Pseudosection modeling for the garnet amphibolite samples from the Western Dabie Mountains show they have experienced similar HP metamorphic evolution with that of the adjected eclogites.The common assemblage of
The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Z...The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should展开更多
Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic ma...Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.展开更多
The giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pi...The giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pit deposit according to exploration and research.The South Pit deposit is a high-grade Cu-Pb-Zn deposit,but its genesis is unclear.To investigate its genesis,a detailed study was conducted on the deposit geology,geochronology and amphibole geochemistry.The results indicate that the weighted average 206Pb/238U age of the zircons from the granite porphyry in the South Pit is 15.38±0.45 Ma,and the molybdenite from the mineralized skarn yield a ReOs isochron age of 15.23±0.22 Ma,in line with the age of the Main deposit(15.7-14.3 Ma).The amphiboles in the granite porphyry of the South Pit,magnesiohornblende and actinolite,are high in Mg and Ca and low in K.They crystallized at temperatures of 705-7490C,pressures of 0.44-0.67 kbar,oxygen fugacity of-14.31--13.69(NNO),and depths of 1.7-2.5 km.Mapping of structure and alteration indicates that the South Pit skarn developed due to the metasomatism of marble of hornfels or carbonate in fold hinge dilation and an interlayer detachment zone by magmatic hydrothermal fluids.According to the age of magmatism and geological features,the South Pit deposit and the Main deposit have originated from the same Miocene magmatism,but the South Pit deposit was affected by the gliding nappe tectonic system.The amphibole geochemistry indicates that the ore-related magma of the South Pit has a high oxygen fugacity and is rich in water.展开更多
Precambrian tectonic history of Zhejiaug,Fujian,and Jiangxi provinces of south China is important for understanding the tectonic evolution of South China but its magmatic activity,petrogenesis,stratigraphic sequence o...Precambrian tectonic history of Zhejiaug,Fujian,and Jiangxi provinces of south China is important for understanding the tectonic evolution of South China but its magmatic activity,petrogenesis,stratigraphic sequence of the Mamianshan Group is still strongly controversial.Here we present new sensitive high resolution ion micro-probe(SHRIMP)U-Pb zircon geochronological data for the Mamianshan Group and petrographical data to constrain the tectonic framework of the regions.Our results showed that the SHRIMP U-Pb zircon age of green schists of the Dongyan Formation is 796.5±9.3 Ma,the Daling Formation is 756.2±7.2 Ma,and mica-quartz schist of the Longbeixi Formation is 825.5±9.8 Ma.These data indicate that the Mamianshan Group was formed not in the Mesoproterozoic,but in the Neoproterozoic and its stratigraphic sequences should be composed of Longbeixi,Dongyan,and Daling Formations from the bottom to the top.Rocks from this Group,from Zhejiang,Fujian and Jiangxi provinces,constituted the upper basement of the Cathaysia Block that overlay the lower basement of the Mayuan Group.Detailed petrographic studies demonstrate that the amphibole schists of the Dongyan Formation in the Mamianshan Group were formed within an intra-arc rift setting rather than a continental rift as previously suggested.Rather,this island-arc type formation was developed by collision and/or subduction between various blocks resulting from the breakup of the supercontinent Rodinia at c.850-750 Ma.The Zhuzhou conglomerate,distributed near Dikou Town,Jian'ou City,Fujian Province and previously considered as evidence of the Mesoproterozoic Dikou movement,is shown here not to be the basal conglomerate above the angular unconformity between the upper and lower basements.Our conclusions have important implications for understanding the Precambrian tectonics of South China.展开更多
A reagent combination of sodium oleate(NaOl)and salicyl hydroximic acid was employed as the roughing and scavenging collectors,whereas styryl phosphoric acid(SPA)and octanol were employed as the cleaning collectors.Re...A reagent combination of sodium oleate(NaOl)and salicyl hydroximic acid was employed as the roughing and scavenging collectors,whereas styryl phosphoric acid(SPA)and octanol were employed as the cleaning collectors.Results of bench-scale flotation demonstrate that the dosage of SPA can be reduced by about 80%,and that a better flotation index can be obtained using the proposed reagent system.The results of adsorption amount and contact angle measurements indicate that the rutile surface adsorbed not only a large amount of residual NaOl but also SPA and a small amount of NaOl remained on the amphibole surface in strong acidic solution.The hydrophobic difference between rutile and amphibole surfaces was therefore amplified in cleaning,and their further separation became much easier consequently.展开更多
ABSTRACT： The joint methods of ^40Ar/^39Ar laser stepwise heating and in vacuo crushing have been applied to date amphiboles from the North Qaidam ultra-high pressure metamorphic amphibolites. Two amphibole samples a...ABSTRACT： The joint methods of ^40Ar/^39Ar laser stepwise heating and in vacuo crushing have been applied to date amphiboles from the North Qaidam ultra-high pressure metamorphic amphibolites. Two amphibole samples analyzed by laser heating yielded saddle-shaped age spectra with total gas ages of 574.5±2.5 and 562.5=±2.5 Ma. These ages are much older than the reported zircon U-Pb ages （-495 Ma） from Yuka eclogite, indicating the presence of excess ^40Ar. In order to decipher the occur- rence of excess ^40Ar and constrain the age of amphibolite-facies retrogression, two duplicate amphibole samples were further employed for ^40Ar/^39Ar in vacuo crushing analyses. Both samples exhibit similar monotonically declining release spectra, which are characterized by rapid decline of anomalously old apparent ages in the early steps. The data of the late steps yielded concordant apparent ages with pla- teau ages of 460.9±1.2 and 459.6±1.8 Ma. We interpret that gases released in the early steps derive from the significant excess ^40Ar containing secondary fluid inclusions （SFIs） due to their distribution characteristics along cracks leading to be easily extracted, whereas those released in the later steps rep- resent the contribution of the small primary fluid inclusions （PFIs）.展开更多
