Multiple Phases of Mafic Magmatism in Gyangze-Kangma Area: Implications for the Tectonic Evolution of Eastern Tethyan Himalaya

A number of E-W trending subparallel mafic dikes of diabase composition occurred in Gyangze-Kangma area,eastern Tethyan Himalaya,southern Tibet.They intruded into the Tethyan Himalaya sedimentary sequence.Whether they belong to the;32 Ma Comei LIP（Zhu et al.,2009）or

Mineralogy, Geochemistry and Palaeomagnetism of Mafic Dykes from Kumaun Lesser Himalaya: Implication on Petrogenesis, Tectonic Setting and Timing of Mafic Magmatism in Northern Part of Indian Lithosphere

Occurrence of mafic dykes in Himalaya has been intriguing and debated since long because of its difficulty to ascent and emplacement through a thickened crust.Mafic dykes in Kumaun Lesser Himalaya(KLH)of central Indian

Precambrian Mantle Characteristics as Recorded by the Episodic Mafic Magmatism in the Liaodong Peninsula

1 Introduction Mafic rocks are widespread throughout the Liaodong Peninsula and vicinity,northeastern North China Craton,providing important constraints on their mantle source characteristics of individual episodes,as they have

Spatiotemporal mapping of(ultra‐)mafic magmatic mine areas:Implications of economic and political realities in China

The spatiotemporal extension/expansion of mine areas is affected by multiple factors.So far,very little has been done to examine the interaction between mine areas and political or economic realities.The(ultra‐)mafic magmatic mines in China played a specific role in supporting national development and providing an ideal research subject for monitoring their interrelationship.In this study,remote sensing and mining‐related GIS data were used to identify and analyze 1233(ultra‐)mafic magmatic mine area polygons in China,which covered approximately 322.96 km2 of land and included a V–Ti–Fe mine,a copper–nickel mine,a chromite mine,an asbestos mine,and a diamond mine.It was found that(1)the areal expansion of mines is significantly related to the mine types,perimeter,topography,and population density.(2)The mine area variation also reflects market and policy realities.The temporal expansion of the mine area from 2010 to 2020 followed an S‐shaped pattern(with the turning point occurring in 2014),closely related to iron overcapacity and tightened mining policies.(3)The complexity(D)of the mine area may reflect mine design and excavation practices.To be specific,lower D indicates early‐stage or artisanal/small‐scale mining,whereas higher D represents large‐scale mining.This study demonstrates that the detailed mapping of mine land can serve as an indicator to implement miningrelated market and policy changes.The(ultra‐)mafic mines area data set can be accessed at https://zenodo.org/record/7636616#.Y-p0uXaZOa0.

Post-collisional mafic magmatism:Record of lithospheric mantle evolution in continental orogenic belt

In order to better understand the role of post-collisional mafic magmatism at convergent plate boundaries in revealing the earth’s evolution,this paper has systematically summarized the research history of post-collisional mafic magmatism,different types of collision and their influence on the nature of orogenic mantle,the concept and implication of post-collisional magmatism,and the relationship between post-collisional mafic magmatism and orogenic mantle evolution and mineralization.Post-collisional mafic igneous rocks are not only the direct records for studying the nature and evolution of orogenic mantle,but also the important carriers for regional mineralization.However,the type and quantity of the crustal materials involved in modifying the overlying lithospheric mantle during collisional orogeny,the process and mechanism of such modification,and the major control factors and mechanism of mafic magmatism-related mineralization during the post-collisional period are the main contents and direction of future researches in this field.Therefore,the study of post-collisional mafic magmatism is of significant implications for developing the theory of plate tectonics.

