The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to d...The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.展开更多
The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Du...The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.展开更多
The field and microstructural features coupled with mineral chemical data from microgranular enclave(ME)and host Mesoproterozoic Kanigiri granite(KG)pluton of Nellore Schist Belt(NSB),Southeastern India,have been docu...The field and microstructural features coupled with mineral chemical data from microgranular enclave(ME)and host Mesoproterozoic Kanigiri granite(KG)pluton of Nellore Schist Belt(NSB),Southeastern India,have been documented in order to infer the likely processes responsible for the origin and evolution of ME and host KG magma.The ME and host KG bear the same mineral assemblages barring the KG which does not contain amphibole;however,they are modally disequilibrated.The ME in KG is originated due to multiple intrusions of ME magmas into the crystallizing host KG magma chamber.Field and textural features indicate the dynamic magma flow,mingling,and undercooling of the ME against a relatively cooler surface of host KG magma.The presence of NSB country rock xenoliths and its diffuse boundaries suggest the intrusive relation and marginal assimilation by the intruding KG magma.The occasional cumulate texture in the ME appears to have formed by the accumulation of early-formed minerals that crystallized rapidly in the ME magma globules.The ME shows the magmatically deform features developed due to the flowage and erosion by the subsequent intrusions of ME magma pulses into the crystallizing host KG magma chamber.The ME amphiboles show unusual composition as ferro-edenitic hornblende to potassian-hastingsitic hornblende,that crystallized in the subalkaline-alkaline transition,low fO_(2)(reducing to mildly oxidizing)magma.The unusual extremely low Mg/Mg+Fe^(t)=0.015(avg.)of ME amphiboles may be related to the changing physico-chemical(P,T,fO_(2),and H_(2)O)condition of the ME magma or they might have crystallized in equilibrium with more evolved KG magma.The KG(FeOt/MgO=37.04,avg.)and ME(FeO~t/MgO=77.72,avg.)biotites are siderophyllite,and buffered between QFM and NNO syn-crystallizing in the water undersaturated(H_(2O)≈3.58 wt.%in KG;≈3.53wt.%in ME),alkaline anorogenic(A-type)host magmas that were emplaced at mid-crustal(4–5 kbar;17 km)depth.Field,microtextural and mineral chemical evidences suggest that the alkaline KG magma originated from crustal source and evolved through synchronous fractionation,mixing,and mingling with coeval ME magmas in the KG magma chamber.展开更多
Felsic intrusions present ubiquitous structures.They result from the differential interactions between the magma components(crystal,melt,gas phase) while it flows or when the flow is perturbed by a new magma injection...Felsic intrusions present ubiquitous structures.They result from the differential interactions between the magma components(crystal,melt,gas phase) while it flows or when the flow is perturbed by a new magma injection.The most obvious structure consists in fabrics caused by the interactions of rotating grains in a flowing viscous melt.New magma inputs through dikes affect the buk massif flow,considered as global within each mineral facies.A review of the deformation and flow types developing in a magma chamber identifis the patterns that could be expected.It determines their controlling parameters and summarizes the tools for their quantification.Similarly,a brief review of the theology of a complex multiphase magma identifies and suggests interactions between the different components.The specific responses each component presents lead to instability development.In particular,the change in vorticity orientation,associated with the switch between monoclinic to triclinic flow is a cause of many instabilities.Those are preferentially local.Illustrations include fabric development,shear zones and flow banding.They depend of the underlying rheology of interacting magmas.Dikes,enclaves,schlieren and ladder dikes result from the interactions between the magma components and changing boundary conditions.Orbicules,pegmatites,unidirectional solidification textures and miarolitic cavities result from the interaction of the melt with a gaseous phase.The illustrations examine what is relevant to the bulk flow,local structures or boundary conditions.In each case a field observation illustrates the instability.The discussion reformulates instability observations,suggesting new trails for ther description and interpretation in terms of local departure to a bulk flow.A brief look at larger structures and at their evolution tries to relate these instabilities on a broader scale.The helical structures of the Ricany pluton,Czech Republic and by the multiple granitic intrusions of Dolbel,Niger illustrate such events.展开更多