We present here for the first time,the Raman and infrared spectroscopic investigation of amphiboles from the World's deepest borehole,the Kola super-deep borehole,at the depth of 11.66 km.The Kola Super-deep boreh...We present here for the first time,the Raman and infrared spectroscopic investigation of amphiboles from the World's deepest borehole,the Kola super-deep borehole,at the depth of 11.66 km.The Kola Super-deep borehole(SG-3)(henceforth referred as KSDB)is located in the northwest of the Kola Peninsula in the northern frame of the Pechenga structure,Russia.It was drilled in the north-eastern part of the Baltic Shield(69о5’N,30о44’E)and reached a depth of 12.262 km.It has been drilled in the northern limb of the Pechenga geosyncline composed of rhythmically inter-bedded volcanogenic and tuffaceous-sedimentary strata extending to the NW at 300°–310°and dipping to SW at angles of 30°–50°.The SG-3 geological section is represented by two complexes–Proterozoic and Archaean.Amphibolite facies is dominant in the depth region from 6000 m to 12,000m to the deepest.The Raman spectra of the sample reveal abundant presence of plagioclase and amphiboles.The most distinct Raman peak in this study indicates the tremolite-ferro-actinolite rich enrichment of the borehole samples at this depth corroborating earlier conventional petrographic studies.展开更多
Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is c...Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is classified as a transitional LIP. In this study, we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA, LA-ICPMS, CCD single crystal diffraction, and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase, amphibole, apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements(HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams, they show pronounced Th and U spikes and Nb, Zr, Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole, indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts, suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock, and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.展开更多
Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts,bel...Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts,belonging mainly to pargasite and magnesiohastingsite, are characteristic of the amphibole composition derived from mantle and crystallized in lower crust. In general, the aggregates of pyrrhotite-chalcopyrite take the shapes of cylinder and sphere. Three occurrences have been recognized in the amphibole megacrysts: parallel linear, bunchy and scattered. The unique cylinder-like shape of the aggregates and remarkable Ni-poor sulfides in Caoshan are distinctively different from the spherical Ni-rich sulfides in pyroxene megacrysts and any other kinds of megacrysts. In terms of composition, the amphibole megacrysts and their sulfides in Caoshan are similar to those in the pyroxenite xenoliths in Qilin, Guangdong Province. In terms of origin, the pyrrhotite-chalcopyrites as exsolution products resulted from the subsolidus re-equilibration of sulfide solid solution within amphibole megacrysts. Such pyrrhotite-chalcopyrite-bearing amphibole megacrysts were first discovered inside and outside China. This discovery is important for the study of regional magma evolution and its associated mineralizations and ore sources as well.展开更多
Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemist...Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite（Si〈7.1）, chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P-T conditions are estimated as T=350–400 ℃ and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing＇an blocks situated in the eastern portions of the Central Asia Orogenic Belt（CAOB）.展开更多
To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed....To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed. The trace element compositions in clinopyroxenes indicate the existence of the mantle protolith of two types. The first protolith type, represented by lherzolites and diopside harzburgites,was originated from the partial melting(5%–10%) under the spinel facies conditions, while the second one,represented by diopside harzburgites, was formed under the polybaric partial melting(17%–19%) under garnet and spinel facies conditions. Subsequently, the mantle peridotite protolith was subject to fluidinduced partial melting in the suprasubduction setting that was resulted in the formation of harzburgites.Being affected by penetrating melts and fluids peridotites experienced the refertilization(LREE enrichment of clinopyroxenes) and high-temperature hydratation with subsequent development of pargasite and Mg amphibole. The high-T fluid-induced metamorphism at the subduction zone was accompanied by the formation of metaperidotites with clinochlore and REE-depleted tremolite.展开更多
Amphibole is a rock-forming mineral widely existing on the earth.It is easily dissolved and altered during the later stage of diagenesis and mineralization,and often forms chloritization,which is an important indicato...Amphibole is a rock-forming mineral widely existing on the earth.It is easily dissolved and altered during the later stage of diagenesis and mineralization,and often forms chloritization,which is an important indicator for prospecting.To explore amphibole's dissolution process and alteration mechanism,dissolution experiments were carried out under acidic conditions using pargasite-rich amphibole as raw material,and the effects of temperature,p H,and experiment duration on amphibole alteration were investigated.Experimental samples and products were analyzed using X-ray diffractometer,field emission scanning electron microscope,electron probe micro analyzer,and transmission electron microscopy.It was found that many pores and erosion edges are produced after amphibole dissolution,and there is a clear interface between the dissolved residual portion and the parent.The dissolved residual portion remains in the amphibole phase,but as the temperature and time increase,the intensity of the diffraction peak of the phase in the product decreases,and the peak position shifts to a small angle.Many clay minerals such as chlorite and griffithite formed on the amphibole surface.In an environment with strong acidity(p H=3),the amount of chamosite increases with temperature(180℃→210℃→240℃),whereas clinochlore is only increased in a 150–210℃environment.Griffithite growth was observed in the acidic(p H=6)and low temperature(<180℃)environments.Based on this analysis,large radius Cl–enters the amphibole lattice or cracks to promote dissolution.The Al-poor and Ca-and Fe-rich regions between the edge and core of the amphibole are caused by dynamic equilibrium in amphibole dissolution and alteration process,which is an essential indicator for the beginning of amphibole dissolution-alteration.Diffusion and the coupled dissolution-reprecipitation mechanism accomplishes the process of dissolution and alteration to form clay minerals.The energy of the system determined by temperature and p H is the key to controlling the rate of growth and nucleation of clay minerals.High temperature and strong acidity will dissolve more iron from amphibole,which is conducive to chlorite growth.Compared to chlorite,griffithite is more sensitive to temperature.Griffithite attaches on the amphibole surface with a star-like in a weak acid and low-temperature environment.The results of this study can provide a mineralogical basis for the analysis of hydrothermal alteration processes and the division of alteration zones.展开更多
