The Lanthanide Tetrad Effect in Argillic Alteration: An Example from the Jizvan District, Northern Iran

Intrusion of quartz-monzodioritic igneous bodies of Oligocene age into Eocene lithic crystal tufts and trachy-basalts resulted in the occurrence of a widespread argillic alteration zone in the Jizvan district （northern Iran）. Mineralogically, the argillie alteration zone includes minerals such as kaolinite, quartz, smectite, pyrophyllite, muscovite-illite, alunite, rutile, calcite, feldspar, chlorite, hematite and goethite. Therefore, the non-CHARAC behaviour for trace elements in the argillic samples is reflected in the non-chondritic Y/Ho and Zr/Hf ratios and the irregular REE patterns, which appear related to the tetrad effect phenomenon. The chondrite-normalized REE distribution patterns indicate both concave （W-shaped） and convex （M-shaped） tetrad effects in the argillic samples. Based on the field evidence and the results from geochemical studies, it can be concluded that the samples from the argillic alteration zone having high fourth tetrad effect values （〉0.30） were developed in the fault and breccia zones. The results indicate that factors such as preferential scavenging by Mn-oxides, crystallization of clay minerals, fluid-rock interaction, overprint of hypogene mineral assemblage by supergene ones, and the structural control, have all played an important role in the occurrence of tetrad effects in samples of the argillic zone in the Jizvan district.

REE Tetrad Effect as a Powerful Indicator of Formation Conditions of Karst Bauxites: A Case Study of the Shahindezh Deposit, NW Iran

Study of the concentration of major,trace,and rare earth elements(REE)in the Shahindezh karst bauxite deposit,northwestern Iran clarifies the relationship of the tetrad effect with geochemical parameters in the bauxite ores.The existence of irregular curves in the chondrite-normalized REE patterns as well as non-CHARAC behavior of geochemically isovalent pairs(Y/Ho)are related to the tetrad effect.The meaningful positive correlation between the sizes of the calculated T3 tetrad effect and some geochemical factors such as Y/Ho,ΣREE,La/Y,(La/Yb)N,and(LREE/HREE)N as well as some major oxides-based parameters like Al2O3+LOI/SiO2+Fe2O3,Al2O3/Fe2O3,Al2O3+LOI,IOL,and SiO2+Fe2O3indicate that the studied bauxite horizon was likely deposited by different(acidic and/or alkalic)solutions at different stages.The lower part of the studied horizon with a thickness of^4.7 m displays alkali characteristics whereas the upper parts of the horizon with a thickness of^5.3 m are characterized by more acidic conditions.These results are fully supported by the co-occurrence of convex-concave tetrad effect curves in the chondrite-normalized REE patterns.Therefore,the tetrad effect phenomenon used in this study has proved to be a good and reliable geochemical proxy to assess the conditions of the depositional environment in the Shahindezh bauxite ores.

Petrology, REE Geochemistry and Tetrad Effect of Some Muscovite Granites at Wadi El Gemal Area, South Eastern Desert, Egypt

The muscovite granites at the study area are being emplaced into biotite granites and ophiolitic mélange settings. They occur in four exposures namely;Umm Seleimat, Sikait, Umm El Kheran and Umm Addebaa exposure. The presence of garnet and muscovite flakes may reflect the peraluminous nature of the studied muscovite granites. Petrographically, the studied granites are mostly subsolvus and consist of plagioclase, K-feldspars, quartz, muscovite and biotite. Garnet, zircon, allanite and opaques are accessories. The textural features of these granites are expressed by bent plagioclase lamellae, distorted microcline twinning, deformed mica flakes and development of myrmekite and recrystallization of feldspars into fine-grained aggregates. Umm Seleimat and Sikait exposures are more differentiated due to the presence of high content of K-feldspar and LREEs. The REE budget decreased from Umm Seleimat-Sikait exposures to Umm El Kheran-Umm Addebaa exposures as (514.5 - 495.6) to (195.9 - 197.7), respectively. Umm Seleimat-Sikait exposures have lower HREE/LREE (0.12 - 0.67), relative to Umm El Kheran-Umm Addebaa exposures (0.99 - 2.06). The studied granites revealed that the chondrite normalized REE patterns are the normal M-type of tetrad effect, where TE1,3 tetrad effect is higher than 1 in all samples which implies that there was an interaction between melt and water-haloid-rich fluid when these granites are crystallized from magma. Spectrometric values of Umm Seleimat and Umm Addebaa indicate that U content is more than Th content. Applying the U mobilization equation proved that the studied granites have been originated from a late magmatic phase of magma very rich in radioelements, also the majority of measurements lie above the zero line indicating that the studied granites affected with hydrothermal solutions rich in uranium than thorium which indicates uranium addition.