The East Kunlun Orogenic Belt(EKOB)in northeast margin of the Qinghai-Tibetan Plateau is an important part of the Central Orogenic System(COS).During the long-time geological evolution,complicated tectono
Plagioclase phenocrysts from mafic enclaves and plagioclase from its host granite possess a pat-tem of complex zonation. A plagioclase phenocryst can generally be divided into three parts : an oscillatory, locally pat...Plagioclase phenocrysts from mafic enclaves and plagioclase from its host granite possess a pat-tem of complex zonation. A plagioclase phenocryst can generally be divided into three parts : an oscillatory, locally patchy zoned core (An47-19), a ring with dusty, more calcic plagioclase (An64-20) and a normally zoned rim composed of sodic plagioclase (An22-3. 3). Majordiscontinuities in zoning coincide with resorption suffeces that are overgrown by the more calcic plagioclase. The cores of large plagioclase phenocrysts from mafic enclaves and host granite show similar zoning patterns and similar compositions, indicating their crystallization under the same conditions . Steep normal zoning of the rims of plagioclases both from host granite and mafic enclaves illustrates a drastic decrease in An content which is considered to have resulted from the continuous differentiation of hybrid magma and efficient heat loss because of the upward emplacement of the residual magma. Wide rims of plagioclases from the host granite against thc discrete rims of plagioclases from mafic enclaves indicate that differentiation and cooling lasted much longer in the host granite than in the mafic enclaves.展开更多
Li-F granites all over the world can be represented by three end members, i. e., theNa-rich ongonite (O), the K-rich xianghualingite (X) and the Si-rich topazite (T). Charac-ters and criteria are presented for these e...Li-F granites all over the world can be represented by three end members, i. e., theNa-rich ongonite (O), the K-rich xianghualingite (X) and the Si-rich topazite (T). Charac-ters and criteria are presented for these end-member rocks. Vertical zoning in Li-F granites, asreflected by increasing normative Q and C (corundum) and decreasing ALK (K2O + Na2O)with increasing content of fluorine, can be explained using the three-end-member scheme interms of petrochemistry and norms. Considering the difference in melt structure, viscosity anddensity between the end members, in couple with the reguarities that govern the Na-K and Si-ALK segregation known from field evidence and experiments, it is suggested that the three endmembers may have resulted from liquid segregation (immiscibility) rather than from crystalfractionation as commonly believed.展开更多
Limu granite massif is a rather typical Mesozoic rare-metal granite in South China . Studying Limu granite massif has important petrological significance for understanding the genesis of rare-metal granites .This pape...Limu granite massif is a rather typical Mesozoic rare-metal granite in South China . Studying Limu granite massif has important petrological significance for understanding the genesis of rare-metal granites .This paper deals with the typical petrographic characteristics and peculiarity of REE in massif , and discusses the genesis of Limu granite massif in terms of analysis of these characteristics . It is suggested that Limu granite massif is derivative product of a high ordered superimposed -remelting granitic magma .展开更多
The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary envi...The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary environment;nature and its tectonic evolution history and tectonic domain and Gut Tis relationship;therefore,the research on Chang Ning Menglian zone have a great significance to solve many problems of the Sanjiang fold belt in Tethys and Himalaya tectonic area.'Hot spring'is located in the west margin of the southern Changning Menglian belt,studying Yunnan Fengqing hot spring group'geological and petrology characteristics roundly and in depth,concluding the metamorphism and deformation characteristics,clarifying the metamorphism effect and its stages,understanding the association its combination with the Changning Menglian belt between,therefore it has the great significance to solve the geological evolution history in the Sanjiang area,especially the paleo Tethyan tectonic belt,as well as Gondwana and Eurasia boundaries and other major problem.Through collect and read the literature data,measurement of field section,geological investigation,research and Study on rock sheet indoor,rock composition test,electron probe testing