New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This comp...New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This complex is characterized by discontinuous ring-shaped outcrops cut by later faulting. The A-type rocks of the AIC are late Neoproterozoic post-collisional granites, including alkali feldspar granite, alkaline granite and peralkaline granite. They represent the outer zones of the AIC, surrounding a core of older rocks including monzogranite, syenogranite and granophyre granite. The sharp contacts between A-type granites of the outer zone and the different granitic rocks of the inner zone suggest that the AIC was emplaced as different phases over a time interval, following complete crystallization of earlier batches. The A-type granites represent the late intrusive phases of the AIC, which were emplaced during tectonic extension, as shown by the emplacement of dykes synchronous with the granite emplacement and the presence of cataclastic features. The A-type granites consist of K-feldspars, quartz, albite, amphiboles and sodic pyroxene with a wide variety of accessory minerals, including Fe-Ti oxides, zircon, allanite, fluorite, monazite, titanite, apatite, columbite, xenotime and epidote. They are highly evolved(71.3–75.8 wt% SiO2) and display the typical geochemical characteristics of post-collisional, within-plate granites. They are rare-metal granites enriched in total alkalis, Nb, Zr, Y, Ga, Ta, REE with low CaO, MgO, Ba, and Sr. Eu-negative anomalies(Eu/Eu* = 0.17–0.37) of the A-type granites reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interactions. The chemical characteristics indicate that the A-type granites of the AIC represent products of extreme fractional crystallization involving alkali feldspar, quartz and, to a lesser extent, ferromagnesian minerals. The parent magma was derived from the partial melting of a juvenile crustal protolith with a mantle contribution. Accumulation of residual volatile-rich melt and exsolved fluids in the late stage of the magma evolution produced pegmatite and quartz veins that cut the peripheries of the AIC. Post-magmatic alteration related to the final stages of the evolution of the A-type granitic magma, indicated by alterations of sodic amphibole and sodic pyroxene, hematitization and partial albitization.展开更多
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 assortme...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.展开更多
Metabasite refers to metamorphosed basalts and other mafic igneous rocks (rich in iron and magnesium). When a mafic igneous rock is subjected to new pressure and temperature conditions during metamorphism, these chemi...Metabasite refers to metamorphosed basalts and other mafic igneous rocks (rich in iron and magnesium). When a mafic igneous rock is subjected to new pressure and temperature conditions during metamorphism, these chemical components will rearrange themselves to form new minerals. Metabasites can be found in many metamorphic belts including Sanandaj-Sirjan metamorphic belt of Iran. The study area is a Tanbour metamorphic complex in Eastern of Sirjan city, which is geologically located at the Sanandaj-Sirjan metamorphic belt in Southern Iran. Metabasite in this complex consists of greenschist, epidote amphibolite and amphibolite. Amphibole and plagioclase are the main minerals in the greenschist and amphibolite, and the a secondary mineral in some micaschist seen in the study area. The electron microprobe analysis was done on this mineralization in greenschist, epidote amphibolite and amphibolite, which showed that the amphiboles in greenschist was a member of the calcic group and Actinolite type, and the amphiboles in epidote amphibolite was a member of the calcic group and these amphiboles were tschermakite up to Ferro-Tschermakite + Ferro-Hornblende type. The amphibole in amphibolite is a member of the calcic group and this amphibole is Magnesio-Hornblende type. The plagioclases in the greenschist is pure albite (An 3.29 - 3.6), and in the epidote amphibolite is oligoclase (An 19.5 - 24.2), while in the amphibolites is oligoclase (An 16.9 - 26.6). The estimated P–T conditions are in favor of their metamorphism under epidote amphibolite (550°C and 8 kbar) and amphibolite (611°C - 652° Cand 10.5 kbar) facies.展开更多
Partitioning behavior between amphibole and silicate glass of thirty-three minor and trace elements(Sc,Ti, V, Cr, Co, Rb, Sr, P, Y, Zr, Nb, Cs, Ba, K, La, Ce, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb,...Partitioning behavior between amphibole and silicate glass of thirty-three minor and trace elements(Sc,Ti, V, Cr, Co, Rb, Sr, P, Y, Zr, Nb, Cs, Ba, K, La, Ce, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb,Th, and U) have been determined experimentally. Products of crystallization of hydrous basalt melts from 0.6 GPa/860 °C up to 2.6 GPa/970 °C were obtained in a multianvil apparatus. Major and trace element compositions of amphibole and glass were determined with a combination of electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The main mineral phase is calcic amphibole, and the coexisting glass compositions are tonalite, granodiorite, and granite. The compatibility of rare earth elements increase at 915 °C and then decrease at 970 °C, but the compatibility of most of these elements shows a continued, significant increase with increasing pressure. For high-field strength elements, large ion lithophile elements, actinide compatibility decrease with increasing temperature or pressure, but transition metals show a continued increase in compatibility within the temperature–pressure conditions. From mathematical and graphical fitting, we determined best-fit values for the ideal ionic radius(r_0, 1.01–1.04 ?), the strain-free partitioncoefficient(D_0, 1.18–1.58), and apparent Young's modulus(E, 142–370 GPa) for the M4 site in amphibole according to the lattice strain model. The D_0^(M4) for rare earth elements rises at 915 °C and then drops at 970 °C at 0.6 GPa.However, the D_0^(M4) values are positively proportional to the pressure for rare earth elements in the amphibole-glass pairs at 0.6–2.6 GPa and 970 °C. Furthermore, the derived best-fit values for r_0^(M4) and E^(M4) are almost constant and trend to increase with rising temperature and pressure,respectively. The partition coefficient is distinctly different for different melt compositions. The rare earth elements become more enriched in amphibole if the quenched glass is granodiorite or granite compared to the tonalitic glasses.展开更多
