Plume-lithosphere interaction in the Comei Large Igneous Province: Evidence from two types of mafic dykes in Gyangze, south Tibet, China

Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Tibet.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

Post-collisional Adakitic Porphyries in Tibet:Geochemical and Sr-Nd-Pb Isotopic Constraints on Partial Melting of Oceanic Lithosphere and Crust-Mantle Interaction

The distribution of Neogene felsic porphyries intruding in earlier granitic batholiths was mainly controlled by north-south-tending rifting zones and normal faults. The main rock types of the felsic porphyries include granodiorite-porphyry, monzonitic granite-porphyry and quartz monzonitic porphyry. The porphyries are characterized by high SiO2 ((?)64.26%) and Al2O3 (>15% at 70% SiO2), low Y and HREE (Yb) contents, strong enrichment of LILE and LERR, especially K and ST. Geochemical features of the porphyries show distinct adakitic magma affinity. Nd, Sr and Pb isotopic compositions of the porphyries form a linear alignment from MORB to EM2, suggesting a mixing of the MORB reservoir with the metasomatized mantle reservoir. Considering also the geochemical characteristics of the porphyries and the sequence of observable structural-thermal-magmatic events at Gangdise, it is thought that the Neogene porphyries were formed by partial melting of dead subducted oceanic crust in a post-collision setting. K-enrichment in the porphyries is attributed to the interaction of slab-derived melts, i.e., adakites, with the metasomatized mantle during the ascent. There might be a delamination of residual eclogites or amphibole eclogites before the eruption of potassic lava on the Tibetan plateau since 13 Ma.

Computational simulation of convective flow in the Earth crust under consideration of dynamic crust-mantle interactions

The finite element method was used to solve fluid dynamic interaction problems between the crust and mantle of the Earth. To consider different mechanical behaviours, the lithosphere consisting of the crust and upper mantle was simulated as fluid-saturated porous rocks, while the upper aesthenospheric part of the mantle was simulated as viscous fluids. Since the whole lithosphere was computationally simulated, the dynamic interaction between the crust and the upper mantle was appropriately considered. In particular, the mixing of mantle fluids and crustal fluids was simulated in the corresponding computational model. The related computational simulation results from an example problem demonstrate that the mantle fluids can flow into the crust and mix with the crustal fluids due to the resulting convective flows in the crust-mantle system. Likewise, the crustal fluids can also flow into the upper mantle and mix with the mantle fluids. This kind of fluids mixing and exchange is very important to the better understanding of the governing processes that control the ore body formation and mineralization in the upper crust of the Earth.

Petrogenesis of the Late Triassic shoshonitic Shadegai pluton from the northern North China Craton: Implications for crust-mantle interaction and post-collisional extension

Latest Permian to Triassic plutons are widespread in the northern North China Craton(NCC); most of them show calc-alkaline, high-K calc-alkaline, or alkaline geochemical features. The Shadegai pluton in the Wulashan area has shoshonitic affinity and I-type character, and is composed of syenogranites containing abundant mafic microgranular enclaves(MMEs). LA-MC-ICP-MS U-Pb data yield weighted mean 206 Pb/238 U ages of 222 ± 1 Ma and 221 ± 1 Ma for the syenogranites and MMEs, respectively, suggesting their coeval formation during the Late Triassic. The syenogranites have high SiO_2(70.42-72.30 wt%),K_2O(4.58-5.22 wt.%) and Na_2O(4.19-4.43 wt.%) contents but lower concentrations of P_2O_5(0.073-0.096 wt.%) and TiO_2(0.27-0.37 wt.%), and are categorized as I-type granites, rather than A-type granites, as previously thought. These syenogranites exhibit lower(^(87)Sr/^(86)Sr)i ratios(0.70532-0.70547) and strongly negative whole-rock εNd(t) values(-12.54 to-11.86) and zircon εHf(t) values(-17.81 to-10.77),as well as old Nd(1962-2017 Ma) and Hf(2023-2092 Ma) model ages, indicating that they were derived from the lower crust.Field and petrological observations reveal that the MMEs within the pluton probably represent magmatic globules commingled with their host magmas. Geochemically, these MMEs have low SiO_2(53.46-55.91 wt.%)but high FeOt(7.27-8.79 wt.%) contents. They are enriched in light rare earth elements(LREEs) and large ion lithophile elements(LILEs), and are depleted in heavy rare earth elements(HREEs) and high field strength elements(HFSEs). They have whole-rock(^(87)Sr/^(86)Sr)i ratios varying from 0.70551 to 0.70564, εNd(t) values of -10.63 to -9.82, and zircon εHf(t) values of -9.89 to 0.19. Their geochemical and isotopic features indicate that they were derived from the subcontinental lithospheric mantle mainly metasomatized by slab-derived fluids, with minor involvement of melts generated from the ascending asthenospheric mantle. Petrology integrated with elemental and isotopic geochemistry suggest that the Shadegai pluton was produced by crust-mantle interactions, i.e., partial melting of the lower continental crust induced by underplating of mantle-derived mafic magmas(including the subcontinental lithospheric mantle and asthenospheric mantle), and subsequent mixing of the mantle-and crust-derived magmas. In combination with existing geological data, it is inferred that the Shadegai pluton formed in a post-collisional extensional regime related to lithospheric delamination following the collision between the NCC and Mongolia arc terranes.

