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1.
In southern India the older Precambrian is overlain unconformably in the Cuddapah Basin by the Cuddapah and Kurnool Systems. The former is tilted and unmetamorphosed in the west but eastwards becomes strongly folded and metamorphosed. It contains lavas and sills, particularly in the lower two groups, is intruded by dolerites and at Chelima by diatremes of kimberlitic affinities related to those intruding the older gneisses west of the Cuddapah Basin in the Wajrakarur area. The Kurnool System lacks any igneous rocks; its basal conglomerate is diamondi‐ferous.

Rb‐Sr dating of lava samples from the lowest group of the Cuddapah System shows that the age of the base of the system may be as great as 1,700 m.y. Together with data for a granite which intrudes probable Cuddapah rocks near the disturbed eastern margin of the basin the data imply that the base is unlikely to be younger than 1,555 m.y. Metamorphism affected some lavas at about 1,360 m.y. The diatremes have two ages of intrusion, about 1,225 m.y. and 1,140 m.y., the latter being the age of the Majhgawan pipe near Panna in northern India. Pre‐Kurnool dolerites have an age of 980 ±110 m.y.

The lavas and dolerites show a range of initial 87Sr/86Rb ratios from about 0.704 to 0.708 and possibly 0.712.

The age data suggest that no simple correlation can be made with other Precambrian sequences in northern peninsular India. Deposition of the Cuddapah System appears to have started well before the start of the deposition of the Vindhyan System, while the Kurnool System is coeval with only part of the Upper Vindhyan. The data also suggest that present interpretations of the structural development of the Cuddapah Basin may need some revision.  相似文献   

2.
在印度三个时代不同的地洼区中,出现重要的赋存于沉积岩中的铀矿化作用。这些地洼区是:a)印度南部的元古代库达帕洼地;b)印度东北部梅加拉亚的白垩纪Madadek盆地;c)印度北部的晚第三纪喜马拉雅前渊。库达帕洼地呈新月形,沿南印度克拉通东缘沉积,紧邻东加茨活动带,面积达44,500km~2。该洼地由数个上升、下落断块组成。在这些断块内,浅水砂质(库达帕亚组)和钙质(库尔努尔组)沉积物厚度超过12km,同时从2,000—600Ma,至少有四期粒玄岩墙侵入。铀矿化作用主要呈沥青铀矿(含硫化物)和次生铀矿物形式,沿库达帕洼地面南缘出现于磷质碳酸盐岩和共生物的帕帕格尼组砂质岩、砾岩中。如Tummalapalli、Ammasripall,在梅加拉亚,约200米厚的河流相、海相砂质、泥质沉积物分布于1.5km高的西隆高原南缘的Mahadek盆地。该盆地的铀矿化限于河流相、边缘海相早白垩世“石英粗砂碎屑岩/亚长石砂岩”型Mehadek砾岩中,如Comasahat,Pdensashakap、Domiasiat,并呈沥青铀矿、水硅铀矿、钛钠矿形式。这些矿物与还原剂(如碳、生物成因黄铁矿)紧密共生。在喜马拉雅前渊,铀矿化赋存于河流相锡瓦利克砂岩中,并主要产于锡瓦利克砂岩的下-中或中-上接触面上,如Thein、Morni、Hamirpur,Naugajiarao等地。矿化主要呈沥青铀矿、水硅铀矿(与硫化物共生)和大量次生铀矿物形式——这主要是由于持续至现在的反复的活化作用和沉淀作用。这三个地洼区铀成矿作用的共同特点是河流相沉积物围岩(主要为砂岩,并来源于丰富的酸性源区)、远成热液成矿作用和原始成矿作用时的强烈还原环境。这特征可作为在地洼区寻找赋存于沉积岩中的铀矿化的标志。  相似文献   