Pasveh gabbros are mafic component of a plutonic complex in the northwest Sanandaj- Sirjan Zone. These cumulative rocks are composed of plagioclase and calcic clinopyroxene （Cpx）, which yield unusually high CaO （〉...Pasveh gabbros are mafic component of a plutonic complex in the northwest Sanandaj- Sirjan Zone. These cumulative rocks are composed of plagioclase and calcic clinopyroxene （Cpx）, which yield unusually high CaO （〉19 wt.%） in whole-rock chemistry. Petrographical and geochemical data suggest that Pasveh gabbros can be divided into two groups： free scapolite and scapolite-bearing gabbros. The second group has higher Na20, K20, and P205 relative to free scapolite ones and is enriched in LIL （large ion lithophile） and HFS （high field strength） elements. Two stages of metasomatism affected the primary composition of mafic rocks. Firstly, high temperature reaction caused to invert primary high Ti clinopyroxene to low Ti cUnopyroxene＋high Ti amphibole. This reaction was extensive and included all gabbroic samples. Hydrothermal fluids involved in this process can be derived from dehydration reactions of country rocks or from other magmas incorporated in the formation of Pasveh complex pluton. The second metasomatic stage relates to scapolitization of limited parts of gabbroic rocks. An external saline fluid, which is composed of major NaCI and minor KCI and P205 components, impacted locally on Pasveh gabbros and formed the second metasomatic stage. Possible sources of Na and Cl are primary evaporites or brines, which were present in the host sediments of the gabbros. The carbonate-free nature of these hydrothermal fluids suggests that hydrothermal fluids responsible for the formation of scapolite in Pasveh gabbros are derived from marine evaporitic parentage.展开更多
Over a 70-year period, a mine near Libby, MT supplied nearly 80% of the world’s vermiculite. Raw vermiculite, which was contaminated with naturally occurring amphibole in veins throughout the deposit, was shipped to ...Over a 70-year period, a mine near Libby, MT supplied nearly 80% of the world’s vermiculite. Raw vermiculite, which was contaminated with naturally occurring amphibole in veins throughout the deposit, was shipped to processing sites throughout the United States for exfoliation. In this pilot study, tree bark samples were collected near processing facilities in Spokane, WA, Santa Ana, CA, Newark, CA, and Phoenix, AZ in an effort to determine if areas surrounding these facilities are today contaminated with Libby amphibole asbestos (AA). From areas surrounding each of the four historical processing sites, Libby AA was detected in a subset of the bark samples. At the Santa Ana, Newark and Phoenix facilities, actinolite-tremolite and other high Fe Ca-bearing amphibole were also measured from the bark samples. In addition, chrysotile was frequently measured in samples collected from each of the sites. From the results of this pilot study, it is evident that tree bark can serve as reservoirs of asbestos, and indicators of past and current contamination. These data also suggest that areas outside of these historical processing facilities may today have some level of existing contamination resulting from the operation of these facilities.展开更多
Crocidolite,amosite,anthophyllite,tremolite,actinolite besides the chrysotile serpentine polymorph fall within the classification of asbestos,whose commercial use is banned,and environmental and human exposure levels ...Crocidolite,amosite,anthophyllite,tremolite,actinolite besides the chrysotile serpentine polymorph fall within the classification of asbestos,whose commercial use is banned,and environmental and human exposure levels regulated.However,the cited amphibole species can crystallise in asbestiform or non-asbestiform habit and therefore their morphological characterization has a key role in assessing a reliable asbestos hazard scenario.Furthermore,when a mechanical stress is applied to rocks containing pristine prismatic or acicular amphiboles,these phases can break,originating particles with dimensions and geometrical ratios that would label them as asbestos.Therefore,a normative and scientific crucial gap arise in the classification criteria of a particle as a real asbestiform mineral or as a cleavage fragment(i.e.non-asbestos).The mode of comminution is fundamental for the following quantitative determination of fibres.It is critical because it can affect the morphology and geometric ratios of fibres,inducing positive or negative falses.In this framework,our work was focused on the Scanning Electron Microscopy coupled with Energy Dispersive Spettroscopy(SEM-EDS)analysis of amphiboles with asbestiform and non-asbestiform habit,subject to mechanical stress for three different time intervals,in order to assess how different time lengths of comminution control geometry and morphology of the particles.展开更多
文摘Pseudosection modeling for the garnet amphibolite samples from the Western Dabie Mountains show they have experienced similar HP metamorphic evolution with that of the adjected eclogites.The common assemblage of
文摘The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should
文摘Field-and petrographic investigations,together with microanalytical major-and traceelement studies,were carried out on clinopyroxene and amphibole from high-Mg diorite in the subduction-related Chelyabinsk granitic massif to understand its petrogenesis and source.The clinopyroxene composition(high Mg#,Cr-content,sum of REE and Ti/Eu ratio;depletion in HREE;negative Eu-anomaly)indicates that it formed from a reduced melt derived from a mantle source metasomatized by fluids/melts having crustal affinity.Melt compositions in equilibrium with clinopyroxene and amphibole were calculated using solid/liquid partition coefficients.The high Nb/Y and Zr/Y ratio values of a liquid simulated from clinopyroxene,which appears to have very similar characteristics to sanukitoid melts,indicate a low degree of melting of the mantle source.Melt simulated from amphibole is more evolved and more felsic(dacitic).It displays a geochemical“amphibole fractionation”signature,indicating the peritectic transformation of clinopyroxene to amphibole in the lower crust.Rock textures and major element mineral compositions suggest that further amphibole was precipitated directly from the melt in the middle crust.The results show that the Chelyabinsk highMg diorite was probably formed as a cumulate from sanukitoid-like melt during its ascent and cooling below dacitic liquidus inside the amphibole stability field.