Interaction between protokimberlite melts and mantle lithosphere:Evidence from mantle xenoliths from the Dalnyaya kimberlite pipe,Yakutia(Russia)

The Dalnyaya kimberlite pipe（Yakutia,Russia） contains mantle peridotite xenoliths（mostly Iherzolites and harzburgites） that show both sheared porphyroclastic（deformed） and coarse granular textures,together with ilmenite and clinopyroxene megacrysts.Deformed peridotites contain high-temperature Fe-rich clinopyroxenes,sometimes associated with picroilmenites,which are products of interaction of the lithospheric mantle with protokimberlite related melts.The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe.Coarse granular xenoliths fall on a geotherm of 35 mWm-2 whereas deformed varieties yield a 45 mWm-2）geotherm in the 2-7.5 GPa pressure interval.The chemistry of the constituent minerals including garnet,olivine and clinopyroxene shows trends of increasing Fe~#（=Fe/（Fe＋Mg））with decreasing pressure.This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels.Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals,determined by LA-ICP-MS.Orthopyroxenes,some clinopyroxenes and rare garnets are depleted in Ba,Sr,HFSE and MREE and represent relic lithospheric mantle.Re-fertilized garnet and clinopyroxene are more enriched.The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene.Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets.Olivines show decreases in Ni and increases in Al,Ca and Ti from Mg-rich varieties to the more Fe-rich,deformed and refertilized ones.Minerals showing higher Fe~#（0.11-0.15） are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels.In P-f（O_2） diagrams,garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at-5 log units below a FMQ buffer.However,Cr-poor clinopyroxenes,together with ilmenite and some Fe-Ca-rich garnets,demonstrate a more oxidized trend in the lower part of lithosphere at-2 to 0 log units relative to FMQ.Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite.The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts,which is greater at the base of the lithosphere.

Crust–mantle interaction recorded by Early Cretaceous volcanic rocks within the southern margin of the North China Craton

This study presents new geochronological and geochemical data for Early Cretaceous volcanic rocks in the southern margin of the North China Craton(NCC),to discuss the crust–mantle interaction.The studied rocks include pyroxene andesites from Daying Formation,hornblende andesites and andesites from Jiudian Formation,and rhyolites from a hitherto unnamed Formation.These rocks formed in Early Cretaceous(138–120 Ma),with enrichment in light rare earth elements(REE),depletion in heavy REE and arc-like trace elements characteristics.Pyroxene andesites show low SiO_(2) contents and enriched Sr–Nd–Pb–Hf isotopic compositions,with orthopyroxene phenocryst and Paleoproterozoic(2320–1829 Ma)inherited zircons,suggesting that they originated from lithospheric mantle after metasomatism with NCC lower crustal materials.Hornblende andesites have low SiO_(2) contents and high Mg#(Mg#=100 Mg/(Mg+Fe^(2+)))values,indicating a lithospheric-mantle origin.Considering the distinct wholerock Sr isotopic compositions we divide them into two groups.Among them,the low(^(87)Sr/^(86)Sr)iandesites possess amount inherited Neoarchean to Neoproterozoic(2548–845 Ma)zircons,indicating the origin of lithospheric mantle with addition of Yangtze Craton(YC)and NCC materials.In comparison,the high(^(87)Sr/^(86)Sr)iandesites,with abundant Neoarchean–Paleozoic inherited zircons(3499–261 Ma),are formed by partial melting of lithospheric mantle with incorporation of NCC supracrustal rocks and YC materials.Rhyolites have extremely high SiO_(2)(77.63–82.52 wt.%)and low total Fe_(2)O_(3),Cr,Ni contents and Mg#values,combined with ancient inherited zircon ages(2316 and 2251 Ma),suggesting an origin of NCC lower continental crust.Considering the presence of resorption texture of quartz phenocryst,we propose a petrogenetic model of’crystal mushes’for rhyolites prior to their eruption.These constraints record the intense crust–mantle interaction in the southern margin of the NCC.Given the regional data and spatial distribution of Early Cretaceous rocks within NCC,we believe that the formation of these rocks is related to the contemporaneous far-field effect of the Paleo-Pacific Plate.