3.
The Paraná Basin (1 600 000 km2) is the largest intracratonic basin in southern South America and contains a thick (1300 m) Permo-Carboniferous glacial succession (the Itararé Group). This paper describes over 1700 m of drill core recovered during recent exploration for oil and gas. Itararé Group sediments consist of massive and stratified diamictites interbedded with massive and graded sandstones, and massive and laminated mudstones. Facies are interpreted as the product of sediment gravity flows in a glacially influenced marine basin. Three stratigraphic formations can be defined across the basin, each consisting of a lowermost sandstone-rich member overlain by a diamictite-rich member. Examination of Itararé Group rocks both in core and outcrop shows that depositional processes were influenced by active faulting and downslope resedimentation on relatively steep and unstable substrate slopes. Primary glacial deposits such as tillites and associated striated pavements occur along the present eastern outcrop belt which probably coincided with the eastern basin margin during deposition of the Itararé Group. Ice masses fringing the eastern (southern African) and western (Bolivian) basin margins supplied sediment to the basin in the form of fluvio-glacial deltas, fans and floating ice tongues. This sediment was then resedimented downslope as debris flows and turbidites. Both stratigraphic relationships and the regional distribution of facies types identify a clear pattern of basin subsidence and step-wise expansion by outward faulting within Late Proterozoic mobile belts. The position of successive basin margins can be related to specific lineament structures in the underlying basement. Asymmetric expansion of the Paraná Basin occurred along the northern and southern basin margins during deposition of the Itararé Group; this expansion probably reflects shallow crustal adjustments activated by collisional movements along the Andean margin of South America during the Hercynian Orogeny.  相似文献   

4.
ABSTRACT The Wagwater Trough is a fault-bounded basin which cuts across east-central Jamaica. The basin formed during the late Palaeocene or early Eocene and the earliest sediments deposited in the trough were the Wagwater and Richmond formations of the Wagwater Group. These formations are composed of up to 7000 m of conglomerates, sandstones, and shales. Six facies have been recognized in the Wagwater Group: Facies I-unfossiliferous massive conglomerates; Facies II—channelized, non-marine conglomerates, sandstones, and shales; Facies III-interbedded, fossiliferous conglomerates and sandstones; Facies IV—fossiliferous muddy conglomerates; Facies V—channelized, marine conglomerates, sandstones, and shales; and Facies VI—thin-bedded sheet sandstones and shales. The Wagwater and Richmond formations are interpreted as fan delta-submarine fan deposits. Facies associations suggest that humid-region fan deltas prograded into the basin from the adjacent highlands and discharged very coarse sediments on to a steep submarine slope. At the coast waves reworked the braided-fluvial deposits of the subaerial fan delta into coarse sand and gravel beaches. Sediments deposited on the delta-front slope were frequently remobilized and moved downslope as slumps, debris flows, and turbidity currents. At the slope-basin break submarine fans were deposited. The submarine fans are characterized by coarse inner and mid-fan deposits which grade laterally into thin bedded turbidites of the outer fan and basin floor.  相似文献   

5.
The thermal and mechanical structures of the southern part of the Precambrian Indian Shield have been estimated using available heat flow data and shear stress profiles from olivine rheology. These and other geological, geochronological and geophysical data including deep seismic studies (DSS) profiles of Proterozoic Cuddapah basin on South Indian Shield, are utilized to examine thermal models for the evolution of Precambrian intracratonic, platform basins on the Archean lithosphere of Indian Shield. Evidence of mantle perturbations and cycles of thermal events are documented to be important in the Cuddapah basin's evolution. Haxby et al.'s (1976) thermal model has been shown to explain the Cuddapah basin's flexuring and magnitude of subsidence.  相似文献   

6.
吉林东部中、新生代盆地非常规油气资源及潜力分析   总被引：1，自引：0，他引：1  
通过对吉林东部中、新生代区域构造、盆地地质、沉积背景的综合研究,详细阐述了吉林东部中、新生代盆地非常规油气的类型、分布及其地质特征,认为研究区非常规油气的主要类型为油页岩和煤层气,具有一定的页岩气资源潜力。油页岩主要分布在辉桦盆地、罗子沟盆地、松江盆地、延吉盆地和敦化盆地等盆地中,主要层位为下白垩统大拉子组和古近系桦甸组,主要沉积环境为半深湖-- 深湖环境。煤层气的分布范围较广,主要层位为早、中侏罗世地层和古近纪梅河组、珲春组,集中在珲春盆地、敦化盆地、双阳盆地等煤层较厚、埋藏较浅的盆地中。伊通盆地具有页岩气潜力。  相似文献   