system,summarize the geological characteristics and petrological characteristics of'hot springs group',and through the discussion of the geochemical characteristics of rocks,explore its rock assemblages,characteristics of original rock and analysis of metamorphism and deformation stages,to provide basic data for regional geological evolution.The study shows that the main lithology is biotite quartz schist,mica schist and epimetamorphic sandstone interspersed with a small amount of phyllonite,granulite,silicalite,carbonaceous slate and phyllitic cataclasite that contains some pressure breccia.The metamorphic mineral paragenetic assemblage of the representative rock is:M1 biotite(Bi)+plagioclase(Pl)+quartz(Q),and M2 muscovite(Mus)+quartz(Q).The protolith is felsic rock and sedimentary rock that belongs to argiloid.On the basis of comparison,the stratigraphic sequence of the protolith is consistent with the type section of Wenquan formation.Along with the subduction(Hercynian)-subduction(Indosinian)-orogenic(Yanshan Himalayan period)process of Changning Menglian belt,hot springs group experienced two stages of metamorphism and three stages of deformation,metamorphic temperature at400-500℃,the pressure is foucs on 0.3-0.62Gpa,and shown the retrograde metamorphism of the low greenschist facies.Geological age of hot springs formation is early Devonian(survey team of Yunnan District three units,1980),sedimentary environment is mainly shallow and semi deep sea,observed Bouma sequence in rock slice,therefore,the depositional environment may be fan or basin of sea,the sedimentary formations are mainly clastic rocksiliceous rock formation,the upper coal—contained formation.With the Changning Meng Lian ocean expansion,ocean island begin to develop,material deposition continuing,appearing volcano material,the protolith may contain volcano matter through studying the thin section.To the Late Permian,Crust of Changning Menglian ocean begin to subduct to the east of the Yangtze block,ocean basin began to close,but it still has formation here at this time,mainly shallow carbonate formation,with proceeding of subduction,in the low temperature groove(7Km deep),due to changes in temperature and pressurer,appearing metamorphism(M1)and deformation(D1)for the first time,the shear effect produced by deformation lead to some cleavage,occurring regional foliation S1,major metamorphic minerals formed in metamorphism is long flake biotite.The main metamorphic mineral assemblages are biotite(Bi)+feldspar(Pl)+quartz(Q).Subsequently,crustal uplift,depositional break,because the Changning Meng Lianyang has closed during the Indosinian period,Baoshan-Zhenkang block in the west and the Yangtze block in the east knocked each other.In the Indosinian,under the action of faults,the hot spring formation clipping and retracing,back to a position about1-2Km depth,the position is still belongs to the low temperature groove,and occurring axial cleavage in the core of the fold,namely S2.That is,the emergence of the second metamorphism(M2)and deformation(D2).The deformation is affected by the strong pressure,so the rock have dewatered,so the second metamorphic deformation process is affected by temperature(T),pressure(Ps)and fluid(C).The main metamorphic minerals in the second generation of metamorphism is Muscovite,while there have some of biotite formed in same period,find that the first phase of biotite parallel growth of rock slice,namely S1 parallel S2,and we can see incomplete metamorphism biotite,so the the Muscovite is formed by the first stage of metamorphism and metamorphic biotite.The main mineral of the second stage metamorphism is Muscovite(Mus)+quartz(Q) Then,the crust continues to rise,the sedimentary break continues.In the Jurassic Cretaceous start orogeny,namely Yanshan period intracontinental orogeny,occurred third deformation(D3),under extrusion shearing,S3 emergencing,after Yanshan intracontinental orogenic period,in Himalayan period there have large-scale nappe structure and differential uplift and faulting.So the third deformation(D3)strengthened,with weak metamorphism,sericite emergencing.展开更多
The authors studied geochronology and geochemical data of the Songjianghe biotite monzogranite in the southern Zhangguangcai Range in order to determine its formation age,magma source,and tectonic environment. The res...The authors studied geochronology and geochemical data of the Songjianghe biotite monzogranite in the southern Zhangguangcai Range in order to determine its formation age,magma source,and tectonic environment. The results indicate that the Songjianghe biotite monzogranite was formed in the Middle Jurassic with an age of 168. 2 ± 2. 0 Ma( MSWD = 0. 93). The monzogranite was characterized by high alkali and low Ca O and Mg O,belonging to high-potassium calc-alkaline,metaluminous I-type granite. The rock is enriched in large ion lithophile elements such as Rb,Ba,and K and strongly depleted high field strength elements such as P,Ti,Nb,and Ta. It is concluded that the Songjianghe biotite monzogranite was derived from partial melting of amphibolite facies metamorphism mafic lower-crust and its formation was controlled by the Pacific Plate subduction.展开更多
