Tectonic Environments of the Yan-Liao Rift during Earth's Middle Age(1.7～0.75 Ga): Evidence from Mafic Dyke Swarms in Eastern Hebei, North China

During the past decade,generations of Precambrian mafic dykes/sills have been investigated and revealed in the North China Craton(NCC).Researchers identified more than 20 episodes of Precambrian dyke swarms,

Mechanics of Mafic Dyke Swarms and Breakup of Supercontinent

Dyke swarms can be divided into three types:parallel dyke swarms,radiating dyke swarms and fan-shape dyke swarm,for which the mechanisms of formation are different(Fig.1).Parallel dyke swarms form in response

Does Geochronology of Few Dykes of a Swarm are True Representative of All Dykes of the Same Magmatic Event?: Constraints from the Geochemistry and Google^(TM) Earth Image–ArcG IS^(TM) Studies of the Paleoproterozoic Mafic Dyke Swarms of the Eastern Dharwa

A precise dating of a mafic dyke of a swarm in shield areas has great advantage to identify Large Igneous Provinces(LIPs;short-lived,mantle-generated magmatic event)(Bryan and Ernst,2008;Ernst et al.,2010).Such

Large Igneous Provinces, Their Giant Mafic Dyke Swarms, and Links to Metallogeny

Giant mafic dyke swarms are a key component of the feeder system of Large Igneous Provinces（LIPs）,large volume（>0.1 Mkm;;frequently above>1 M km;）,mainly mafic（-ultramafic）magmatic events of intraplate affinity.

Model Forming of Mesoarchean Gridino Mafic Dyke Swarm during Subduction "Mid-Ocean Ridge – Continent"

The high-pressure metamorphosed Gridino dyke swarm comprises a major group of Mesoarchean 2.87-2.82 Ga mafic dykes intruded within the Mesoarchean continental crust of the Kola craton(the Belomorian tectonic province

The Geochemistry of Late Mesozoic Mafic Dyke Swarms in Fujian Province, Southeast China

Mafic dyke swarms is a special geologic terrain in continent,which can provide us abundant geodynamic information,mafic dyke swarms were an important symbol of the lithospheric extension,which were mainly derived

Neoarchaean-Palaeoproterozoic Mafic Dyke Swarms from the Singhbhum Granite Complex,Singhbhum Craton,Eastern India:Implications for Identification of Large Igneous Provinces and Their Possible Continuation on Other Formerly Adjacent Crustal Blocks

The Singhbhum craton of the eastern India consists of the Singhbhum Granite Complex(SGC)and the Chotanagpur Gneissic Complex(CGC)separated by the Singhbhum Mobile Belt(SMB).The CGC is intruded by Mesoproterozoic as well as Cretaceous mafic dykes;in

Guidelines for Preparing Comprehensive Regional Mafic Dyke Swarm Maps

Several regional maps of mafic dyke swarms(e.g.,Buchan and Ernst,2004,2013;Vuollo and Huhma,2005;Peng,2015)have been published in recent years,as well as an earlier global dyke compilation map(Ernst et al.,1996).

Mafic Dyke Swarms: Their Temporality and Bearing on the Secular Evolution of the Earth

Pioneering U-Pb isotopic studies by a small group of workers in the mid-late 1980s demonstrated the feasibility of using rare accessory mineral chronometers in mafic(gabbroic)intrusive rocks.These examples showed that mafic layered intrusions and diabase/dolerite dyke swarms alike crystallized high-temperature

Global Mesozoic and Cenozoic Rift Systems: Constrain on the Tectonic Setting of Mafic Dyke Swarms

The primary tectonic setting of dyke swarms,especially those formed in the pre-Cambrian era,are under controversy(Peng et al.,2005).However,Mesozoic and Cenozoic rift systems,which are supposed to be the

Age and Geochemical Characteristics of Major Mafic Dyke Swarms in the Southern Part of the Siberian Craton

Several generations of mafic dyke swarms of different ages and geochemical characteristics cut Precambrian rocks of the southern part of the Siberian craton(Irkutsk Promontory).Each generation of dykes is related to a