7.
The Ordos basin was developed from Mid-Late Triassic to Early Cretaceous, and then entered into its later reformation period since the Late Cretaceous. Its main body bears the features of an intra-cratonic basin. The basin also belongs to a multi-superposed basin which has overlapped on the large-scale basins of the Early and Late Paleozoic. Currently, Ordos basin has become a residual basin experienced reformation of various styles since the Late Cretaceous. It＇s suggested that there were at least four obvious stages of tectonic deformations existing during the basin＇s evolution, dividing the evolution and sedimentation into four stages. The prior two stages were of the most prosperous, during which the lake basin was broad, the deposition range was more than twice larger than the current residual basin, resulting in major oil- and coal-bearing strata. The two stages were separated by regional uplift fluctuations in the area. At the end of the Yan＇an Stage, the depositional interruption and erosion were lasting for a short period of time. The third one is the Mid- Jurassic Zhiluo-Anding stage, in which the sedimentation extent was still broad but the lake area was obviously reduced. In the Late Jurassic tectonic deformation was intensive. A thrust-nappe belt was formed on the basin＇s western margin while conglomerate of different thickness were accumulated within the foredeep of the eastern side. The central and eastern parts of the basin were subject to erosion and reformation. A regional framework with ＂uplift in the east and depression in the west＂ took shape in the area west of the Yellow River. In the Early Cretaceous sediments were widely distributed, unconformably overlapping the former western margin thrust belt and the ridges on the northern and southern borders. There are abundant energy resources such as oil, natural gas, coal and uranium deposits formed in Ordos Basin. The main stages of generation, mineralization and positioning of the multiple energy resources have obvious responding co  相似文献   

8.
Banded iron formations (BIF) are prominent in sediments older than 2 Ga. However, little is known about the absolute abundance of BIF in Archean and Early Proterozoic sediments, and the source of the Fe is still somewhat uncertain. Also unknown is the role that Fe may have played in the maintenance of low oxygen pressures in the Archean and Early Proterozoic atmosphere. An analysis of the chemical composition of Precambrian rocks provides some insight into the role of Fe in Precambrian geochemical cycles. The Fe content of igneous rocks is well correlated with their Ti content. Plots of Fe vs. Ti in Precambrian sandstones and graywackes fall very close to the igneous rock trend. Plots of Fe vs. Ti in Precambrian shales also follow this trend but show a definite scatter toward an excess of Fe. Phanerozoic shales and sandstones lie essentially on the igneous rock trend and show surprisingly little scatter. Mn/Ti relations show a stronger indication of Precambrian Mn loss, perhaps due to weathering under a less oxidizing early atmosphere. These data show that Fe was neither substantially added to nor significantly redistributed in Archean and early Proterozoic sediments. Enough hydrothermal Fe was added to these sediments to increase the average Fe content of shales by at most a factor of 2. This enrichment would probably not have greatly affected the near-surface redox cycle or atmospheric oxygen levels. Continued redistribution of Fe and mixing with weathered igneous rocks during the recycling of Precambrian sediments account for the excellent correlation of Fe with Ti in Phanerozoic shales and for the similarity between their Fe/Ti ratio and that of igneous rocks.  相似文献   

9.
Structural trends in the upper Proterozoic Cuddapah basin, at the basement level and at the Moho level have been discussed based on Deep Seismic Sounding (DSS) studies. Results of DSS studies along the Alampur-Koniki profile (profile 2 of Fig. 1) crossing the northern part of the Cuddapah basin have been discussed in detail. These results, combined with the results of the Kavali-Paranpalle section of the Kavali-Udipi DSS profile (profile 1 of Fig. 1, Kaila et al., 1979) crossing the basin on its southern flank, along with geological data and earthquake epicentral locations, are used to explain the structural trends of the area. It has been shown that the Cuddapah basin was first created in its western part by downfaulting of the crustal block between faults 7 and 14 towards the west and fault 6 in the east (Fig. 1). Subsequently, the eastern part was downfaulted against fault 6 before the commencement of upper Cuddapah sedimentation. Further downfaulting towards the north along fault 5 created the Srisailam block. Minor-scale downfaulting between faults 7 and 13 in the west and fault 6 in the east and fault 8 in the north gave rise to the Kurnool sub-basin at a later stage. Similar downfaulting east of fault 9 and north of fault 5 gave rise to the Palnad sub-basin. Both these sub-basins received Kurnool sediments.After the close of Kurnool sedimentation, the blocks between faults 4 and 6 along profile II and between 11 and 6 along profile I were uplifted at the basement level, thus giving rise to the Nallamalai hills and Iswarakuppam dome (Fig. 1). The low-angle thrust fault 3 on the eastern margin of the Cuddapah basin might be a post-Cuddapah phenomenon. The low-angle thrust fault 2 probably occurred in the post-Dharwar period. Faults 1, 17 and 10 near the east coast of India seem to be comparatively younger probably of Mesozoic time, along which the coastal block is downfaulted giving rise to the sedimentary basins.  相似文献   

