋板块深俯冲及在东亚地幔过渡带滞留和与之相关的晚白垩世和新生代东亚板内玄武岩共同构成的大地幔楔板内深部碳循环圈存在的证据;探讨了大地幔楔板内碳循环圈与岛弧系统碳循环圈在地幔碳酸盐化交代介质、碳酸盐种属、氧化还原反应及碳酸盐化地幔部分熔融发生机制等方面的差异和对显生宙大气氧含量保持稳定及温室效应周期性变化的影响;并指出了定量估计深俯冲碳酸盐歧化反应还原成金刚石而留在地幔过渡带和通过板内玄武质火山返还大气的碳各自所占有比例应是未来需研究的重要课题。

北秦岭饭铺闪长岩的岩石成因及其构造意义

饭铺闪长岩的岩石成因模型可为深入认识北秦岭古生代中性岩浆作用的活动规律及深部过程提供进一步的限定。饭铺岩体两件样品的锆石U-Pb同位素年龄值分别为422.1±5.5 Ma和424.2±5.2 Ma,表明其形成于晚志留世。其锆石的^(176)Hf/^(177)Hf比值介于0.282560~0.282676,ε_(Hf)(t)值介于-8.48~14.45,T_(DM2)为1938~488 Ma。地球化学分析结果显示,饭铺岩体属钙碱性系列,均具有富硅、碱、钙和镁,Mg^(#)值介于41.7~57.4。在微量元素蛛网图中,饭铺岩体具有Nb、Ta、Ti异常。饭铺岩体的稀土总量为117×10^(-6)~171×10^(-6),(La/Yb)_(N)比值范围是6.71~18.1,δEu值介于0.82~0.95,表现为轻稀土元素富集、重稀土元素亏损的配分特征,未显示明显的负Eu异常。饭铺岩体形成于岛弧构造环境,岩浆起源于下地壳,可能受到少量幔源物质的混合,推测是商丹洋向北深俯冲作用的产物。

西准噶尔南部晚石炭世中-酸性火山岩成因机制及其对准噶尔洋闭合时限的约束

西准噶尔地区广泛分布石炭纪岩浆岩类,了解它们的成因和形成机制可为揭示准噶尔洋盆晚古生代构造格局和发展演化以及约束古大洋闭合时限提供重要依据。本文报道了西准噶尔南部哈拉阿拉特山地区晚石炭世中酸性火山岩的岩石学、锆石U-Pb年代学以及地球化学特征。岩石学研究表明其岩性主要为安山岩、英安质安山岩、流纹英安斑岩和流纹岩。LA-ICP-MS锆石U-Pb定年结果表明哈拉阿拉特山地区中酸性火山岩年龄为308~305 Ma,为晚石炭世中晚期。中酸性火山岩均相对富集轻稀土和大离子亲石元素,亏损Nb、Ta等高场强元素,富钠贫钾,属于低钾拉斑中钾钙碱性系列岛弧火山岩。其中安山岩和英安质安山岩具有较高SiO_(2)(56.15%~66.13%)、Al_(2)O_(3)(16.03%~17.94%)、Na_(2)O(3.44%~5.59%)、Sr((364~576)×10^(-6))含量和Na_(2)O/K_(2)O(3.20~6.40)、Sr/Y(33.5~55.6)比值,贫MgO(1.59%~2.68%)、Y((10.0~16.0)×10^(-6))和Yb((1.08~1.83)×10^(-6))的特征,并且具有Eu正异常(δEu=1.09~1.22),属于典型的埃达克岩,是经俯冲的洋壳板片在石榴角闪岩相发生部分熔融而成,且熔融产生的埃达克质熔体在上升过程中未与上覆地幔橄榄岩发生明显交代作用;流纹岩和流纹英安斑岩具有高的SiO_(2)(69.59%~75.03%)和全碱(w(Na_(2)O+K_(2)O)=7.81%~8.89%)、极低的TFe 2O 3(0.94%~1.57%)和MgO(0.12%~0.97%)含量以及弱负Eu异常(δEu=0.63~1.00)等特征,为准铝质I型流纹岩,是下地壳镁铁质岩石部分熔融的产物,很可能有少量幔源岩浆混入。综合本文数据并结合研究区大量前人已发表的岩浆岩类研究成果,认为西准噶尔南部地区在晚石炭世中晚期仍处于岛弧弧后盆地演化体系,准噶尔洋的闭合时限可能至少推迟至早二叠世早期之后。