Map of Mafic Dyke Swarms and Related Units of Russia and Adjacent Regions

Work is currently underway to produce a map in Arc GISTM 10 of the mafic dyke swarms and related units(volcanics,sills and layered intrusions)of Russia and adjacent regions at a scale of 1:5,000,000.Over the past

Updated Digital Map of Mafic Dyke Swarms and Large Igneous Provinces in Western Australia

Since 1894,the Geological Survey of Western Australia(GSWA)has released 14 versions of the‘Geological Map of Western Australia’.The latest in this series,published in December 2015,is the first bedrock geology map

Precambrian mafic dyke swarms in the North China Craton and their geological implications

A map of major Precambrian mafic dyke swarms and related units in the North China Craton is compiled, and the features and geological implications of these swarms are demonstrated. The Archean dyke swarms are available to portray the early crustal growth and cratonization. The middle Paleoproterozoic(2200–1850 Ma) swarms and related magmatic series could constrain the tectonic evolution: They approve that the craton was amalgamated by two sub-cratons. The late Paleoproterozoic(1800–1600 Ma), Mesoproterozoic(1400–1200 Ma) and Neoproterozoic(1000–800 Ma) series swarms are important in paleogeographic reconstruction: they indicate that North China might have connected with some of the North European and North American cratons during Proterozoic. Dyke swarms are not only geological timescales and tectonic markers but also evolution indicators of lithospheric mantle: they imply a rejuvenation of the sub-continental lithospheric mantle of North China at 1780–1730 Ma. These swarms occurred with several rifts, including the Hengling(2200–1970 Ma), Xuwujia(1970–1880 Ma), Xiong'er(1800–1600 Ma), Yan-Liao(1730–1200 Ma), and Xu-Huai(1000–800 Ma). Among them, the Xuwujia rift was possibly continental arc associated; whereas the others were intra-continental. In addition, the Xiong'er and Xu-Huai rifts were possibly triple junctions along the present southern and southeastern margins of the Craton, respectively. Different tectonic settings of these rifts and dyke swarms would result in diversified series of ore deposits.

SHRIMP U-Pb dating and Hfisotopic analyses of zircons from the mafic dyke swarms in central Qiangtang area,Northern Tibet

In the "Central Uplift" of Qiangtang,Northern Tibet,a large scale of mafic dyke swarms extended in E-W direction.Zircon SHRIMP U-Pb dating on two representative samples of diabase dyke yield weighted mean ages of 284 ± 3 Ma and 302 ± 4 Ma,respectively,suggesting they emplaced in the Late Carboniferous to Early Permian.Zircon 176Hf/177Hf ratios range from 0.282852 to 0.283041,with εHf(t) values of +12.1 to +12.2 and Hf modal(TDM) ages of ～440―460 Ma.These data indicate that these mafic dykes were mainly derived from the depleted mantle.In addition,geochemical data suggest that these mafic dyke swarms are ofintra-plate origin.Therefore,the mafic dyke swarms represent products during the extensional process associated with the opening of the Paleo-Tethys Ocean in the area.

The discovery of the Neoarchean mafic dyke swarm in Hengshan and reinterpretation of the previous “Wutai greenstone belt”

The structural mapping and section study indicate that the “greenstone belts” in the southern to central parts of Hengshan were intensively sheared and transposed mafic dyke swarm, which originally intruded into the Neoarchean grey gneiss and high-pressure granulite terrain (HPGT). The HPGT is characterized by flat-dipping structures, to the south it became steep and was cut by the Dianmen mafic dyke swarm. After high-pressure granulite-facies metamorphic event, the mafic dyke swarm occurred, and was associated with the extensional setting and reworked by the late strike-slip shearing. The zircon age dating proves that the Dianmen mafic dyke swarm was emplaced during the period between 2499±4 Ma and 2512±3 Ma, followed by late tectonothermal reworking. The Dianmen mafic dyke swarm further documents the extensional episode in the central to northern parts of North China Craton (NCC), providing the important constraint for the limit between Archean and Proterozoic and correlation between NCC and other cratonic blocks of the world.