10.
The Dadaepo Basin is a small Late Cretaceous sedimentary basin in SE Korea, located on the eastern margin of Asia. The basin is an isolated extensional basin situated between the NNE-striking Yangsan and Dongnae faults. The basin-fill sediments, named the Dadaepo Formation, consist of channelized conglomerates and sandstones intercalated with dominantly purple mudstones in the lower part. The upper part is dominated by fine- to coarse-grained tuffaceous sandstones and olive to dark gray mudstones with abundant volcanic interbeds. The formation unconformably overlies dacitic rocks dated at ca. 94 Ma and is overlain by basaltic andesite dated at ca. 69 Ma (Ar–Ar ages). The overall configuration of the strata of the Dadaepo Formation indicates syndepositional tilting of the basin floor to the north-northeast. A number of outcrop-scale faults are observed in the basin-fill sediments, of which the majority are NW-striking normal faults, including syndepositional growth faults. The orientations of mafic (magmatic) and clastic dikes, interpreted as being approximately contemporaneous with the deposition of the Dadaepo Formation, are also nearly parallel to the strikes of outcrop-scale normal faults. All these extensional structures consistently indicate NE–SW extension of the basin and obliquely intersect the basin-bounding Yangsan and Dongnae faults at angles of 40°–60°. It is thus concluded that the Dadaepo Formation was deposited in a pull-apart basin that subsided as a result of NNE-striking sinistral strike–slip faulting in the southeastern part of the Korean Peninsula during the Campanian (Late Cretaceous). This strike–slip faulting was related to north-northwestward oblique subduction of the proto-Pacific (Izanagi/Kula) or Pacific plate under the eastern margin of the Eurasian plate.  相似文献   

11.
LATE CENOZOIC LITHOLOGY AND MAGNETIC POLARITY STRATIGRAPHY IN THE JIUXI BASIN: IMPLICATIONS FOR TECTONIC EVENTS OF THE WEST QILIAN MTtheNationalKeyProjectforBasicResearchandCASProjectforTibetanResearchProject (KZ951 A1 2 0 4 ,KZ95T 0 6 )  相似文献   

12.
A cluster of lamproite dykes are located 1 km west of Vattikod village at the NW margin of the Cuddapah basin, Eastern Dharwar craton, southern India, during the pursuit for locating primary diamond source rocks by adapting multifarious applications. These exotic rocks are emplaced along WNW-ESE to NW-SE trending fractures in the granitic rocks belonging to the Peninsular Gneissic Complex. Ten out of twelve lamproites occur near Vattikod village and one each is located in the vicinity of Marepalli and Gundrapalli villages respectively. These lamproites, though highly altered, contain microphenocrysts of altered olivine, clinopyroxene, phlogopite, leucite and sanidine and translucent to opaque, amoeboid shaped patches of glass set in a groundmass rich in carbonate, phlogopite, serpentine, and chlorite. This new cluster of lamproites constitutes a part of the recently discovered Ramadugu lamproite field. The Vattikod and Ramadugu lamproites, together with those from Krishna lamproite field and the Cuddapah basin, constitute, a wide spectrum of ultrapotassic magmatism emplaced in and around the Palaeo-Mesoproterozoic Cuddapah basin in southern India.  相似文献   

