Mineral Chemistry,Trace Elements,Isotopic Analysis and Zircon U-Pb Dating in the Hesar Pluton,Northern UDMA,Iran:Implications for Pre-Collisional Magma Mixing

The Hesar pluton in the northern Urumieh-Dokhtar magmatic arc hosts numerous mafic-microgranular enclaves(MMEs).Whole rock geochemistry,mineral chemistry,zircon U-Pb and Sr-Nd isotopes were measured.It is suggested that the rocks are metaluminous(A/CNK=1.32-1.45),subduction-related I-type calc-alkaline gabbro to diorite with similar mineral assemblages and geochemical signatures.The host rocks yielded an U-Pb crystallization age of 37.3±0.4 Ma for gabbro-diorite.MMEs have relatively low SiO_(2) contents(52.9-56.6 wt%)and high Mg^(#)(49.8-58.7),probably reflecting a mantle-derived origin.Chondrite-and mantle-normalized trace element patterns are characterized by LREE and LILE enrichment,HREE and HFSE depletion with slight negative Eu anomalies(Eu/Eu^(*)=0.86-1.03).The host rocks yield(^(87)Sr/^(86)Sr)_(i) ratios of 0.70492-0.70510,positive ε_(Nd)(t)values of+1.55-+2.06 and T_(DM2)of 707-736 Ma,which is consistent with the associated mafic microgranular enclaves((^(87)Sr/^(86)Sr)_(i)=0.705014,ε_(Nd)(t)=+1.75,T_(DM2)=729 Ma).All data suggest magma-mixing for enclave and host rock formation,showing a complete equilibration between mixed-mafic and felsic magmas,followed by rapid diffusion.The T_(DM1)(Nd)and T_(DM2)(Nd)model ages and U-Pb dating indicate that the host pluton was produced by partial melting of the lower continental crust and subsequent mixing with injected lithospheric mantlederived magmas in a pre-collisional setting of Arabian-Eurasian plates.Clinopyroxene composition indicates a crystallization temperature of~1000℃ and a depth of~9 km.

Source Enrichment Control on the Scale of Magmatic-Hydrothermal W-Sn Mineralization:Insights from Triassic and Jurassic Magma Reservoirs in the Continental Crust,Xitian,South China

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.

基于MAGMA的铝合金发动机缸体低压铸造工艺优化

以铝合金发动机缸体的低压铸造过程为研究对象,应用MAGMA铸造模拟软件对充型及凝固过程进行模拟,将固相分数、充型温度、虚拟实验设计以及非热平衡状态的模拟结果和实际生产情况相结合,制定工艺参数,预测缺陷产生的位置,确定最佳工艺参数组合,优化生产工艺,保证质量稳定。

Magma source and tectonic setting of the Dunde granite in the Western Tianshan:constraints from geochronology,geochemistry,and Sr–Nd–Hf isotopes

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.

Peraluminous A-type granites formed through synchronous fractionation,magma mixing,mingling,and undercooling:evidence from microgranular enclaves and host Mesoproterozoic Kanigiri granite pluton,Nellore Schist Belt,southeast India

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.

Decoding the nature of interaction between felsic clasts and mafic magma in a subvolcanic magma chamber from amphibole–titanite transformation and chemistry

The Ghansura Rhyolite Dome of Bathani vol-cano-sedimentary sequence,eastern India,represents a subvolcanic felsic magma chamber that was invaded by crystal-rich mafic magma during its cooling phase to form an assortment of hybrid rocks.A prominent solidified portion of the magma reservoir was embedded in the intruding mafic magma as fragments or clasts that pro-duced mafic rocks with felsic clasts.Two distinct compo-sitional zones could be identified in the mafic rocks containing felsic clasts-(a)medium-grained mafic zones that are dominated by amphiboles,and(b)fine-grained felsic zones consisting primarily of quartz and feldspar.Amphiboles occur in most of the felsic clasts suggesting the mechanical transfer of crystals from the mafic to the felsic zones.Compositions of amphiboles were determined from both the mafic and felsic zones that show linear compositional variation from actinolite to ferro-hornblende through magnesio-hornblende,suggesting the interplay of complex substitutions in individual amphibole sites.Cationic schemes have confirmed the role of pargasite(Pg)-type substitution,which is a combination of edenite(Ed)-and tschermakite(Ts)-type substitutions.Moreover,amphibole has been extensively replaced by titanite in the studied rock.Titanite produced in the mafic zones due to the destabilization of amphiboles was observed migrating from the mafic to the felsic zones through mineral-trans-porting veins.Compositions of titanite were determined from grains that occur in association with amphiboles and those which are present as individual entities in the felsic zones.Similar to amphiboles,titanite also displays cationic substitutions in the studied rock.From the results presented in this work,we infer that extensive replacement of amphibole by titanite and cationic substitutions in amphi-boles,and also titanite,may be considered important pet-rogenetic indicators to decipher magma mixing events.