Mantle Source Components and Magmatic Evolution for the Comei Large Igneous Province:Evidence from the Early Cretaceous Niangzhong Mafic Magmatism in Tethyan Himalaya

The Niangzhong diabase dikes,dated at 138.1±0.4 Ma,are located within the outcrop area of the Comei large igneous province(LIP).These diabase samples can be divided into two groups:samples in Group 1 show varying MgO(1.50 wt.%-10.25 wt.%)and TiO_(2)(0.85 wt.%-4.63 wt.%)contents,and enriched initial isotope compositions(^(87)Sr/^(86)Sr(t)=0.7056-0.7112,ε_(Nd)(t)=-0.3-+3.8),with OIB-like REEs and trace elements patterns,resulting from low degree melting of garnet-bearing lherzolite mantle sources;in contrast,samples in Group 2 show limited MgO(4.14 wt.%-7.75 wt.%)and TiO_(2)(0.98 wt.%-1.69 wt.%)contents,and depleted initial isotope compositions(^(87)Sr/^(86)Sr(t)=0.7075-0.7112,ε_(Nd)(t)=+5.5-+6.2),with N-MORB-like REEs and trace elements patterns,resulting from relatively high degree melting of spinel-bearing lherzolite mantle source.Combined with the published representative data about Comei LIP,we summarize that the source components for Comei LIP products include OIB end-member,enriched OIB end-member,and N-MORB end-member,respectively.Melts modeling suggests that magmas in the Comei LIP evolve in a relatively high oxygen fugacity condition,which influenced their fractionation sequences and led to systematic changes of TiO_(2)contents,Ti/Y and Ti/Ti*ratios.From the spatial and temporal distribution of above three end-member samples,deep process of Kerguelen plume during the Comei LIP formation can be interpreted as the interaction among the Kerguelen plume,the overlying lithospheric mantle,and the upwelling asthenosphere.The magmatism of Comei LIP began at~140 Ma and then lasted and peaked at~132 Ma with the progressively lithospheric thinning of eastern Gondwana upon the impact of Kerguelen plume.

Geochemistry and geochronology of mafic rocks from the Spanish Central System:Constraints on the mantle evolution beneath central Spain

The Spanish Central System(SCS)contains several suites of Palaeozoic mafic igneous intrusions with contrasting geochemical affinity:Ordovician tholeiitic metabasites,Variscan calc-alkaline gabbros(Gb1)and microdiorites(Gb2),shoshonitic monzogabbros(Gb3)and alkaline diabases and lamprophyres(Gb4).Not all of these rocks are accurately dated,and several aspects of their genesis are still poorly understood.We present new whole-rock geochemical data(major and trace elements,and Sr-Nd isotopes),U-Pb and Lu-Hf isotopic ratios on magmatic zircons and 40 Ar/39Ar amphibole geochronology results in order to establish a precise chronology for the successive events of magmatism in the SCS,and discuss the nature of their mantle sources.Accurate ages have been determined for the Variscan gabbros(305-294 Ma),the microdiorites(299 Ma)and the accompanying felsic porphyries(292 Ma),the shoshonitic monzogabbros(285 Ma),and the alkaline diabases(274 Ma)and monzosyenites(271-264 Ma).According to this information,the Variscan mafic magmatism would be mainly concentrated in the range of 305-294 Ma,with a final manifestation represented by the minor shoshonitic dykes.The alkaline magmatism proved to be slightly older than previously thought and yielded at least two distinct pulses:diabases and lamprophyres-monzosyenites.Zircon Hf isotopes evidence the involvement of depleted and slightly enriched mantle sources.The bulk of the eHf values are in the broad range of-8 to+11,indicative of melting both depleted and enriched mantle regions.The high within-sample Hf isotope variation(up to-11 epsilon units)shown by samples from the Variscan series(gabbros,microdiorites and monzogabbros)could be explained mainly by hybridisation of magmas derived from heterogeneous lithospheric mantle sources.Pressure estimates indicate that the Variscan mafic magmas were extracted from the lithosphere.The Nd-Hf isotopic composition of these suites of rocks suggests the recycling of pelitic sediments during the Cadomian orogeny.Deeper(asthenospheric)mantle levels were involved in the generation of the alkaline suite,whose anomalous negative eHf values(moderately decoupled with respect to radiogenic Nd)could be associated with subducted oceanic components raised by mantle upwelling associated with lithosphere thinning and extension during the Permian.