Mafic dykes swarms from the Chhotanagpur Gneiess Complex, Singhbhum craton, eastern India

The Singhbhum craton of the eastern Indian shield consists of two major crustal provinces viz.,Chotanagpur Gneissic Complex(CGC)and Singhbhum Granite Complex;separated by a Singhbhum Mobile Belt.There

Mesoarchean Gridino Mafic Dykes Swarm of the Belomorian Eclogite Province of the Fennoscandian Shield(Russia)

Two eclogite associations have been recognized within Belomorian TTG gneisses:(1)the subduction-type Salma association and(2)Gridino eclogitized mafic dykes.Protoliths of the Salma eclogites represent a sequence

Breakup of the Neoarchean supercontinent Kenorland:Evidence from zircon and baddeleyite U-Pb ages of LIP-related mafic dykes in the Coorg Block,southern India

The Coorg Block in southern Peninsular India is one of the oldest crustal blocks on Earth that preserves the evidence for continental crust formation during the Paleo-Mesoarchean through subductionrelated arc magmatism,followed by granulite facies metamorphism in the Mesoarchean.In this study,we report for the first time,the'bar codes'of a major Paleoproterozoic Large Igneous Province in the Coorg Block through the finding of mafic dyke swarms.The gabbroic dykes from the Coorg Block,dom-inantly composed of plagioclase-pyroxene assemblage,show a restricted range in SiO_(2)values of 50.04-51.27 wt.%,and exhibit a sub-alkaline tholeiitic nature.These rocks show relatively flat LREE and constant HREE patterns and lack obvious Eu anomalies.Trace element modeling suggests that the dyke swarm was fed from a melt that originated at a shallow mantle level in the spinel stability field.Zircon grains are rare in the gabbro samples and those separated from two samples yielded 207Pb/206Pb weighted mean dates of 2214±12 Ma and 2221±7 Ma.The grains show magmatic features with depleted LREE and enriched HREE and positive Ce and negative Eu anomalies.Baddeleyite grains were dated from five gabbro samples which yielded 207Pb/206Pb weighted mean ages ranging between 2217±7 Ma and 2228±10 Ma.The combined data show a clear age peak at ca.2.2 Ga.The mafic dykes in the Coorg Block show geochemical similarities with ca.2.2 Ga mafic dyke swarms in different regions of the Dharwar and other cratons in Peninsular India and elsewhere on the globe.The data also support the inference that the global mafic magmatism at ca.2.2 Ga was linked with intracontinental rifting of the Archean cratons through mantle upwelling or plume activity.We correlate the mafic dyke swarms in the Coorg Block with attempted rifting of the Neoarchean supercontinent Kenorland.

南秦岭地块紫阳地区早古生代岩石圈伸展规律、动力学机制及基性岩墙成因

南秦岭地块紫阳地区广泛出露早古生代基性岩墙群,其研究具有重要的地球动力学意义。虽然如此,已有相关研究目前主要集中于志留纪基性岩墙群方面,而对早古生代(如,寒武纪、奥陶纪)基性岩墙群的研究仍相对薄弱。从而制约了对南秦岭早古生代岩石圈伸展过程相关问题(如,时空分布规律、地幔性质、动力学机制和相关成矿作用)的总体把握。鉴于尚存的科学问题,本研究选取康家坪、梨树梁、大竹坪、清明寨、苟家山、庙梁上、曾家山和毛坝村的基性岩墙群为研究对象,开展了矿物学、岩石学、锆石U-Pb年代学、地球化学和Sr-Nd-Hf同位素方面的研究,对其精细时代格局、成因及成岩动力学背景进行了系统探讨。研究结果显示,紫阳早古生代基性岩墙以辉绿岩和辉绿玢岩为主,形成时代为奥陶纪(478.8-486Ma),属碱性系列岩石(K_(2)O+Na_(2)O变化范围为4.10%-5.14%)。另外,基性岩墙群具有富集LREE、Rb、Ba、Sr、Nb、Ta、Zr、Hf和Eu(Eu/Eu*=1.13-1.35),亏损HREE、U、Pb和Ti的典型地球化学特征。(87Sr/86Sr)i=0.7044-0.7050、εNd(t)=3.1-3.6、εHf(t)=4.4-12.1,176Hf/177Hf=0.282634-0.282846,暗示基性岩墙为地幔柱作用过程亏损岩石圈或软流圈地幔部分熔融作用的产物。另外,在辉绿岩成岩过程经历了橄榄石和单斜辉石的分离结晶,但地壳混染的影响不明显。