基金supported by the National Key Research and Development Program of China(No.2022YFC2905004)Open Fund from Sino Probe Laboratory(No.SL202405)+4 种基金the Basic Research Fund of Institute of mineral Resource,Chinese Academy of Geological Sciences(No.JKYZD202316)the National Natural Science Foundation of China(Nos.42272093,42230813)China Scholarship Council Project,and the Geological Survey Project(No.DD20230054)Science and Technology Support Project in a new round of prospecting breakthrough strategic action(No.ZKKJ202429)the Central Government Guided Local Scientific and Technological Development Funding Project(No.XZ202401YD0006)。
文摘The giant Jiama deposit is a post-collisional porphyry Cu-polymetallic system located in the Gangdese metallogenic belt of Xizang.It consists of three deposits:The Main deposit,the Zegulangbei deposit,and the South Pit deposit according to exploration and research.The South Pit deposit is a high-grade Cu-Pb-Zn deposit,but its genesis is unclear.To investigate its genesis,a detailed study was conducted on the deposit geology,geochronology and amphibole geochemistry.The results indicate that the weighted average 206Pb/238U age of the zircons from the granite porphyry in the South Pit is 15.38±0.45 Ma,and the molybdenite from the mineralized skarn yield a ReOs isochron age of 15.23±0.22 Ma,in line with the age of the Main deposit(15.7-14.3 Ma).The amphiboles in the granite porphyry of the South Pit,magnesiohornblende and actinolite,are high in Mg and Ca and low in K.They crystallized at temperatures of 705-7490C,pressures of 0.44-0.67 kbar,oxygen fugacity of-14.31--13.69(NNO),and depths of 1.7-2.5 km.Mapping of structure and alteration indicates that the South Pit skarn developed due to the metasomatism of marble of hornfels or carbonate in fold hinge dilation and an interlayer detachment zone by magmatic hydrothermal fluids.According to the age of magmatism and geological features,the South Pit deposit and the Main deposit have originated from the same Miocene magmatism,but the South Pit deposit was affected by the gliding nappe tectonic system.The amphibole geochemistry indicates that the ore-related magma of the South Pit has a high oxygen fugacity and is rich in water.
基金National Natural Science Foundation of China(Grant No.40772134)for financial support
文摘Precambrian tectonic history of Zhejiaug,Fujian,and Jiangxi provinces of south China is important for understanding the tectonic evolution of South China but its magmatic activity,petrogenesis,stratigraphic sequence of the Mamianshan Group is still strongly controversial.Here we present new sensitive high resolution ion micro-probe(SHRIMP)U-Pb zircon geochronological data for the Mamianshan Group and petrographical data to constrain the tectonic framework of the regions.Our results showed that the SHRIMP U-Pb zircon age of green schists of the Dongyan Formation is 796.5±9.3 Ma,the Daling Formation is 756.2±7.2 Ma,and mica-quartz schist of the Longbeixi Formation is 825.5±9.8 Ma.These data indicate that the Mamianshan Group was formed not in the Mesoproterozoic,but in the Neoproterozoic and its stratigraphic sequences should be composed of Longbeixi,Dongyan,and Daling Formations from the bottom to the top.Rocks from this Group,from Zhejiang,Fujian and Jiangxi provinces,constituted the upper basement of the Cathaysia Block that overlay the lower basement of the Mayuan Group.Detailed petrographic studies demonstrate that the amphibole schists of the Dongyan Formation in the Mamianshan Group were formed within an intra-arc rift setting rather than a continental rift as previously suggested.Rather,this island-arc type formation was developed by collision and/or subduction between various blocks resulting from the breakup of the supercontinent Rodinia at c.850-750 Ma.The Zhuzhou conglomerate,distributed near Dikou Town,Jian'ou City,Fujian Province and previously considered as evidence of the Mesoproterozoic Dikou movement,is shown here not to be the basal conglomerate above the angular unconformity between the upper and lower basements.Our conclusions have important implications for understanding the Precambrian tectonics of South China.
基金Projects(11575281,11290165,11305252,U1532260,51474254)supported by the National Natural Science Foundation of China
文摘A reagent combination of sodium oleate(NaOl)and salicyl hydroximic acid was employed as the roughing and scavenging collectors,whereas styryl phosphoric acid(SPA)and octanol were employed as the cleaning collectors.Results of bench-scale flotation demonstrate that the dosage of SPA can be reduced by about 80%,and that a better flotation index can be obtained using the proposed reagent system.The results of adsorption amount and contact angle measurements indicate that the rutile surface adsorbed not only a large amount of residual NaOl but also SPA and a small amount of NaOl remained on the amphibole surface in strong acidic solution.The hydrophobic difference between rutile and amphibole surfaces was therefore amplified in cleaning,and their further separation became much easier consequently.
基金funded by the National Natural Science Foundation of China (Nos. 41703054, 41503053)the Guangxi Natural Science Foundation Program (Nos. 2016GXNSFCA380022, 2014GXNSFBA118231)the Chinese Academy of Sciences-Royal Netherlands Academy of Arts and Sciences Joint PhD Training Programme (No. O8PhD-08)
文摘ABSTRACT： The joint methods of ^40Ar/^39Ar laser stepwise heating and in vacuo crushing have been applied to date amphiboles from the North Qaidam ultra-high pressure metamorphic amphibolites. Two amphibole samples analyzed by laser heating yielded saddle-shaped age spectra with total gas ages of 574.5±2.5 and 562.5=±2.5 Ma. These ages are much older than the reported zircon U-Pb ages （-495 Ma） from Yuka eclogite, indicating the presence of excess ^40Ar. In order to decipher the occur- rence of excess ^40Ar and constrain the age of amphibolite-facies retrogression, two duplicate amphibole samples were further employed for ^40Ar/^39Ar in vacuo crushing analyses. Both samples exhibit similar monotonically declining release spectra, which are characterized by rapid decline of anomalously old apparent ages in the early steps. The data of the late steps yielded concordant apparent ages with pla- teau ages of 460.9±1.2 and 459.6±1.8 Ma. We interpret that gases released in the early steps derive from the significant excess ^40Ar containing secondary fluid inclusions （SFIs） due to their distribution characteristics along cracks leading to be easily extracted, whereas those released in the later steps rep- resent the contribution of the small primary fluid inclusions （PFIs）.
基金National Institute of advanced Studies (NIAS)Indian National Science Academy (INSA) for the support in under the INSA senior Scientist scheme.
文摘We present here for the first time,the Raman and infrared spectroscopic investigation of amphiboles from the World's deepest borehole,the Kola super-deep borehole,at the depth of 11.66 km.The Kola Super-deep borehole(SG-3)(henceforth referred as KSDB)is located in the northwest of the Kola Peninsula in the northern frame of the Pechenga structure,Russia.It was drilled in the north-eastern part of the Baltic Shield(69о5’N,30о44’E)and reached a depth of 12.262 km.It has been drilled in the northern limb of the Pechenga geosyncline composed of rhythmically inter-bedded volcanogenic and tuffaceous-sedimentary strata extending to the NW at 300°–310°and dipping to SW at angles of 30°–50°.The SG-3 geological section is represented by two complexes–Proterozoic and Archaean.Amphibolite facies is dominant in the depth region from 6000 m to 12,000m to the deepest.The Raman spectra of the sample reveal abundant presence of plagioclase and amphiboles.The most distinct Raman peak in this study indicates the tremolite-ferro-actinolite rich enrichment of the borehole samples at this depth corroborating earlier conventional petrographic studies.