2.2Ga Subduction-Related Mafic Magmatic Rocks in the Kongling Complex:Evidence for the Assembly of the Columbia Supercontinent

Objective Petrogenesis of the Paleoproterozoic mafic dikes and their tectonic implications are of great significance to the tectonic evolution of the Yangtze craton as well as the paleoposition of the Yangtze craton relative to the Columbia supercontinent.Till now,

Crust-derived felsic magmatism in the Emeishan large igneous Province:New evidence from zircon U-Pb-Hf-O isotope from the Yangtze Block,China

Numerous intrusive bodies of mafic–ultramafic to felsic compositions are exposed in association with volcanic rocks in the Late Permian Emeishan large igneous province(ELIP),southwestern China.Most of the granitic rocks in the ELIP were derived by differentiation of basaltic magmas with a mantle connection,and crustal magmas have rarely been studied.Here we investigate a suite of mafic dykes and Ⅰ-type granites that yield zircon U-Pb emplacement ages of 259.9±1.2 Ma and 259.3±1.3 Ma,respectively.The εHf(t)values of zircon from the DZ mafic dyke are–0.3 to 9.4,and their corresponding TDM1 values are in the range of 919–523 Ma.The εHf(t)values of zircon from the DSC Ⅰ-type granite are between–1 and 3,with TDM1 values showing a range of 938–782 Ma.We also present zircon O isotope data on crust-derived felsic intrusions from the ELIP for the first time.The δ18O values of zircon from the DSC Ⅰ-type granite ranges from 4.87‰to 7.5‰.The field,petrologic,geochemical and isotopic data from our study lead to the following salient findings.(i)The geochronological study of mafic and felsic intrusive rocks in the ELIP shows that the ages of mafic and felsic magmatism are similar.(ii)The DZ mafic dyke and high-Ti basalts have the same source,i.e.,the Emeishan mantle plume.The mafic dyke formed from magmas sourced at the transitional depth between from garnet-lherzolite and spinel-lherzolite,with low degree partial melting(<10%).(iii)The Hf-O isotope data suggest that the DSC Ⅰ-type granite was formed by partial melting of Neoproterozoic juvenile crust and was contaminated by minor volumes of chemically weathered ancient crustal material.(iv)The heat source leading to the formation of the crust-derived felsic rocks in of the ELIP is considered to be mafic–ultramafic magmas generated by a mantle plume,which partially melted the overlying crust,generating the felsic magma.

Minto Large Igneous Province: A 2.00 Ga Mafic Magmatic Event in the Eastern Superior Craton Based on U-Pb Baddeleyite Geochronology and Paleomagnetism

A precise U-Pb baddeleyite age of 1999±2 Ma has been obtained for the NNW trending Lac Shpogan dyke swarm of the James Bay area of the eastern Superior craton.Previously the age of the swarm was only

Origin and intraplate tectonic setting of mafic magmatic enclaves from the Ngaoundal area,Adamawa-Cameroon:Insights from petrography and geochemistry

In this contribution,detailed field descriptions together with petrographic and bulk-rock major,trace and rare earth elements(REE)data are used to constrain the origin and geodynamic setting of the mafic magmatic enclaves(MMEs)recently discovered within the Pan-African Ngaoundal pluton,Adamawa area,central Cameroon.The investigated MMEs are dark-colored with chilled margins,and display medium to coarse-grain igneous textures.The mineral assemblage is either dominated by K-feldspar and carbonate(group Ⅰ),or by amphibole and plagioclase(group Ⅱ),though the overall mineral phases made of amphibole,plagioclase,K-feldspar,and biotite are similar to that of their host syenite but in different proportions.The MMEs in Ngaoundal area are foid-gabbro in composition with SiO_(2) contents ranging between 41.52% and 43.74% and are contiguous with their host granitoids of intermediate composition(SiO_(2)=57.52% to 58.98%).The host granitoid rocks are metaluminous,and belong to the shoshonitic series.Petrographic and geochemical data have revealed that the Ngaoundal MMEs derived from rapid cooling of hot injected lithospheric mantle-derived magma within cooler host granitoids magma and were emplaced in the intraplate geodynamic setting.