13.
In Bengal basin the subcrop Gondwana sediments occur in N-S trending elongated grabens originated largely by the graben forming tectonisms of the Gondwanaland which overlie the crystalline basement in the sub-surface in an intra-cratonic setup. So far five wells in shelf part of Bengal Basin have penetrated Gondwana sediments, out of which three wells i.e.,G1, G3 and G2 have been drilled up to Precambrian basement. In subcrop Gondwana graben, glacial to glacio-fluvial Talchir Formation of Early Permian age was deposited above the basement. Early Permian Barakar Formation overlies Talchir Formaion. Flood basin model of deposition is postulated for this coal rich unit. In the absence of Barren Measure Formation, coal bearing Raniganj Formation overlies Barakar Formation. The fluvial set up changed over to arid environment during deposition of Panchet/Supra Panchet Formation (undifferentiated). The deposition of Panchet Formation is followed by eruption of doleritic rocks in both subcrop and outcrop Bengal Gondwana whereas lamprophyres are absent in subcrop of Bengal Gondwana. Rifting as well as pull-apart basin model due to transtensional movement is postulated for Gondwana basins. Detailed lithostratigraphic analysis of the core / cutting samples of the Gondwana sediments reveal that the sediments are mainly fine to coarse grained, poorly sorted sandstone. These sediments are characterized as poor reservoir and needs some treatment for permeability enhancement for hydrocarbon production.  相似文献   

14.
Bayana Basin, sited along the eastern margin of the north Delhi fold belt of the Aravalli Craton, contains an ～3000?m-thick sequence comprising one volcanic and seven sedimentary formations of the Delhi Supergroup. The sedimentary units are the Nithar, Jogipura, Badalgarh, Bayana, Damdama, Kushalgarh, and Weir formations in order of decreasing age. Petrographic study of the sandstones as well as major and trace elements (including rare earth elements) and bulk-rock analyses of the shales and sandstones allow the determination of their provenance, source-rock weathering, and basinal tectonic setting. The sandstones are quartz rich and were derived mainly from exhumed granitoids typical of a craton interior. Geochemical patterns of the sandstones and shales are similar. However, trace element abundances are low in sandstones, probably due to quartz dilution. The coarser clastic Damdama and Weir sandstones, which occur at higher stratigraphic levels, have strikingly low trace element concentrations compared with the underlying Bayana and Badalgarh sandstones. All samples show uniform LREE-enriched patterns with negative Eu-anomalies (Eu/Eu*?=?0.16–0.23) and are similar to those of post-Archaean Australian shales (PAAS). However, the (La/Yb) n ratios (averages 11–18) of all the sedimentary units are higher than those of PAAS, except for the Bayana Sandstone, which has low values (average 6.77). The chemical index of alteration (70–78) and the plagioclase index of alteration (87–97) values and the A–CN–K diagram suggest moderate to intense weathering of the source area.

The provenance analyses indicate that basin sedimentation was discontinuous. It received input from a terrain comprising granitoids, mafic rocks, sedimentary sequences, and tonalite-trondhjemite-granodiorite (TTG) suites. The Nithar and Badalgarh sandstones received input from a source consisting predominantly of granitoids. The succeeding Damdama and Weir sandstones received debris from granitoids and TTG in different proportions. The Kushalgarh shale was possibly derived from a source consisting granites and mafic rocks with a TTG component. The pre-existing sedimentary formations also contributed intermittently during the different phases of sedimentation.

Bulk-rock geochemical data suggest Mesoarchaean gneisses and late Archaean granites of BGC/BGGC (Banded Gneissic Complex/Bundelkhand Granitic Gneiss Complex) basement as possible source terrains. These data indicate deposition in a continental rift setting. The coeval formation of many rift-related Proterozoic sedimentary basins in the BGC/BGGC terrain suggests that the North Indian Craton underwent major intracratonic extension during Proterozoic time, probably triggering the break up of Earth's first supercontinent.  相似文献   

15.
Proterozoic mafic potassic and ultrapotassic igneous rocks emplacedin the Cuddapah Basin and Dharwar Craton of the southern Indianshield are among the earliest recorded on Earth. Lamproitesintrude the basin and its NE margin, whereas kimberlites intrudethe craton to the west of the basin. Kimberlites occur in twospatially separate groups: the non-diamondiferous Mahbubnagarcluster that was emplaced at 1400 Ma and is of a similar ageto the Cuddapah lamproites, and the predominantly diamondiferousAnantapur cluster, emplaced at  相似文献   

16.
The Sunwu-Jiayin Basin is located on the Amur River’s right side and comprises four depressions separated by two NE-trending uplifts. The basin is bounded by first-order steep to vertical faults (mostly normal faults) formed under extension conditions. These faults control the structural pattern of the basin. The sedimentary cover of the depressions developed during five stages: extension, early inversion, thermal subsidence, late inversion, and formation of depressions. The Late Paleozoic and Precambrian basement of the Sunwu-Jiayin basin composed of granitoides and metamorphosed shales crops out within the uplifts and plunges within the depressions to a depth ranging from 0.5 to 3.4 km. The basin under consideration is considered to be the southern margin of the Zeya-Bureya Basin according to the conditions of its formation and the structural features.  相似文献   