Textural and compositional zoning in plagioclase phenocrysts:implications for magma chamber processes in the Emeishan large Igneous Province,SW China

Textural and compositional zoning within plagioclase phenocrysts records the magma chamber processes,such as magma differentiation,magma recharge and mixing,and crustal contamination.The plagioclase phenocrysts in the Daqiao and Qiaojia plagioclase-phyric basalts from the Emeishan Large Igneous Province(LIP)show complex textural and compositional zoning patterns,e.g.,normal,reverse,oscillatory,and patchy zoning patterns.Most plagioclase phenocrysts exhibit a core–rim normal zoning pattern(Pl-A)with euhedral high-An cores(An=76–78%,in mole fraction)and low-An rims(An=68–72%),indicative of the crystal regrowth processes caused by recharge of relatively evolved magmas after the formation of high-An cores.Some phenocrysts have a core–rim reverse zoning pattern(Pl-B)with irregular ovaloid cores,characterized by extremely low An(60–61 mol%)and Ba(84–88 ppm)contents and extremely high87Sr/86Sr ratios(0.7120–0.7130).The rims of the Pl-B have relatively high An(69–72%),Ba(~160 ppm)contents,and low87Sr/86Sri(~0.7056).These Pl-B plagioclase phenocrysts preserve the information about the interaction between the crustal xenocrysts and the transporting magmas.Some plagioclase phenocrysts show a core–mantle–rim oscillatory zoning pattern(Pl-C)with multiple oscillations of An(70–80%),Ba(88–147ppm)from core to rim,revealing replenishment and mixing of multiple batches of basaltic melts with diverse compositions.87Sr/86Sr ratios of the Pl-C do not vary significantly(0.7050–0.7054).A small portion of phenocrysts has patchy patterns in the cores(Pl-D),where the low-An patches(72–75%)in form of elliptical or irregular elongated shapes were enclosed by the high-An domains(80–87%).These features can be attributed to crystal dissolution and regrowth processes during the reaction between earlyformed low-Cumulates and recharged hot primitive melts.The cores,mantles,and rims of different types of plagioclase phenocrysts(except the core of Pl-B)commonly display nearly constant Sr isotopic compositions,implying insignificant wall-rock assimilation at shallow-level magma reservoir(s)during the growth of these plagioclase phenocrysts.In conclusion,the massive crystallization of plagioclase in the late stage was an important controlling factor for the formation of iron-rich basalts in the Emeishan LIP.

Magmatic Evolution of the Western Branch of the East African Rift System Melts: Evidence by Silicate Melt Inclusions, Rock Petrography and Geochemistry of the Nyiragongo 1977 and 2002 Lavas in DRC

Nyiragongo volcanic eruptions of 1977 and 2002 emitted silica-undersaturated lavas named melilite-nephelinites with microlithic to sub-porphyritic textures, and consisted of olivine, clinopyroxene (augite), phlogopite, melilite, magnetite, and rare plagioclases. This melilite-nephelinite as an evolved rock, shows low SiO2 (38.40 - 39.52 wt%) and MgO (3.10 - 4.01 wt%), and relatively high FeOt (13.76 - 14.10 wt%), Al2O3 (15.01 - 16.48 wt%), CaO (11.00 - 12.29 wt%) and Na2O + K2O (10.34 - 11.85 wt%). Unlike LA-ICP-MS on silicate melt inclusions (SMIs) hosted in augite show a pristine melt of picrobasaltic (low Ti-picrite) rock poor in SiO2 (31.14 - 32.26 wt%), FeOt (2.19 - 2.79 wt%), Al2O3 (8.01 - 9.57 wt%), and Na2O + K2O (2.34 - 3.05 wt%), while enriched in MgO (20.27 - 28.63 wt%), and CaO (24.95 - 33.17 wt%). The sums (∑REEs) for lavas and SMIs are ranging 712 - 799 and 43 - 119 ppm respectively. REE contracted multi-element patterns showed a W-feature for most lavas except for SMIs. High Rb/Sr, and low Ba/Rb, Zr/Nb, and Sm/Hf ratios of lavas suggest a phlogopite-rich source of materials. .