Contrasted continental rifting via plume-craton interaction： Applications to Central East African Rift

The East African Rift system （EARS） provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rifr, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plumelithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities （suture zones） along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic （western） and magmatic （eastern） branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to produce simulations that match observations. This result reconciles the passive and active rift models and demonstrates the possibility of development of both magmatic and amagmatic rifts in identical geotectonic environments.

Crust-Mantle Structures and Gold Enrichment Mechanism of Mantle Fluid System

Gold enrichment mechanism of ore-forming fluid is the essenc e of gold metallization. This paper summarizes the distinguishing symbols of man tle fluid and effect of crust-mantle structure on fluid movement. Fluid moving processes include osmosis, surge, gas-liquid alternation and mutation of fluid speed. During fluid movement, gold will be enriched gradually. Finally, a layere d circulatory system is illustrated in this paper.

Petrology and geochemistry of South Mid-Atlantic Ridge(19°S) lava flows:Implications for magmatic processes and possible plume-ridge interactions

The South Mid-Atlantic Ridge(SMAR)19°S segment,approximately located along the line of Saint Helena volcanic chain(created by Saint Helena mantle plume),is an ideal place to investigate the issue whether the ridgehotpot interaction process affected the whole MAR.In this study,we present major and trace elemental compositions and Sr-Nd-Pb isotopic ratios of twenty fresh lava samples concentrated in a relatively small area in the SMAR 19°S segment.Major oxides compositions show that all samples are tholeiite.Low contents of compatible trace elements(e.g.,Ni=239-594 ppm and Cr=456-1010 ppm)and low Fe/Mn(54-67)and Ce/Yb(0.65-1.5)ratios of these lavas show that their parental magmas are partially melted by a spinel lherzolite mantle source.Using software PRIMELT3,this study obtained mantle potential temperatures(Tp)beneath the segment of1321-1348℃,which is lower relative to those ridges influenced by mantle plumes.The asthenospheric mantle beneath the SMAR 19°S segment starts melting at a depth of^63 km and ceases melting at^43 km with a final melting temperature of^1265℃.The extent of partial melting is up to 16%-17.6%with an average adiabatic decompression value of 2.6%/kbar.The correlations of major oxides(CaO/Al2 O3)and trace elements(Cr,Co,V)with MgO and Zr show that the parental magma experienced olivine and plagioclase fractional crystallization during its ascent to the surface.87Sr/86Sr(0.702398-0.702996),143 Nd/144 Nd(0.513017-0.513177)and 206Pb/204Pb(18.444-19.477)ratios of these lavas indicate the mantle source beneath the SMAR 19°S segment is composed of a three-component mixture of depleted MORB mantle,PREMA mantle,and HIMU mantle materials.The simple,binary mixing results among components from plume-free SMAR MORB,Saint Helena plume and Tristan plume show that asthenospheric mantle beneath the SMAR 19°S segment may be polluted by both Saint Helena and Tristan plume enriched materials.The abovementioned mantle potential temperatures,together with the low Saint Helena(<10%)and Tristan(<5%)components remaining in the asthenospheric mantle at present,show that the physically ridge-hotspot interactions at SMAR 19°S segment may have ceased.However,the trace element and SrNd-Pb isotopically binary mixing calculation results imply that these lavas tapped some enriched pockets left when Saint Helena and/or Tristan plume were once on the SMAR during earlier Atlantic rifted history.