基金the National Natural Science Foundation of China (Nos. 41772057, 41702064)the Fundamental Research Funds for the Central Universities (Nos. 2652018118, PA2018GDQT0020)。
文摘Unlike the typical large igneous provinces(LIPs) that are dominated by mafic-ultramafic rocks, the Tarim large igneous province(TLIP) is characterized by a high proportion of felsic rocks, based on which the TLIP is classified as a transitional LIP. In this study, we focus on the trachydacite from the TLIP in which we report the characteristics of hisingerite employing a variety of techniques such as EMPA, LA-ICPMS, CCD single crystal diffraction, and bulk-rock oxygen isotopes. The hisingerite in this rock is associated with plagioclase, amphibole, apatite and ilmenite. These minerals occur as aggregates of fine curled fibers in micron-scale and display heavy rare earth elements(HREE) enriched signature with significant negative Eu anomalies. In the primitive mantle-normalized trace element spider diagrams, they show pronounced Th and U spikes and Nb, Zr, Hf troughs. Petrological observation and mineralogical study reveal a closely genetic relationship between hisingerite and amphibole, indicating that the hisingerite might have been derived from the breakdown of amphibole during the magma ascent. The formation of hisingerite requires excess water from the surrounding melts, suggesting a hydrous parental magma. The hisingerite and amphibole assign a hydrous crustal source for the rock, and extensive crustal melting accounts for the voluminous felsic rocks in the TLIP.
文摘Some pyrrhotite-chalcopyrite-bearing amphibole megacrysts (including pyroxene megacrysts) were discovered in Mesozoic augite diorite-porphyrite at Caoshan in Tongling area, Anhui Province. The amphibole megacrysts,belonging mainly to pargasite and magnesiohastingsite, are characteristic of the amphibole composition derived from mantle and crystallized in lower crust. In general, the aggregates of pyrrhotite-chalcopyrite take the shapes of cylinder and sphere. Three occurrences have been recognized in the amphibole megacrysts: parallel linear, bunchy and scattered. The unique cylinder-like shape of the aggregates and remarkable Ni-poor sulfides in Caoshan are distinctively different from the spherical Ni-rich sulfides in pyroxene megacrysts and any other kinds of megacrysts. In terms of composition, the amphibole megacrysts and their sulfides in Caoshan are similar to those in the pyroxenite xenoliths in Qilin, Guangdong Province. In terms of origin, the pyrrhotite-chalcopyrites as exsolution products resulted from the subsolidus re-equilibration of sulfide solid solution within amphibole megacrysts. Such pyrrhotite-chalcopyrite-bearing amphibole megacrysts were first discovered inside and outside China. This discovery is important for the study of regional magma evolution and its associated mineralizations and ore sources as well.
基金supported by 973 program (No.2013CB429802) to Y.J.Liuthe National Natural Science Foundation of China (Grant 41302175) to W.M.LiJilin University and JSPS Grant-in-Aid for Scientific Research (Nos.17340149, 24340124) to A.Takasu, Shimane University, Japan
文摘Blueschist accompanied by pelitic schist expose along the Xinlin-Xiguitu fault in the Toudaoqiao area, northeastern China. In this paper, the blueschist is systematically studied on the petrography and mineral chemistry. The amphiboles in the blueschist are zoned from winchite core to magnesioriebeckite/glaucophane rim to winchite outermost rim. The peak metamorphic conditions are defined by the mineral assemblage of magnesioriebeckite/glaucophane, epidote, high-Si phengite（Si〈7.1）, chlorite, albite, hematite and quartz, indicating an epidote-blueschist facies metamorphism. The P-T conditions are estimated as T=350–400 ℃ and P=10-12 kbar. The occurrence of the blueschist along the Xinlin-Xiguitu fault strongly suggests the fault is the suture between the Ergun and the Xing＇an blocks situated in the eastern portions of the Central Asia Orogenic Belt（CAOB）.
基金the Project IGCP-649 and the IGG UB RAS (No. АААА-А18118052590029-6)
文摘To discuss the nature of the compositional heterogeneity of the peridotite massifs of the Polar Urals(Russia), the geochemical study by LA-ICP-MS of pyroxenes and amphiboles from these mantle formations was performed. The trace element compositions in clinopyroxenes indicate the existence of the mantle protolith of two types. The first protolith type, represented by lherzolites and diopside harzburgites,was originated from the partial melting(5%–10%) under the spinel facies conditions, while the second one,represented by diopside harzburgites, was formed under the polybaric partial melting(17%–19%) under garnet and spinel facies conditions. Subsequently, the mantle peridotite protolith was subject to fluidinduced partial melting in the suprasubduction setting that was resulted in the formation of harzburgites.Being affected by penetrating melts and fluids peridotites experienced the refertilization(LREE enrichment of clinopyroxenes) and high-temperature hydratation with subsequent development of pargasite and Mg amphibole. The high-T fluid-induced metamorphism at the subduction zone was accompanied by the formation of metaperidotites with clinochlore and REE-depleted tremolite.