Contrasting oxidation states of low-Ti and high-Ti magmas control Ni-Cu sulfide and Fe-Ti oxide mineralization in Emeishan Large Igneous Province

Magmatic Ni-Cu-(PGE) sulfide and Fe-Ti oxide deposits in plume-related large igneous provinces(LIPs)are commonly related to low-Ti and high-Ti series magmas, respectively, but the major factors that control such a relationship of metallogenic types and magma compositions are unclear. Magma fOcontrols sulfur status and relative timing of Fe-Ti oxide saturation in mafic magmas, which may help clarify this issue. Taking the Emeishan LIP as a case, we calculated the magma fOof the high-Ti and low-Ti picrites based on the olivine-spinel oxygen barometer, and the partitioning of V in olivine. The obtained fOof the high-Ti series magma(FMQ + 1.1 to FMQ + 2.6) is higher than that of the low-Ti series magma(FMQ-0.5to FMQ + 0.5). The magma fOof the high-Ti and low-Ti picrites containing Fo > 90 olivine reveals that the mantle source of the high-Ti series is likely more oxidized than that of the low-Ti series. The results using the ’lambda REE’ approach show that the high-Ti series may have been derived from relatively oxidized mantle with garnet pyroxenite component. The S contents at sulfide saturation(SCSS) of the two series magmas were calculated based on liquid compositions obtained from the alpha Melts modeling, and the results show that the low-Ti series magma could easily attain the sulfide saturation as it has low fOwith S being dominantly as S. In contrast, the oxidized high-Ti series magma is difficult to attain the sulfide saturation, but could crystallize Fe-Ti oxides at magma MgO content of ~7.0 wt.%. Thus, contrasting magma fOof low-Ti and high-Ti series in plume-related LIPs may play an important role in producing two different styles of metallogeny.

液压后盖铸造工艺优化及MAGMA模拟分析

以液压后盖铸件为研究对象,材质为QT450-10。针对液压后盖铸件在实际生产中的铸造缺陷,采用MAGMA模拟软件对液压后盖生产工艺进行模拟分析,分析缺陷位置,并进行工艺优化。研究结果表明:采用顶冒口补缩方案,可以解决铸件缩松问题,有效降低铸件废品率,铸件废品率整体从8%降低为0.8%。

基于MAGMA软件的支架铸造工艺优化

以EMD大功率内燃机车支架为例,应用MAGMA模拟软件,采用温度场模拟分析和凝固补缩模拟分析,优化了铸钢件铸造工艺.根据优化后的铸造工艺方案,进行了试生产,通过解剖分析、鉴定,未发现缩孔缺陷,验证了铸造方案的可行性.采用计算机模拟浇注取代传统的试生产后验证的方法,降低了新产品的试制成本,缩短了试制周期.

基于MAGMA的球铁齿轮箱铸造工艺设计

针对球铁齿轮箱,进行了铸造工艺设计,并利用MAGMA分析软件进行了流动场、凝固场分析验证,成功地实现了该产品的批量生产,为同类产品的工艺设计提供了参考依据。

基于MAGMA的球墨铸铁铸造工艺裕度分析

基于MAGMA的模拟计算,研究40 mm×200 mm×100 mm试块在不同浇注温度、砂型刚度、孕育和石墨析出的条件下缩松行为。模拟研究表明:石墨析出率和孕育效果变化对铸件缩松形成有明显影响,浇注温度变化对铸件缩松的形成影响较小,即石墨析出和孕育方式的工艺裕度小,浇注温度的工艺裕度较大,这与试验结果基本一致;MAGMA对砂型刚度对铸件缩松形成影响的模拟结果与试验不符。