大陆下地壳

大陆下地壳是连接岩石圈地幔和上地壳的“纽带”,是地壳与地幔交换最活跃的部位。上地幔与下地壳的部分熔融及下地壳一些岩石的拆沉还可直接导致壳-幔物质的交换、循环与重组。换言之,下地壳是壳-幔作用的一个极其重要的场所,底垫、拆沉、深熔、高级变质和其他作用都在下地壳中发生和实现。然而,下地壳是以往研究地球深部和浅部关系时被“跳”过去的部位,没有得到足够的重视。克拉通化定义为大陆原来混沌的原地壳分异并形成稳定的上地壳和下地壳,并由此构建了稳定的壳-幔结构,这种空前的稳定关系从形成起一直维持到现在,是大陆演化、洋-陆与壳-幔相互作用的基础。在板块边界的造山过程中,如洋-陆的俯冲碰撞特别是陆-陆碰撞,可以形成不同大陆地块的陆壳叠置、加厚、垮塌、拆沉、底垫和重新稳定,在造山带根部形成新的下地壳,即造山带型下地壳。本文重点讨论了克拉通型下地壳演化过程,强调了其动力学意义及其在大陆动力学研究中的重要地位,建议在深地研究和学科布局中给与充分重视。

华南燕山期佛冈–南昆山花岗岩石成因:来自锆石微量元素、H_(2)O含量及Hf-O同位素的约束

华南地区发育大规模与稀有金属成矿相关的燕山期花岗岩,其岩石类型与成因存在诸多争议,厘清这些争议有助于理解华南地区的成矿作用。锆石是花岗岩中常见的副矿物,具有非常稳定的物理化学性质,不容易受后期地质作用影响,可以很好地保存其形成时母岩浆的地球化学信息,从而避免全岩地球化学分析的不足。本研究选取华南地区佛冈–南昆山花岗岩中的锆石进行LA-ICP-MS微量元素和Hf同位素研究,结合SIMS氧同位素和H_(2)O含量等数据,探讨佛冈岩体和南昆山岩体的岩石类型和成因。两个岩体的锆石都呈现LREE亏损、HREE富集、Eu负异常、Ce正异常,以及Zr/Hf>55、Eu/Eu~*>0.005、Hf含量低(<1.2%)等特点,明显不同于高分异I型花岗岩,指示母岩浆分异程度较低。同时,锆石的REE+Y与P含量之间的关系表明它们也不是S型花岗岩。佛冈岩体锆石较高的δ18O值(7.97‰~10.29‰)、富集的εHf(t)值(-13.6~-5.7)、较低的H_(2)O含量(核密度峰值317~412μg/g)以及较高的锆饱和温度(799~800℃)表明,佛冈花岗岩可能是源区有高比例沉积物加入的A型花岗岩。南昆山岩体也具有类似的、但变化范围更大的锆石δ18O值(6.34‰~11.11‰)、εHf(t)值(-11.1~1.1)和H_(2)O含量(297~1253μg/g)。锆石Hf-O同位素和H_(2)O含量分析结果显示,二者均具有壳幔混合的特点,其中南昆山花岗岩源区地幔物质加入比例更大。

Iceland Plume and its Magmatic Manifestations:LIP-Dornr?schen in the North Atlantic

Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.

幔源岩浆成因的实验岩石学约束

作为地幔熔融的直接产物,幔源岩浆的成分和性质忠实地记录了地幔源区的化学组成并能反映其演化过程,为深入理解地球内部的动力学过程和演化历史提供了重要信息。得益于近年来高温高压实验装置和微区分析测试手段的大幅改进,科学家们能够在高温高压条件下正演模拟和记录地幔岩石的物理化学反应,通过控制实验条件和初始物质成分,揭示不同地质环境下的地幔部分熔融机制,约束幔源岩浆的生成和演化过程。本文通过对不同幔源岩浆成因的实验岩石学研究进行系统梳理,总结了单一地幔橄榄岩源区的熔融、地幔源区其他岩石类型的熔融、地幔源区不同岩石的混合熔融三方面相关实验的研究现状、突出进展和存在问题,并结合深地科学的发展方向,对未来有关幔源岩浆成因和壳幔相互作用的实验研究前景进行了展望。