基金funded by the National Natural Science Foundation of China (41272062)Key Laboratory of Earth and Planetary Physics (IGGCAS, DQXX201706)+2 种基金The Fundamental Research Funds for the Central Universities (N170106001)National Nonprofit Institute Research Grant (IGGE, AS2017J13)China Postdoctoral Science Foundation (2019M651136)
文摘Amphibole is a rock-forming mineral widely existing on the earth.It is easily dissolved and altered during the later stage of diagenesis and mineralization,and often forms chloritization,which is an important indicator for prospecting.To explore amphibole's dissolution process and alteration mechanism,dissolution experiments were carried out under acidic conditions using pargasite-rich amphibole as raw material,and the effects of temperature,p H,and experiment duration on amphibole alteration were investigated.Experimental samples and products were analyzed using X-ray diffractometer,field emission scanning electron microscope,electron probe micro analyzer,and transmission electron microscopy.It was found that many pores and erosion edges are produced after amphibole dissolution,and there is a clear interface between the dissolved residual portion and the parent.The dissolved residual portion remains in the amphibole phase,but as the temperature and time increase,the intensity of the diffraction peak of the phase in the product decreases,and the peak position shifts to a small angle.Many clay minerals such as chlorite and griffithite formed on the amphibole surface.In an environment with strong acidity(p H=3),the amount of chamosite increases with temperature(180℃→210℃→240℃),whereas clinochlore is only increased in a 150–210℃environment.Griffithite growth was observed in the acidic(p H=6)and low temperature(<180℃)environments.Based on this analysis,large radius Cl–enters the amphibole lattice or cracks to promote dissolution.The Al-poor and Ca-and Fe-rich regions between the edge and core of the amphibole are caused by dynamic equilibrium in amphibole dissolution and alteration process,which is an essential indicator for the beginning of amphibole dissolution-alteration.Diffusion and the coupled dissolution-reprecipitation mechanism accomplishes the process of dissolution and alteration to form clay minerals.The energy of the system determined by temperature and p H is the key to controlling the rate of growth and nucleation of clay minerals.High temperature and strong acidity will dissolve more iron from amphibole,which is conducive to chlorite growth.Compared to chlorite,griffithite is more sensitive to temperature.Griffithite attaches on the amphibole surface with a star-like in a weak acid and low-temperature environment.The results of this study can provide a mineralogical basis for the analysis of hydrothermal alteration processes and the division of alteration zones.
基金The authors extend their appreciation to the Deanship of Scientific ResearchHa’il Universityfor supporting this work through research project no.SCB-0150175
文摘New fieldwork, mineralogical and geochemical data and interpretations are presented for the rare-metal bearing A-type granites of the Aja intrusive complex(AIC) in the northern segment of the Arabian Shield. This complex is characterized by discontinuous ring-shaped outcrops cut by later faulting. The A-type rocks of the AIC are late Neoproterozoic post-collisional granites, including alkali feldspar granite, alkaline granite and peralkaline granite. They represent the outer zones of the AIC, surrounding a core of older rocks including monzogranite, syenogranite and granophyre granite. The sharp contacts between A-type granites of the outer zone and the different granitic rocks of the inner zone suggest that the AIC was emplaced as different phases over a time interval, following complete crystallization of earlier batches. The A-type granites represent the late intrusive phases of the AIC, which were emplaced during tectonic extension, as shown by the emplacement of dykes synchronous with the granite emplacement and the presence of cataclastic features. The A-type granites consist of K-feldspars, quartz, albite, amphiboles and sodic pyroxene with a wide variety of accessory minerals, including Fe-Ti oxides, zircon, allanite, fluorite, monazite, titanite, apatite, columbite, xenotime and epidote. They are highly evolved(71.3–75.8 wt% SiO2) and display the typical geochemical characteristics of post-collisional, within-plate granites. They are rare-metal granites enriched in total alkalis, Nb, Zr, Y, Ga, Ta, REE with low CaO, MgO, Ba, and Sr. Eu-negative anomalies(Eu/Eu* = 0.17–0.37) of the A-type granites reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interactions. The chemical characteristics indicate that the A-type granites of the AIC represent products of extreme fractional crystallization involving alkali feldspar, quartz and, to a lesser extent, ferromagnesian minerals. The parent magma was derived from the partial melting of a juvenile crustal protolith with a mantle contribution. Accumulation of residual volatile-rich melt and exsolved fluids in the late stage of the magma evolution produced pegmatite and quartz veins that cut the peripheries of the AIC. Post-magmatic alteration related to the final stages of the evolution of the A-type granitic magma, indicated by alterations of sodic amphibole and sodic pyroxene, hematitization and partial albitization.
基金acknowledge the DST-SERB grant Project No.CRG/2020/002635,DST-INSPIRE fellowship No.IF210186.
文摘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.
文摘Metabasite refers to metamorphosed basalts and other mafic igneous rocks (rich in iron and magnesium). When a mafic igneous rock is subjected to new pressure and temperature conditions during metamorphism, these chemical components will rearrange themselves to form new minerals. Metabasites can be found in many metamorphic belts including Sanandaj-Sirjan metamorphic belt of Iran. The study area is a Tanbour metamorphic complex in Eastern of Sirjan city, which is geologically located at the Sanandaj-Sirjan metamorphic belt in Southern Iran. Metabasite in this complex consists of greenschist, epidote amphibolite and amphibolite. Amphibole and plagioclase are the main minerals in the greenschist and amphibolite, and the a secondary mineral in some micaschist seen in the study area. The electron microprobe analysis was done on this mineralization in greenschist, epidote amphibolite and amphibolite, which showed that the amphiboles in greenschist was a member of the calcic group and Actinolite type, and the amphiboles in epidote amphibolite was a member of the calcic group and these amphiboles were tschermakite up to Ferro-Tschermakite + Ferro-Hornblende type. The amphibole in amphibolite is a member of the calcic group and this amphibole is Magnesio-Hornblende type. The plagioclases in the greenschist is pure albite (An 3.29 - 3.6), and in the epidote amphibolite is oligoclase (An 19.5 - 24.2), while in the amphibolites is oligoclase (An 16.9 - 26.6). The estimated P–T conditions are in favor of their metamorphism under epidote amphibolite (550°C and 8 kbar) and amphibolite (611°C - 652° Cand 10.5 kbar) facies.