北秦岭二郎坪群抱树坪组沉积时代与构造环境

二郎坪群抱树坪组作为北秦岭早古生代重要的沉积记录,其研究程度较低。本文通过对抱树坪组内火山岩夹层和花岗斑岩脉进行岩石学、地球化学和锆石U-Pb测年研究,旨在进一步确定其沉积时代与构造环境。研究结果表明:豫西夏馆地区抱树坪组火山岩夹层已变质为(黑云)阳起钠长片岩,常与黑云石英片岩呈“互层状”产出;岩石原岩为安山质凝灰岩,具有相对低的SiO_(2)(52.56%~62.04%)、较高的Al_(2)O_(3)(10.70%~18.55%)、低的MgO(4.06%~6.21%)和FeO^(T)/MgO(1.23~1.81),富集轻稀土元素和大离子亲石元素Rb、Th、U、K,相对亏损高场强元素Nb、Ta、P、Ti,具镁安山质岩石的特点;结合地球化学特征及前人研究认为,抱树坪组可能形成于活动陆缘弧后盆地。获得黑云阳起钠长片岩原岩的结晶锆石U-Pb年龄为446.0±1.7 Ma,以及侵入其中花岗斑岩脉的成岩年龄为430.0±3.0 Ma,首次将抱树坪组的形成时代准确地限定为晚奥陶世至早志留世。综合区域研究成果认为,小寨组和抱树坪组在地层层序和地层时代上符合广义二郎坪群的划分方案,但大庙组、火神庙组及由小寨组和抱树坪组构成的整体三者在形成时代上表现为近于同时性,在空间上主体呈现近平行关系,可能主体属时代大体相当的不同沉积环境的产物;在大地构造属性方面,认为二郎坪群是在约470 Ma之前由于商丹洋向北俯冲而形成的火山岛弧,在470~436 Ma转化为弧后盆地,至约430 Ma之前最终完成消减闭合。

An Example for Arc-Type Granitoids Along Collisional Zones:The Pertek Granitoid,Taurus Orogenic Belt,Turkey

The Pertek granitoid consisting dominantly of diorite, quartz diorite, quartz monzodiorite, tonalite and lesser granite, adamellite and syenite, is considered to form the easternmost continuation of the Central Anatolian Crystalline Complex. Diorite and monzonites of this granitoid complex are cut by the granitic dykes. The Pertek granitoid, in the study area, is found in the Permo-Triassic Keban metamorphic sequence along intrusive and tectonic contacts. Along the intrusive contacts metasomatic mineralizations are common. Granitoids are, depending on the mineralogical composition, low-, middle- high-K subalkaline features. Major oxide-SiO2 variation diagrams show that fractionation (particularly plagioclase, hornblend, pyroxene and olivine fractionation) played an important role on the granitoid formation during a continuous crystallization process. Distribution of the samples from the Pertek granitoid in the tectonic setting diagrams, and their chondrite- and primordial mantle-normalized trace element patterns resemble to the of arc-type granitoids. Trace element and rare earth element compositions indicate that the magma, from which the Pertek granitoid crystallized, derived from a mantle that was enriched by the fluids derived from the subducted slab, however this magma was contaminated by the crust during its intrusion. These geochemical characteristics are also supported by the field observations. The field and geochemical characteristics of the Pertek Granitiod suggest that they are similar to the other granitoids cropping out in the central and eastern Anatolia and they form the lateral continuation of the same magmatic belt.

准噶尔盆地石北凹陷岛弧环境下火山-沉积建造特征及源储发育模式——以石炭系姜巴斯套组为例

准噶尔盆地石北凹陷位于盆地东部的陆梁隆起带北部,前期针对石北凹陷石炭系火山岩圈闭勘探一直未获突破。近期完钻的准北6井揭示了其石炭系姜巴斯套组自生自储型油气藏具有较大的勘探潜力,但以往针对这类储层的成因及分布研究较少。为了深入研究石北凹陷岛弧环境下火山—沉积建造特征及其源储发育模式,在前人研究的基础上,利用钻井岩心、地震及测试资料,结合烃源岩地球化学特征分析,对姜巴斯套组火山—沉积建造、烃源岩特征进行了系统研究,建立了岛弧控制下的火山岩—火山碎屑沉积岩—烃源岩发育模式,以期为具有相同沉积背景的地区油气勘探提供理论依据。研究表明,石北凹陷姜巴斯套组中基性火山岩形成于与俯冲相关的岛弧环境,火山建造主要为近火山口爆发相、近火山口溢流相、远火山口爆发相,沉积建造以岛弧侧翼的扇三角洲相凝灰质砂砾岩、砂岩与远岛弧低洼地带的滨浅海相凝灰质泥岩为主;姜巴斯套组凝灰质泥岩为一套处于成熟—高熟阶段的中等烃源岩,呈北西—南东向条带状分布,厚度分布在100~500 m之间;姜巴斯套组火山岛弧间歇喷发,远岛弧低洼地带凝灰岩与滨浅海凝灰质泥岩互层状分布,凝灰质泥岩与扇三角洲砂砾岩、岛弧火山岩具有良好的源储配置关系,两类储层为下一步重点勘探方向。