Interaction between subducted continental crust and the mantle --Ⅱ. Sr and Nd isotopic geochemistry of the syncollisional mafic-ultramafic intrusions in Dabie Mountains

The syncollisional mafic\|ultramafic rocks with Nb, Zr, Ti negative anomalies in the North Dabie terrane have Sr and Nd isotopic compositions with EMI features. Their low and variable initial ε Nd values ranging from -2 to -18 are similar to those of their gneissic country rocks and the ultrahigh\|pressure metamorphic rocks in the South Dabie terrane. These Sr and Nd isotopic features are difficult to be interpreted by mantle metasomatism related to oceanic subduction or crust assimilation, but is best explained by the mantle metasomatism related to continental subduction.

Subduction-zone peridotites and their records of crust-mantle interaction

Subduction is the core process of plate tectonics. The mantle wedge in subduction-zone systems represents a key tectonic unit, playing a significant role in material cycling and energy exchange between Earth's layers. This study summarizes research progresses in terms of subduction-related peridotite massifs, including supra-subduction zone(SSZ) ophiolites and mantle-wedge-type(MWT) orogenic peridotites. We also provide the relevant key scientific questions that need be solved in the future. The mantle sections of SSZ ophiolites and MWT orogenic peridotites represent the mantle fragments from oceanic and continental lithosphere in subduction zones, respectively. They are essential targets to study the crust-mantle interaction in subduction zones. The nature of this interaction is the complex chemical exchanges between the subducting slab and the mantle wedge under the major control of physical processes. The SSZ ophiolites can record melt/fluid-rock interaction, metamorphism,deformation, concentration of metallogenic elements and material exchange between crust and mantle, during the stages from the generation of oceanic lithosphere at spreading centers to the initiation, development, maturation and ending of oceanic subduction at continental margins. The MWT orogenic peridotites reveal the history of strong metamorphism and deformation during subduction, the multiple melt/fluid metasomatism(including silicatic melts, carbonatitic melts and silicate-bearing C-HO fluids/supercritical fluids), and the complex cycling of crust-mantle materials, during the subduction/collision and exhumation of continental plates. In order to further reveal the crust-mantle interaction using subduction-zone peridotites, it is necessary to utilize high-spatial-resolution and high-precision techniques to constrain the complex chemical metasomatism, metamorphism,deformation at micro scales, and to reveal their connections with spatial-temporal evolution in macro-scale tectonics.

Interaction between subducted continental crust and the mantle——Ⅰ. Major and trace element geochemistry of the syncollisional mafic-ultramafic intrusions in the Dabie Mountains

The syncollisional mafic\|ultramafic intrusions in the North Dabie terrane are characterized by enriched LREE, Rb, Ba, and depletion of high field strength elements, such as Nb, Zr, Ti. The high Ti/Zr and Ti/Y ratios of their parent magma suggest that crust contamination of magma is not important to the above trace elements characters. They mainly reflect the features of their mantle source which has been modified by metasomatism in subduction environment.

He-Ar isotope geochemistry of the Yaoling-Meiziwo tungsten deposit,North Guangdong Province:Constraints on Yanshanian crust-mantle interaction and metallogenesis in SE China

Isotopic abundances and ratios of He and Ar found in inclusion fluids in pyrites formed in the Yaoling-Meiziwo tungsten miner-alization epoch show that the concentration of 4He varies widely,from 1.54×10-7 cm3 STP/g to 2609×10-7 cm3 STP/g.3He is 0.759×10-12 cm3 STP/g-3.463×10-12 cm3 STP/g.3He/4He is 0.0043-4.362 Ra,varying from crustal to mantle values.The concen-tration of 40Ar ranges from 0.624×10-7 cm3 STP/g to 8.89×10-7 cm3 STP/g.The 40Ar/36Ar varies extensively,from 330 to 2952,between atmospheric and crustal or mantle radiogenic values.Mantle-derived He is present in ore-forming fluids and the calcu-lated average proportion of the mantle He is 22%;the maximum is 67%.Our research results show that mantle-derived fluids play a significant role in tungsten mineralization.The fractionation of He and Ar indicate that there was 4He-enriched air-saturated water(MSAW) in the ore-forming fluid.The ore-forming fluid was a mixture of mantle fluid,crustal magmatic fluid and MSAW.The occurrence of a mantle component in ore-forming fluid indicates the large-scale W and Sn mineralization,including Yaol-ing-Meiziwo,in southeastern China was the result of crust and mantle interaction.The underplating or intrusion of voluminous basaltic magma formed by partial melting of the upper mantle provided the necessary heat to cause partial melting of the crust and the generation of voluminous S-type granitic magmas.Crustal magmatic fluid and mantle fluid with high 3He/4He were released from magma crystallization and fractionation,mixed with the circulating modified air-saturated water,and filled the extensional tectonic fractures,leading to the formation of world-class W and Sn deposits in southeastern China.