基金financial support of the National Natural Science Foundation of China (Grant Nos. 41274105 and 41772043)the Joint Research Fund in Huge Scientific Equipment (U1632112) under cooperative agreement between NSFC and CAS+6 种基金the Chinese Academy of Sciences ‘‘Light of West China’’ Program (Dawei Fan, 2017)Youth Innovation Promotion Association CAS (Dawei Fan, 2018)the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB 18010401)the CPSF-CAS Joint Foundation for Excellent Postdoctoral Fellows (Grant No. 2017LH014)China Postdoctoral Science Foundation (Grant No. 2018M631104)the Guizhou Provincial Science and Technology Foundation (20171078)the Guizhou Institute of Technology Foundation (XJGC20130901)
文摘Partitioning behavior between amphibole and silicate glass of thirty-three minor and trace elements(Sc,Ti, V, Cr, Co, Rb, Sr, P, Y, Zr, Nb, Cs, Ba, K, La, Ce, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb,Th, and U) have been determined experimentally. Products of crystallization of hydrous basalt melts from 0.6 GPa/860 °C up to 2.6 GPa/970 °C were obtained in a multianvil apparatus. Major and trace element compositions of amphibole and glass were determined with a combination of electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The main mineral phase is calcic amphibole, and the coexisting glass compositions are tonalite, granodiorite, and granite. The compatibility of rare earth elements increase at 915 °C and then decrease at 970 °C, but the compatibility of most of these elements shows a continued, significant increase with increasing pressure. For high-field strength elements, large ion lithophile elements, actinide compatibility decrease with increasing temperature or pressure, but transition metals show a continued increase in compatibility within the temperature–pressure conditions. From mathematical and graphical fitting, we determined best-fit values for the ideal ionic radius(r_0, 1.01–1.04 ?), the strain-free partitioncoefficient(D_0, 1.18–1.58), and apparent Young's modulus(E, 142–370 GPa) for the M4 site in amphibole according to the lattice strain model. The D_0^(M4) for rare earth elements rises at 915 °C and then drops at 970 °C at 0.6 GPa.However, the D_0^(M4) values are positively proportional to the pressure for rare earth elements in the amphibole-glass pairs at 0.6–2.6 GPa and 970 °C. Furthermore, the derived best-fit values for r_0^(M4) and E^(M4) are almost constant and trend to increase with rising temperature and pressure,respectively. The partition coefficient is distinctly different for different melt compositions. The rare earth elements become more enriched in amphibole if the quenched glass is granodiorite or granite compared to the tonalitic glasses.
文摘Pasveh gabbros are mafic component of a plutonic complex in the northwest Sanandaj- Sirjan Zone. These cumulative rocks are composed of plagioclase and calcic clinopyroxene （Cpx）, which yield unusually high CaO （〉19 wt.%） in whole-rock chemistry. Petrographical and geochemical data suggest that Pasveh gabbros can be divided into two groups： free scapolite and scapolite-bearing gabbros. The second group has higher Na20, K20, and P205 relative to free scapolite ones and is enriched in LIL （large ion lithophile） and HFS （high field strength） elements. Two stages of metasomatism affected the primary composition of mafic rocks. Firstly, high temperature reaction caused to invert primary high Ti clinopyroxene to low Ti cUnopyroxene＋high Ti amphibole. This reaction was extensive and included all gabbroic samples. Hydrothermal fluids involved in this process can be derived from dehydration reactions of country rocks or from other magmas incorporated in the formation of Pasveh complex pluton. The second metasomatic stage relates to scapolitization of limited parts of gabbroic rocks. An external saline fluid, which is composed of major NaCI and minor KCI and P205 components, impacted locally on Pasveh gabbros and formed the second metasomatic stage. Possible sources of Na and Cl are primary evaporites or brines, which were present in the host sediments of the gabbros. The carbonate-free nature of these hydrothermal fluids suggests that hydrothermal fluids responsible for the formation of scapolite in Pasveh gabbros are derived from marine evaporitic parentage.
文摘Over a 70-year period, a mine near Libby, MT supplied nearly 80% of the world’s vermiculite. Raw vermiculite, which was contaminated with naturally occurring amphibole in veins throughout the deposit, was shipped to processing sites throughout the United States for exfoliation. In this pilot study, tree bark samples were collected near processing facilities in Spokane, WA, Santa Ana, CA, Newark, CA, and Phoenix, AZ in an effort to determine if areas surrounding these facilities are today contaminated with Libby amphibole asbestos (AA). From areas surrounding each of the four historical processing sites, Libby AA was detected in a subset of the bark samples. At the Santa Ana, Newark and Phoenix facilities, actinolite-tremolite and other high Fe Ca-bearing amphibole were also measured from the bark samples. In addition, chrysotile was frequently measured in samples collected from each of the sites. From the results of this pilot study, it is evident that tree bark can serve as reservoirs of asbestos, and indicators of past and current contamination. These data also suggest that areas outside of these historical processing facilities may today have some level of existing contamination resulting from the operation of these facilities.
基金financial support of the Analisi delle proprietàmicrostrutturali,chimico-fisiche di materiali inorganicideterminazioni quantitative della composizione mineralogica di materiali naturali e delle proprietàtecniche dei materiali litici Laboratory funds,DISTAV,University of Genoa.
文摘Crocidolite,amosite,anthophyllite,tremolite,actinolite besides the chrysotile serpentine polymorph fall within the classification of asbestos,whose commercial use is banned,and environmental and human exposure levels regulated.However,the cited amphibole species can crystallise in asbestiform or non-asbestiform habit and therefore their morphological characterization has a key role in assessing a reliable asbestos hazard scenario.Furthermore,when a mechanical stress is applied to rocks containing pristine prismatic or acicular amphiboles,these phases can break,originating particles with dimensions and geometrical ratios that would label them as asbestos.Therefore,a normative and scientific crucial gap arise in the classification criteria of a particle as a real asbestiform mineral or as a cleavage fragment(i.e.non-asbestos).The mode of comminution is fundamental for the following quantitative determination of fibres.It is critical because it can affect the morphology and geometric ratios of fibres,inducing positive or negative falses.In this framework,our work was focused on the Scanning Electron Microscopy coupled with Energy Dispersive Spettroscopy(SEM-EDS)analysis of amphiboles with asbestiform and non-asbestiform habit,subject to mechanical stress for three different time intervals,in order to assess how different time lengths of comminution control geometry and morphology of the particles.