There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit...There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.展开更多
Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdise giant magmatic belt, within which the Qüxü batholith is the most typical MME-bearing pluton. Systematic sampl...Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdise giant magmatic belt, within which the Qüxü batholith is the most typical MME-bearing pluton. Systematic sampling for granodioritic host rock, mafic microgranular enclaves and gabbro nearby at two locations in the Qüxü batholith, and subsequent zircon SHRIMP II U-Pb dating have been conducted. Two sets of isotopic ages for granodioritic host rock, mafic microgranular enclaves and gabbro are 50.4±1.3 Ma, 51.2±1.1 Ma, 47.0±l Ma and 49.3±1.7 Ma, 48.9±1.1 Ma, 49.9±1.7 Ma, respectively. It thus rules out the possibilities of mafic microgranular enclaves being refractory residues after partial melting of magma source region, or being xenoliths of country rocks or later intrusions.Therefore, it is believed that the three types of rocks mentioned above likely formed in the same magmatic event, i.e., they formed by magma mixing in the Eocene (c. 50 Ma). Compositionally, granitoid host rocks incline towards acidic end member involved in magma mixing, gabbros are akin to basic end member and mafic microgranular enclaves are the incompletely mixed basic magma clots trapped in acidic magma. The isotopic dating also suggested that huge-scale magma mixing in the Gangdise belt took place 15-20 million years after the initiation of the India-Asia continental collision, genetically related to the underplating of subduction-collision-induced basic magma at the base of the continental crust. Underplating and magma mixing were likely the main process of mass-energy exchange between the mantle and the crust during the continental collision, and greatly contributed to the accretion of the continental crust, the evolution of the lithosphere and related mineralization beneath the portion of the Tibetan Plateau to the north of the collision zone.展开更多
Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yul...Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yulong porphyry copper belt can reveal the tectono-magmatic processes in the Sanjiang region.In this study,we present new zircon U-Pb-Hf isotopes and whole rock geochemistry of Cenozoic granitoids from the Zhalaga area in the northern Yulong porphyry copper belt.The Zircon U-Pb dating results show that the Zhalaga granitic porphyry crystallized at ca.42-38 Ma.These porphyry deposits are depleted in Nb,Ta,Sr,and Ti enriched in alkaline and rare earth elements(REEs),and exhibit high zircon saturation temperatures,that strongly indicate A-type affinity.These data and the generally positiveεHf(t)values(2.0-4.5)suggest the magmas originated from a hybrid of partial melting of subduction-modified lithospheric mantle,possibly triggered by upwelling of the asthenospheric mantle.Geochronological and geochemical data of the current and previous studies distinguish three magmatic phases during the Cenozoic in the Jinshajiang-Ailaoshan region:(1)ca.62-48 Ma;(2)ca.44-30 Ma;and(3)ca.28-16 Ma.The strong collision between the Indian and Eurasian plates produced relatively fast convergence rates during the first episode(ca.62-48 Ma),whereas the subsequent right-lateral strike-slip faulting in the Jinshajiang fault zone initiated at ca.43 Ma is associated with the relatively low India-Eurasia convergence rates during ca.44-30 Ma.These significantly impacted the nature and spatial distribution of the magmatism and the large-scale metallogeny during the Cenozoic in the Sanjiang region.We suggest that the Zhalaga alkali-rich magmas occurred in a transition period from involving soft to hard collisional settings.This remarkable example demonstrates that alkali-rich magmas with A-type affinity are also generated in an orogenic tectonic setting.展开更多
文摘The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.
基金supported by Special Fund for Basic Scientific Research of Central Colleges,Chang’an University(Grant No.:300102279210)the Natural Science Foundation of Shaanxi Province(Grant No.:2019JQ-690)the geological and mineral survey evaluation project of China Geological Survey(Grant No.:DD20190065).