17.
Extensive horizons of pyritic shale occur in Mid-Proterozoic sediments of the eastern Belt basin, Montana, U.S.A. These pyritic shales are of striped appearance. Laminated pyrite beds alternate with nonpyritic shale beds. Laminated pyrite beds have wavycrinkly internal laminae and are interpreted as mineralized microbial mats. Pyrite is essentially the only sulfide mineral in these shales. Pyritic shale horizons occur along the basin margins, and it is feasible that colloidal iron was introduced by rivers into basin marginal lagoons and then incorporated into microbial mats and reduced to pyrite. The pyritic shales in the Newland Formation show great similarity to those that host the Pb-Zn deposits of Mt. Isa and McArthur River. It is suggested that pyritic shales of this kind are relatively common in Mid-Proterozoic shales, and that the processes that led to the occasional formation of Pb-Zn ore bodies in these shales are not related to those that formed the pyritic shales themselves.  相似文献   

18.
青藏高原东缘新生代构造层序与构造事件   总被引：28，自引：7，他引：28       下载免费PDF全文
新生代龙门山前盆地和盐源盆地是青藏高原东缘龙门山－锦屏山冲断带内及前缘地区发育和保存最好的新生代沉积盆地，本次以地层不整合面和ESR测年资料为主要依据，将该区新生代构造地层序列划分为5个构造层序，即TS1（65－55Ma)、TS2(40-50Ma)、TS3（23－16Ma)、TS4(4．7-1.6Ma)和TS5（0．74－0Ma)，据此将青藏高原东缘新生代构造变形和隆升事件划分为5期，其中TS1与喜马拉雅地体和拉萨地体拼合事件相关，TS2与印亚碰撞事件相关，TS3与青藏高原第一次隆升事件相关，TS4与青藏高原第二次隆升事件相关，TS5与青藏高原第三次隆升事件相关。  相似文献   

19.
We compare the diagenetic evolution of deeply buried Rotliegend (Permian) red bed sandstones at the southern and northern margin of the Central European Basin (CEB) in Germany. Main target is to evaluate the influence of maturation products from hydrocarbon (HC) source rocks during red bed diagenesis. At the southern margin of the CEB, thick coal-bearing Carboniferous source rocks are omnipresent beneath the Rotliegend. They contain dominantly gas-prone terrigenous organic material and some oil source rocks. Hydrocarbons were generated from Late Carboniferous onwards throughout most of basin subsidence. At the northern margin of the CEB, source rocks are almost absent due to deep erosion of Carboniferous rocks and a low TOC of local Lower Carboniferous relics. Early diagenetic processes are comparable at both basin margins. Significant differences in burial diagenetic evolution are spatially correlated to the occurrence of hydrocarbon source rocks. Burial diagenesis at the southern margin of the CEB is characterized especially by bleaching of red beds, major dissolution events, pervasive illite formation, impregnation of pore surfaces with bitumen, and formation of late Fe-rich cements. Almost none of these features were detected at the northern basin margin. Instead, relatively early cements are preserved down to maximum burial depths. This suggests that major diagenetic mineral reactions in deeply buried red bed sandstones are controlled by the presence or absence of maturing hydrocarbon source rocks.  相似文献   

20.
KUMAR  ANIL; GOPALAN  K. 《Journal of Petrology》2005,46(6):1077-1079
Kimberlites intrude the late Archaean eastern Dharwar Cratonin two spatially separate fields (150 km apart, near Mahbubnagarin the north and Anantapur in the south) to the west of theProterozoic Cuddapah Basin in southern India. Two lamproitebodies intrude the thick Cuddapah Basin sediments near Chelimaand Zangamarajupalle, and a third occurs just outside the presentNE margin of the basin near Ramannapeta. Chalapathi Rao et al.(2004) have studied this spatially, and possibly temporally,close association of kimberlites and lamproites to provide insightsinto their genesis and genetic relationship. Although the mainemphasis of their paper is the petrochemical characterizationof these two suites of rocks, they also report Sr–Nd isotopedata for a small subset of samples, which they use to provideconstraints on the nature of the mantle source regions. Of some  相似文献   

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