基于Magma的高压铸造模具温度场模拟分析

以汽车变速箱体零件为模型,运用Magma软件。模拟变速箱体在铸造过程中的充型流态,并对模具进行温度场模拟,分析定模、动模在喷涂前后的温度场状况。通过多组的工艺参数组合模拟,最后得到较好的模拟状态。由生产试验得知,在模具实时温度控制中,参数化调节是困难的。通过先行在Magma中模拟缩小工艺参数区间,将模拟的参数复制到压铸机上,通过微调得到理想模具温度,解决产品压铸的品质问题。能有效降低产品报废率,提高设备综合效率。

Magmatic Ni-Cu-(PGE) deposits in magma plumbing systems:Features,formation and exploration

The three most crucial factors for the formation of large and super-large magmatic sulfide deposits are： （1） a large volume of mantle-derived mafic-ultramafic magmas that participated in the formation of the deposits; （2） fractional crystallization and crustal contamination, particularly the input of sulfur from crustal rocks, resulting in sulfide immiscibility and segregation; and （3） the timing of sulfide concentration in the intrusion. The super-large magmatic Ni-Cu sulfide deposits around the world have been found in small mafic-ultramafic intrusions, except for the Sudbury deposit. Studies in the past decade indicated that the intrusions hosting large and super-large magmatic sulfide deposits occur in magma conduits, such as those in China, including Jinchuan （Gansu）, Yangliuping （Sichuan）, Kalatongke （Xinjiang）, and Hongqiling （Jilin）. Magma conduits as open magma systems provide a perfect environment for extensive concentration of immiscible sulfide melts, which have been found to occur along deep regional faults. The origin of many mantle-derived magmas is closely associated with mantle plumes, intracontinental rifts, or post-collisional extension. Although it has been confirmed that sulfide immiscibility results from crustal contamination, grades of sulfide ores are also related to the nature of the parental magmas, the ratio between silicate magma and immiscible sulfide melt, the reaction between the sulfide melts and newly injected silicate magmas, and fractionation of the sulfide melt. The field relationships of the ore-bearing intrusion and the sulfide ore body are controlled by the geological features of the wall rocks. In this paper, we attempt to demonstrate the general characteristics, formation mechanism,tectonic settings, and indicators of magmatic sulfide deposits occurring in magmatic conduits which would provide guidelines for further exploration.

Early Cretaceous Magma Mingling in Xiaocuo,Southeastern China Continental Margin:Implications for Subduction of Paleo-Pacific Plate

Magma mingling has been identified within the continental margin of southeastern China.This study focuses on the relationship between mafic and felsic igneous rocks in composite dikes and plutons in this area,and uses this relationship to examine the tectonic and geodynamic implications of the mingling of mafic and felsic magmas.Mafic magmatic enclaves（MMEs） show complex relationships with the hosting Xiaocuo granite in Fujian area,including lenticular to rounded porphyritic microgranular enclaves containing abundant felsic/mafic phenocrysts,elongate mafic enclaves,and back-veining of the felsic host granite into mafic enclaves.LA-ICP-MS zircon U-Pb analyses show crystallization of the granite and dioritic mafic magmatic enclave during ca.132 and 116 Ma.The host granite and MMEs both show zircon growth during repeated thermal events at-210 Ma and 160-180 Ma.Samples from the magma mingling zone generally contain felsic-derived zircons with well-developed growth zoning and aspect ratios of 2-3,and maficderived zircons with no obvious oscillatory zoning and with higher aspect ratios of 5-10.However,these two groups of zircons show no obvious trace element or age differences.The Hf-isotope compositions show that the host granite and MMEs have similar ε（Hf）（t） values from negative to positive which suggest a mixed source from partial melting of the Meso-Neoproterozoic with involvement of enriched mantlederived magmas or juvenile components.The lithologies,mineral associations,and geochemical characteristics of the mafic and felsic rocks in this study area indicate that both were intruded together,suggesting Early Cretaceous mantle—crustal interactions along the southeastern China continental margin.The Early Cretaceous magma mingling is correlated to subduction of Paleo-Pacific plate.