文摘The Dunde iron-zinc polymetallic deposit is one of large iron deposits occurred in the Awulale Metallogenetic Belt,Western Tianshan(NW-China).This study reports new geochronology and geochemistry for granite in the Dunde mining area in order to constrain the tectonicmagmatic activities and metallogenesis of this region.Granites in the southwest of Dunde mining area are mainly syenogranites intruded into volcanics of the Dahalajunshan Formation in the Early Carboniferous,and they are far from the area where ore bodies and mineralized altered rocks are widely developed.LA-ICP-MS U–Pb zircon dating indicates that Dunde syenogranite was at 306.8±1.0 Ma,which could constrain the upper limit of metallogenic age for this deposit.The Dunde granites are high SiO_(2)(73.41–80.07 wt%),high differentiation index(D.I.=89.7–95.0),weakly peraluminous to metaluminous(A/CNK=0.94–1.08),and they are enriched in LILE and LREE and depleted in Eu,Ba,Sr and P_(2)O_(5),indicating that they belong to highly fractionated Ⅰ-type granite.Based on εHf values(+9.2 to+10.5)for zircon and high εNd(-t)values(+4.7 to+5.8)for whole-rock,and the two-stage model ages for 601–735 Ma,suggest that the magma source could be the juvenile lower crust.Combined with regional geological setting,the 306.8 Ma Dunde granites are formed in post-collision extensional tectonic setting.
基金UGC-Dr.D.S.Kothari Postdoctoral FellowshipNo.F.4-2/2006(BSR)/ES/20-21/0005supported under a research grant[Mo ES/P.O.(Geo)/101(v)/2017]to SK。
文摘The field and microstructural features coupled with mineral chemical data from microgranular enclave(ME)and host Mesoproterozoic Kanigiri granite(KG)pluton of Nellore Schist Belt(NSB),Southeastern India,have been documented in order to infer the likely processes responsible for the origin and evolution of ME and host KG magma.The ME and host KG bear the same mineral assemblages barring the KG which does not contain amphibole;however,they are modally disequilibrated.The ME in KG is originated due to multiple intrusions of ME magmas into the crystallizing host KG magma chamber.Field and textural features indicate the dynamic magma flow,mingling,and undercooling of the ME against a relatively cooler surface of host KG magma.The presence of NSB country rock xenoliths and its diffuse boundaries suggest the intrusive relation and marginal assimilation by the intruding KG magma.The occasional cumulate texture in the ME appears to have formed by the accumulation of early-formed minerals that crystallized rapidly in the ME magma globules.The ME shows the magmatically deform features developed due to the flowage and erosion by the subsequent intrusions of ME magma pulses into the crystallizing host KG magma chamber.The ME amphiboles show unusual composition as ferro-edenitic hornblende to potassian-hastingsitic hornblende,that crystallized in the subalkaline-alkaline transition,low fO_(2)(reducing to mildly oxidizing)magma.The unusual extremely low Mg/Mg+Fe^(t)=0.015(avg.)of ME amphiboles may be related to the changing physico-chemical(P,T,fO_(2),and H_(2)O)condition of the ME magma or they might have crystallized in equilibrium with more evolved KG magma.The KG(FeOt/MgO=37.04,avg.)and ME(FeO~t/MgO=77.72,avg.)biotites are siderophyllite,and buffered between QFM and NNO syn-crystallizing in the water undersaturated(H_(2O)≈3.58 wt.%in KG;≈3.53wt.%in ME),alkaline anorogenic(A-type)host magmas that were emplaced at mid-crustal(4–5 kbar;17 km)depth.Field,microtextural and mineral chemical evidences suggest that the alkaline KG magma originated from crustal source and evolved through synchronous fractionation,mixing,and mingling with coeval ME magmas in the KG magma chamber.
文摘Felsic intrusions present ubiquitous structures.They result from the differential interactions between the magma components(crystal,melt,gas phase) while it flows or when the flow is perturbed by a new magma injection.The most obvious structure consists in fabrics caused by the interactions of rotating grains in a flowing viscous melt.New magma inputs through dikes affect the buk massif flow,considered as global within each mineral facies.A review of the deformation and flow types developing in a magma chamber identifis the patterns that could be expected.It determines their controlling parameters and summarizes the tools for their quantification.Similarly,a brief review of the theology of a complex multiphase magma identifies and suggests interactions between the different components.The specific responses each component presents lead to instability development.In particular,the change in vorticity orientation,associated with the switch between monoclinic to triclinic flow is a cause of many instabilities.Those are preferentially local.Illustrations include fabric development,shear zones and flow banding.They depend of the underlying rheology of interacting magmas.Dikes,enclaves,schlieren and ladder dikes result from the interactions between the magma components and changing boundary conditions.Orbicules,pegmatites,unidirectional solidification textures and miarolitic cavities result from the interaction of the melt with a gaseous phase.The illustrations examine what is relevant to the bulk flow,local structures or boundary conditions.In each case a field observation illustrates the instability.The discussion reformulates instability observations,suggesting new trails for ther description and interpretation in terms of local departure to a bulk flow.A brief look at larger structures and at their evolution tries to relate these instabilities on a broader scale.The helical structures of the Ricany pluton,Czech Republic and by the multiple granitic intrusions of Dolbel,Niger illustrate such events.