Magma mixing dynamics in a vertically zoned granitic magma chamber inferred from feldspar disequilibrium assemblage and biotite composition: a case study from the Mikir Massif,eastern India

The Kathalguri Pluton is a granitic pluton confined within the Palaeo-Mesoproterozoic Shillong Group of rocks in the Mikir Massif, eastern India. The pluton is vertically zoned characterized by lower medium-to coarsegrained equigranular to porphyritic granite and upper finegrained equigranular granite. Small to large mafic magmatic enclaves(MME) are distributed within the lower granite, while homogeneous grey-coloured hybrid rocks dominate the upper granite. From field relationships, textural features, and mineral chemical analyses we infer that the Kathalguri Pluton was a vertically zoned felsic magma chamber that was intruded by mafic magma during its evolution. The lower portion of the magma chamber was occupied by crystal mush, while the upper portion was dominated by melt when mafic magma intruded it. The occurrence of upper and lower zonations was probably brought about by fractional crystallization. The presence of such zonations within the felsic reservoir caused the mafic magma to interact with the two distinct zones differently,forming MME in the lower granite and homogeneous hybrid rocks in the upper portion. The plagioclase compositions of the larger MME, smaller MME, hybrid rocks,and granitic host rocks vary between An;–An;, An;–An;, An;–An;,and An;–An;respectively. The alkali feldspar compositions of the hybrid rocks range from Or;to Or;, while that of the host granite varies from Or;to Or;. The biotite is eastonitic and siderophyllitic in composition, while the pyroxene is diopside. The apparent pressure range of biotite crystallization in the granitic rocks was calculated at 1.93 to 2.28 kbar, while the biotite crystallization temperature for the different rock types is in the range of 628 and 759 ℃. Oxygen fugacity estimates from the biotite suggest that the Kathalguri magmas crystallized at fO;conditions above the nickel-nickel oxide(NNO) buffer. Distinct disequilibrium textures indicating mixing and mingling between the mafic and felsic magmas are preserved in the smaller MME and homogeneous hybrid rocks. These textures are mainly found in plagioclase crystals, which include resorbed grains, oscillatory zoned plagioclase, boxy-cellular morphology, and overgrowth texture. Some common magma mingling and mixing textures like quartz ocelli and back-veining are also preserved in the smaller MME. An interesting feature observed in the homogeneous hybrid rocks of our study area is mantled alkali feldspar in which orthoclase is mantled by microcline. We propose that this overgrowth texture formed due to epitaxial crystallization of microcline on orthoclase owing to mixing between the felsic and mafic magmas. Such magma mixing event produces a heterogeneous system that is in an extreme state of disequilibrium and facilitates the epitaxial growth of one feldspar on another. On the other hand, the larger MME of our study domain shows limited interaction with the felsic host as indicated by the replacement of clinopyroxene crystals by amphibole and biotite.

Origin and Tectonic Implications of Post-Orogenic Lamprophyres in the Sulu Belt of China