MAGMA软件辅助分析解决金属型薄壁铝合金壳体厚大部位的缩松缺陷

使用MAGMA软件对薄壁铝合金壳体低压砂芯金属型铸造的凝固过程进行模拟分析,发现通过在铸件局部厚大部位对应的金属型位置上设置紫铜镶块,同时在紫铜镶块与金属型间设置排气通道,可有效加强厚大部位的冷却速度和排气效果,减少薄壁铸件局部厚大部位产生缩松缺陷的可能性。

Origin and evolution of alkali basaltic magma in the Okinawa Trough

The contents of major element composition of the phenocrysts and the matrix glass as well as the spinel inclusions and the melt inclusion in the phenocrysts of the basalt dredged from Station 133 of the Okinawa Trough are determined by electron microprobe. The results show that the basalt is a dor- galite consisting of phenocrysts of bytownite, chrysolite, clinopyroxene and magnetite as well as labradorite microcrystal, matrix glass and a few bits of broken vein quartz. Glassy melt inclusion and chromohercynite or chrompleonaste exist in bytownite and chrysolite. The formation of the spinels is re- lated to partial melting of mantle. The melt inclusions stand for a primary alkali dorgalitic magma, whose composition corresponds to olivine gabbro. The basaltic magma was generated from partial melting of spinel-lherzolite of the upper mantle and evolved in a process of 'alkali dorgalitic magma-trachy- basaltic magma-basdaltic trachytic magma-trachytic magma'. Assimilation and hybridization of crustal material may exist during magma upwelling in every evolutionary stage.

Crystallization Conditions and Mineral Chemistry in the East of Tafresh, Central Iran, with Insights into Magmatic Processes

The Tafresh granitoids are located at the central part of the Urumieh-Dokhtar Magmatic Arc(UDMA)in Iran.These rocks,mainly consisting of diorite and granodiorite,were emplaced during the Early Miocene.They are composed of varying proportions of plagioclase+K-feldspar+hornblende±quartz±biotite.Discrimination diagrams and chemical indices of amphibole phases reveal a calc-alkaline affinity and fall clearly in the crust-mantle mixed source field.The estimated pressure,derived from Al in amphibole barometry,is approximately 3 Kb.The granitoids are I-type,metaluminous and belong to the calc-alkaline series.They are all enriched in light rare earth elements and large ion lithophile elements,depleted in high field strength elements and display geochemical features typical of subduction-related calc-alkaline arc magmas.Most crystal size distribution(CSD)line patterns from the granitoids show a non-straight trend which points to the effect of physical processes during petrogenesis.The presence of numerous mafic enclaves,sieve texture and oscillatory zoning along with the CSD results show that magma mixing in the magma chamber had an important role in the petrogenesis of Tafresh granitoids.Moreover,the CSD analysis suggests that the plagioclase crystals were crystallized in a time span of less than 1000 years,which is indicative of shallow depth magma crystallization.

Petro Gram: An excel-based petrology program for modeling of magmatic processes

Petro Gram is an Excel?based magmatic petrology program that generates numerical and graphical models.Petro Gram can model the magmatic processes such as melting,crystallization,assimilation and magma mixing based on the trace element and isotopic data.The program can produce both inverse and forward geochemical models for melting processes(e.g.forward model for batch,fractional and dynamic melting,and inverse model for batch and dynamic melting).However,the program uses a forward modeling approach for magma differentiation processes such as crystallization(EC:Equilibruim Crystallization,FC:Fractional Crystallization,IFC:Imperfect Fractional Crystallization and In-situ Crystallization),assimilation(AFC:Assimilation Fractional Crystallization,Decoupled FC-A:Decoupled Fractional Crystallization and Assimillation,A-IFC:Assimilation and Imperfect Fractional Crystallization)and magma mixing.One of the most important advantages of the program is that the melt composition obtained from any partial melting model can be used as a starting composition of the crystallization,assimilation and magma mixing.In addition,Petro Gram is able to carry out the classification,tectonic setting,multi-element(spider)and isotope correlation diagrams,and basic calculations including Mg^#,Eu/Eu^*,εSrandεNdwidely used in magmatic petrology.