基金supported by the National Science Foundation of China (Grant No., 41472191, 41502191, 41172186, 40972136)the Special Fund for Basic Scientific Research of Central Colleages, Chang’an University (Grant Nos. 310827161002, 310827161006)+1 种基金the Commonweal Geological Surveythe Aluminum Corporation of China and the Land-Resources Department of Qinghai Province (Grant No., 200801)
文摘The East Kunlun Orogenic Belt(EKOB)in northeast margin of the Qinghai-Tibetan Plateau is an important part of the Central Orogenic System(COS).During the long-time geological evolution,complicated tectono
文摘Plagioclase phenocrysts from mafic enclaves and plagioclase from its host granite possess a pat-tem of complex zonation. A plagioclase phenocryst can generally be divided into three parts : an oscillatory, locally patchy zoned core (An47-19), a ring with dusty, more calcic plagioclase (An64-20) and a normally zoned rim composed of sodic plagioclase (An22-3. 3). Majordiscontinuities in zoning coincide with resorption suffeces that are overgrown by the more calcic plagioclase. The cores of large plagioclase phenocrysts from mafic enclaves and host granite show similar zoning patterns and similar compositions, indicating their crystallization under the same conditions . Steep normal zoning of the rims of plagioclases both from host granite and mafic enclaves illustrates a drastic decrease in An content which is considered to have resulted from the continuous differentiation of hybrid magma and efficient heat loss because of the upward emplacement of the residual magma. Wide rims of plagioclases from the host granite against thc discrete rims of plagioclases from mafic enclaves indicate that differentiation and cooling lasted much longer in the host granite than in the mafic enclaves.
文摘Li-F granites all over the world can be represented by three end members, i. e., theNa-rich ongonite (O), the K-rich xianghualingite (X) and the Si-rich topazite (T). Charac-ters and criteria are presented for these end-member rocks. Vertical zoning in Li-F granites, asreflected by increasing normative Q and C (corundum) and decreasing ALK (K2O + Na2O)with increasing content of fluorine, can be explained using the three-end-member scheme interms of petrochemistry and norms. Considering the difference in melt structure, viscosity anddensity between the end members, in couple with the reguarities that govern the Na-K and Si-ALK segregation known from field evidence and experiments, it is suggested that the three endmembers may have resulted from liquid segregation (immiscibility) rather than from crystalfractionation as commonly believed.
文摘Limu granite massif is a rather typical Mesozoic rare-metal granite in South China . Studying Limu granite massif has important petrological significance for understanding the genesis of rare-metal granites .This paper deals with the typical petrographic characteristics and peculiarity of REE in massif , and discusses the genesis of Limu granite massif in terms of analysis of these characteristics . It is suggested that Limu granite massif is derivative product of a high ordered superimposed -remelting granitic magma .