Lamprophyre dykes that crosscut different types of ultrahigh pressure(UHP)metamorphic rocks are widely distributed in the Triassic Sulu UHP orogenic belt.Although abundant studies have been performed on these dykes,their origin and petrogenesis remain topics of controversy.This study presents the results of a detailed field-based study of petrology,whole-rock geochemistry and zircon U-Pb and Lu-Hf isotopes on lamprophyre dykes exposed in the central Sulu UHP zone,aiming at shedding lights on their petrogenesis and providing clues on the geological evolution of eastern continental China during the Cretaceous.The lamprophyres are typically porphyritic,with phenocrysts dominantly composed of amphibole and clinopyroxene set in a lamprophyric matrix.The dykes have moderate Si O2(47.70 wt.%–60.44 wt.%),variably high Mg O(2.58 wt.%–8.28 wt.%)and Fe2 O3 T(4.88 wt.%–9.26 wt.%)contents with high Mg#of 49–66.Geochemically,they have enriched light rare earth element(REE)and flat heavy REE patterns((La/Gd)N=5.14–10.56;(Dy/Yb)N=1.43–1.54)with negligible Eu anomalies(Eu/Eu*=0.83–1.10),and they show enrichment in large ion lithophile elements(e.g.,Ba and K)but depletion in high-field strength elements(e.g.,Nb,Ti and P).In-situ zircon U-Pb geochronology reveals that the lamprophyres have concordant ages of 120–115 Ma,demonstrating that the dykes emplaced in the Early Cretaceous.These zircons have?Hf(t)values ranging from-26.0 to-11.0.Inherited zircons that occur in the dykes are dated to be Neoproterozoic,in line with the protolith ages of their host(i.e.,the UHP rocks).An integration of these data allows us to propose that the lamprophyres were generated during the Cretaceous,by melting of subcontinental lithospheric mantle-derived metasomatite with enriched chemical compositions underneath the North China Craton.The metasomatite was formed mainly by peridotite-fluid/melt reactions,with the fluids/melts mainly liberated from subducted Yangtze continental crust during the Triassic.Regional extension,lithospheric thinning and mantle upwelling caused by rollback of the subducted paleoPacific plate is considered to account for the generation of the lamprophyres as well as the extensive arc-like magmatic rocks in eastern continental China during the Early Cretaceous.

Comparisons of the Paleo-Mesoproterozoic large igneous provinces and black shales in the North China and North Australian cratons

Comparisons of large igneous provinces(UPs)and black shales from different cratons can provide important constraints on Precambrian paleogeographic reconstructions and a better understanding of the environmental effects of large-scale volcanic events.A comparison of intraplate mafic events mostly interpreted as LIPs or portions of LIPs(LIP fragments/remnants due to continental breakup or erosion)from the North China Craton(NCC)and North Australian Craton(NAC)shows good correlation in the age range from 1800 Ma to 1300 Ma,and four robust age matches at ca.1790-1770 Ma,ca.1730 Ma,ca.1680-1670 Ma and ca.1320 Ma have been identified.Most notably,the coeval ca.1320 Ma Yanliao LIP in the eastern-northern NCC and the Derim Derim-Galiwinku LIP in the NAC are also characterized by similar field occurences and dominantly subalkaline tholeiitic basalts and intraplate geochemical compositions,and are interpreted as portions of the same LIP,separated by continental breakup.Subsequent to 1300 Ma,the NCC and NAC exhibit very different magmatic histories,indicating that separation of these two cratons occurred,likely subsequent to the ca.1320 Ma LIP event.A comparison of Paleo-Mesoproterozoic black shales from the NCC and NAC provides further evidence for close connections between these regions during this period.Black shales of the Chuanlianggou Formation in the northern NCC and the Cuizhuang Formation in the southern NCC were deposited in the age range ca.1650-1635 Ma and can be correlated with ca.1640-1635 Ma black shales in the Barney Creek Formation of the NAC.Deposition of black shales within the Xiamaling Formation in the NCC and the Velkerri and Kyalla formations of the McArthur Basin in the NAC occurred synchronously at ca.1380-1360 Ma.Our results from matching of LIP ages and black shales combined with paleomagnetic data show that the northern-northeastern margin of the NCC was connected to the northern margin of the NAC from ca.1800 Ma to 1300 Ma.This long-lived late Paleoproterozoic to mid-Mesoproterozoic connection lasted for at least 500 million years until separation of the NCC from the NAC between ca.1320 and ca.1230-1220 Ma.