Late Mesozoic crust-mantle interaction in southeastern Fujian——Isotopic evidence from the Pingtan igneous complex

UNDERPLATING Of mantle-derived basaltic magma and interacting with the lower crust materials are believed to be an important mechanism for the growth and transformation of the crust.

Post-Entrainment Mineral-Magma Interaction in Mantle Xenoliths from Inner Mongolia,Western North China Craton

In order to distinguish the primary microstructures developed under mantle conditions from the secondary phenomena after xenolith entrainment in the host magma, this study intends to discuss the genesis of spongy, sieve-textured, and reaction rims on mineral grains of mantle xenoliths in the Cenozoic basalts from the western North China craton. The spongy rims on primary clinopyroxene show neither obvious compositional zoning nor preferential development towards the host basalt and probably suggest an origin via partial melting within the lithospheric mantle or pressure release as the xenoliths were carried upwards. The sieve-textured rims on primary spinel show clear chemical zoning with increasing Cr# and decreasing AI towards the host basalt. They are interpreted as the result of partial melting due to heating of the host basaltic magma and decreasing pressure during ascent proc- ess. Post-entrainment reaction mainly generated secondary minerals at contacts between the host ba- saltic melt and xenoliths. The secondary clinopyroxene in reaction rims develops on primary clinopy- roxene and has higher Ti, Ca, and Fe contents and lower Mg# and Si contents than primary one, while the secondary spinel on primary Cr-AI spinel is titanomagnetite. The secondary olivine and clinopy- roxene in the reaction rims on primary orthopyroxene are enriched in Fe, Al, and Ti. The occurrence of reaction rims in mantle xenoliths reflects disequilibrium processes after xenolith entrainment in the basaltic melt. The spongy rims on primary clinopyroxene may not be related to the interaction with thehost basaltic melt, while the sieve-textured rims on primary spinel and reactions rims on primary clinopyroxene, spinel, and orthopyroxene may result from post-entrainment reaction between the host basaltic melt and xenolith minerals.

Peridotite-melt interaction:A key point for the destruction of cratonic lithospheric mantle

This paper presents an overview of recent studies dealing with different ages of mantle peridotitic xenoliths and xenocrysts from the North China Craton, with aim to provide new ideas for further study on the destruction of the North China Craton. Re-Os isotopic studies suggest that the lithospheric mantle of the North China Craton is of Archean age prior to its thinning. The key reason why such a low density and highly refractory Archean lithospheric mantle would be thinned is changes in composition, thermal regime, and physical properties of the lithospheric mantle due to interaction of peridotites with melts of different origins. Inward subduction of circum craton plates and collision with the North China Craton provided not only the driving force for the destruction of the craton, but also continuous melts derived from partial melting of subducted continental or oceanic crustal materials that resulted in the compositional change of the lithospheric mantle. Regional thermal anomaly at ca. 120 Ma led to the melting of highly modified lithospheric mantle. At the same time or subsequently lithospheric exten- sion and asthenospheric upwelling further reinforced the melting and thinning of the lithospheric mantle. Therefore, the destruction and thinning of the North China Craton is a combined result of peridotite-melt interaction (addition of volatile), enhanced regional thermal anomaly (temperature increase) and lithospheric extension (decompression). Such a complex geological process finally produced a "mixed" lithospheric mantle of highly chemical heterogeneity during the Mesozoic and Cenozoic. It also resulted in significant difference in the composition of mantle peridotitic xenoliths between different regions and times.