文摘The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary environment;nature and its tectonic evolution history and tectonic domain and Gut Tis relationship;therefore,the research on Chang Ning Menglian zone have a great significance to solve many problems of the Sanjiang fold belt in Tethys and Himalaya tectonic area.'Hot spring'is located in the west margin of the southern Changning Menglian belt,studying Yunnan Fengqing hot spring group'geological and petrology characteristics roundly and in depth,concluding the metamorphism and deformation characteristics,clarifying the metamorphism effect and its stages,understanding the association its combination with the Changning Menglian belt between,therefore it has the great significance to solve the geological evolution history in the Sanjiang area,especially the paleo Tethyan tectonic belt,as well as Gondwana and Eurasia boundaries and other major problem.Through collect and read the literature data,measurement of field section,geological investigation,research and Study on rock sheet indoor,rock composition test,electron probe testing system,summarize the geological characteristics and petrological characteristics of'hot springs group',and through the discussion of the geochemical characteristics of rocks,explore its rock assemblages,characteristics of original rock and analysis of metamorphism and deformation stages,to provide basic data for regional geological evolution.The study shows that the main lithology is biotite quartz schist,mica schist and epimetamorphic sandstone interspersed with a small amount of phyllonite,granulite,silicalite,carbonaceous slate and phyllitic cataclasite that contains some pressure breccia.The metamorphic mineral paragenetic assemblage of the representative rock is:M1 biotite(Bi)+plagioclase(Pl)+quartz(Q),and M2 muscovite(Mus)+quartz(Q).The protolith is felsic rock and sedimentary rock that belongs to argiloid.On the basis of comparison,the stratigraphic sequence of the protolith is consistent with the type section of Wenquan formation.Along with the subduction(Hercynian)-subduction(Indosinian)-orogenic(Yanshan Himalayan period)process of Changning Menglian belt,hot springs group experienced two stages of metamorphism and three stages of deformation,metamorphic temperature at400-500℃,the pressure is foucs on 0.3-0.62Gpa,and shown the retrograde metamorphism of the low greenschist facies.Geological age of hot springs formation is early Devonian(survey team of Yunnan District three units,1980),sedimentary environment is mainly shallow and semi deep sea,observed Bouma sequence in rock slice,therefore,the depositional environment may be fan or basin of sea,the sedimentary formations are mainly clastic rocksiliceous rock formation,the upper coal—contained formation.With the Changning Meng Lian ocean expansion,ocean island begin to develop,material deposition continuing,appearing volcano material,the protolith may contain volcano matter through studying the thin section.To the Late Permian,Crust of Changning Menglian ocean begin to subduct to the east of the Yangtze block,ocean basin began to close,but it still has formation here at this time,mainly shallow carbonate formation,with proceeding of subduction,in the low temperature groove(7Km deep),due to changes in temperature and pressurer,appearing metamorphism(M1)and deformation(D1)for the first time,the shear effect produced by deformation lead to some cleavage,occurring regional foliation S1,major metamorphic minerals formed in metamorphism is long flake biotite.The main metamorphic mineral assemblages are biotite(Bi)+feldspar(Pl)+quartz(Q).Subsequently,crustal uplift,depositional break,because the Changning Meng Lianyang has closed during the Indosinian period,Baoshan-Zhenkang block in the west and the Yangtze block in the east knocked each other.In the Indosinian,under the action of faults,the hot spring formation clipping and retracing,back to a position about1-2Km depth,the position is still belongs to the low temperature groove,and occurring axial cleavage in the core of the fold,namely S2.That is,the emergence of the second metamorphism(M2)and deformation(D2).The deformation is affected by the strong pressure,so the rock have dewatered,so the second metamorphic deformation process is affected by temperature(T),pressure(Ps)and fluid(C).The main metamorphic minerals in the second generation of metamorphism is Muscovite,while there have some of biotite formed in same period,find that the first phase of biotite parallel growth of rock slice,namely S1 parallel S2,and we can see incomplete metamorphism biotite,so the the Muscovite is formed by the first stage of metamorphism and metamorphic biotite.The main mineral of the second stage metamorphism is Muscovite(Mus)+quartz(Q) Then,the crust continues to rise,the sedimentary break continues.In the Jurassic Cretaceous start orogeny,namely Yanshan period intracontinental orogeny,occurred third deformation(D3),under extrusion shearing,S3 emergencing,after Yanshan intracontinental orogenic period,in Himalayan period there have large-scale nappe structure and differential uplift and faulting.So the third deformation(D3)strengthened,with weak metamorphism,sericite emergencing.
基金project of National Natural Science Foundation of China(No.41272095)
文摘The authors studied geochronology and geochemical data of the Songjianghe biotite monzogranite in the southern Zhangguangcai Range in order to determine its formation age,magma source,and tectonic environment. The results indicate that the Songjianghe biotite monzogranite was formed in the Middle Jurassic with an age of 168. 2 ± 2. 0 Ma( MSWD = 0. 93). The monzogranite was characterized by high alkali and low Ca O and Mg O,belonging to high-potassium calc-alkaline,metaluminous I-type granite. The rock is enriched in large ion lithophile elements such as Rb,Ba,and K and strongly depleted high field strength elements such as P,Ti,Nb,and Ta. It is concluded that the Songjianghe biotite monzogranite was derived from partial melting of amphibolite facies metamorphism mafic lower-crust and its formation was controlled by the Pacific Plate subduction.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.92162210,42172096 and 41773028).
文摘There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.
基金the grants of the National Key Project for Basic Research of China(No.2002CB412600)the National Natural Science Foundation of China(Nos.40172025,40103003,49802005,49772107,40473020)the key project on the Tibetan Plateau of the Ministryof Land and Resources of China(No.20010102401).
文摘Abundant mafic microgranular enclaves (MMEs) extensively distribute in granitoids in the Gangdise giant magmatic belt, within which the Qüxü batholith is the most typical MME-bearing pluton. Systematic sampling for granodioritic host rock, mafic microgranular enclaves and gabbro nearby at two locations in the Qüxü batholith, and subsequent zircon SHRIMP II U-Pb dating have been conducted. Two sets of isotopic ages for granodioritic host rock, mafic microgranular enclaves and gabbro are 50.4±1.3 Ma, 51.2±1.1 Ma, 47.0±l Ma and 49.3±1.7 Ma, 48.9±1.1 Ma, 49.9±1.7 Ma, respectively. It thus rules out the possibilities of mafic microgranular enclaves being refractory residues after partial melting of magma source region, or being xenoliths of country rocks or later intrusions.Therefore, it is believed that the three types of rocks mentioned above likely formed in the same magmatic event, i.e., they formed by magma mixing in the Eocene (c. 50 Ma). Compositionally, granitoid host rocks incline towards acidic end member involved in magma mixing, gabbros are akin to basic end member and mafic microgranular enclaves are the incompletely mixed basic magma clots trapped in acidic magma. The isotopic dating also suggested that huge-scale magma mixing in the Gangdise belt took place 15-20 million years after the initiation of the India-Asia continental collision, genetically related to the underplating of subduction-collision-induced basic magma at the base of the continental crust. Underplating and magma mixing were likely the main process of mass-energy exchange between the mantle and the crust during the continental collision, and greatly contributed to the accretion of the continental crust, the evolution of the lithosphere and related mineralization beneath the portion of the Tibetan Plateau to the north of the collision zone.
基金supported by the National Natural Science Foundation of China(No.41776056)Natural Science Foundation of Guangdong Province(Nos.2017A030310395,2018B030311030)China Postdoctoral Science Foundation(grant No.2020M672671)。
文摘Large-scale Cenozoic magmatic rocks from the interplay between the Indian and Eurasian plate are exposed in the Yulong porphyry copper belt in the northern Jinshajiang-Ailaoshan domain.Alkali-rich magmas along the Yulong porphyry copper belt can reveal the tectono-magmatic processes in the Sanjiang region.In this study,we present new zircon U-Pb-Hf isotopes and whole rock geochemistry of Cenozoic granitoids from the Zhalaga area in the northern Yulong porphyry copper belt.The Zircon U-Pb dating results show that the Zhalaga granitic porphyry crystallized at ca.42-38 Ma.These porphyry deposits are depleted in Nb,Ta,Sr,and Ti enriched in alkaline and rare earth elements(REEs),and exhibit high zircon saturation temperatures,that strongly indicate A-type affinity.These data and the generally positiveεHf(t)values(2.0-4.5)suggest the magmas originated from a hybrid of partial melting of subduction-modified lithospheric mantle,possibly triggered by upwelling of the asthenospheric mantle.Geochronological and geochemical data of the current and previous studies distinguish three magmatic phases during the Cenozoic in the Jinshajiang-Ailaoshan region:(1)ca.62-48 Ma;(2)ca.44-30 Ma;and(3)ca.28-16 Ma.The strong collision between the Indian and Eurasian plates produced relatively fast convergence rates during the first episode(ca.62-48 Ma),whereas the subsequent right-lateral strike-slip faulting in the Jinshajiang fault zone initiated at ca.43 Ma is associated with the relatively low India-Eurasia convergence rates during ca.44-30 Ma.These significantly impacted the nature and spatial distribution of the magmatism and the large-scale metallogeny during the Cenozoic in the Sanjiang region.We suggest that the Zhalaga alkali-rich magmas occurred in a transition period from involving soft to hard collisional settings.This remarkable example demonstrates that alkali-rich magmas with A-type affinity are also generated in an orogenic tectonic setting.