Theoretical probe into universal tetrad effect for complexation discrepancy between lanthanide elements and organophosphoric extractant diethyl phosphoric acid

The deep understanding of 4f-correlated electron motion behavior is experimentally limited due to similar physicochemical properties of rare earth elements(REEs).While the solvent extraction behavior originating from the continuous occupation of 4f electrons along the lanthanide family provides a particular platform to probe the 4f electrons motion behavior and its correlations to their versatile functions.Herein,the complexation between REEs and the prototypical extractant of diethyl phosphoric acid(DEP)was substantially studied based on quantum mechanical calculation.The results firstly show that the average bond lengths between Ln and six coordinated oxygen atoms are consistent with lanthanide contraction phenomenon,and gadolinium break effect is also obviously observed.Secondly,the"tetrad effect"is figured out based on the subtle discrepancy of 4f electrons occupation,namely La-Nd,Sm-Eu,Gd-Dy and Ho-Lu.Specifically,the main composition is 4f5d6p for La-Nd,while the discrepancy is due to the increasing electrons in the 5d shell,while it is 4f5d for Pm-Eu.For Gd-Dy,their 4f orbitals accept little electrons and the donating electrons flow into 6s5d subshells due to the half-filled stability and the enhancement of shielding effect.The electrons donate into 5d6p subshells due to multiply electrons occupation of 4f orbitals for Ho-Lu.These detailed analyses obviously clarify the"tetrad effect"along the lanthanide family due to the different variation of 4f orbital occupation.It is expected that these microscopic understandings provide important guidance for the separation of REEs and the design of new extractants.

Geochemical Characteristics of Rare Earth Elements of Guidong Granitic Complex and Their Relationship with Uranium Mineralization

The Guidong granitic complex is constituted by Luxi pluton, Xiazhuang pluton, Maofeng pluton, Sundong pluton, Aizi pluton and Siqian pluton, which intruded in Indosinian and early Yanshanian Periods. These plutons varies from each other not only in major element content, aluminium saturation index, but also in ∑REE, δEu, and LREE/HREE, （La/Yb）N, （La/Sm） N and （Gd/Yb） N ratios. Uranium mineralization is mainly hosted by strong peraluminous granites, which has undergone intense fluid-rock interaction, and their REE compositions are characterised by M-type tetrad effects and lower ∑REE, δEu value, LREE/HREE, （La/Yb） N, （La/Sm） N and （Gd/Yb） N ratios.

Geochemical Characteristics of Rare Earth Elements of Guidong Granitic Complex and Relationship with Uranium Mineralization

Guidong granitic complex is constituted by Luxi intrusion, Xiazhuang intrusion, Maofeng intrusion, Sundong intrusion, Aizi intrusion and Siqian intrusion, which emplaced in Indosinian and early Yanshanian Periods. These intrusions varied from each other not only in major element content, aluminium saturation index, but also in values of ∑REE, δEu, and LREE/HREE, (La/Yb)N, (La/Sm)N and (Gd/Yb)N. The Maofeng intrusion, which has the closest relationship with uranium mineralization, belongs to strong peraluminous granites. Having undergone much intense fluid-rock interaction, it is characterized by typical M-type tetrad effects and lowest values of ∑REE, δEu, LREE/HREE, (La/Yb)N, (La/Sm)N and (Gd/Yb)N ratios than other studied intrusions.

Fractionation of Rare Earth Elements in Plants Ⅰ. Fractionation Patterns and Their Forming Mechanisms in Different Organs of Triticum Aestivum

Fractionations of rare earth elements (REEs) and the forming mechanisms in plants were studied using Triticum aestivum as plant material with application of exogenous REEs and hydroponic culture. REEs were significantly fractionated in different parts of Triticum aestivum. M-type tetrad effect could be observed in both root and shoot of Triticum aestivum, which might result from the different abilities of REEs to form phosphate precipitation. Middle REEs (MREEs), light REEs (LREEs) and heavy REEs (HREEs) were enriched in root, stem and leaf of Triticum aestivum, respectively. REE speciation calculations using VMINTEQ program show REEs in simulated xylem solution mainly exist as REE-EDTA^(- )and RE^(3+), but only HREEs are enriched in REE-EDTA^(-), while LREEs are enriched in the other REE species. It is suggested that the fractionation between LREEs and HREEs might be caused by the uptake of REE-EDTA^(-) in Triticum aestivum leaves, but might result from the uptake of the other REE species in their stems.

Geochemistry, Geochronology and Lu-Hf Isotopes of Peraluminous Granitic Porphyry from the Walegen Au Deposit, West Qinling Terrane

Walegen Au deposit is closely correlated with granitic intrusions of Triassic age, which are composed of granite and quartz porphyries. Both granite porphyry and quartz porphyry consist of quartz, feldspar and muscovite as primary minerals. WeaMy peraluminous granite porphyry （A/ CNK=1.10-1.15） is enriched in LREE, depleted in HREE with Nb-Ta-Ti anomalies, and displays subduction-related geochemistry. Quartz porphyry is strongly peraluminous （A/CNK=1.64-2.81） with highly evolved components, characterized by lower TiO2, REE contents, Mg#, K/Rb, Nb/Ta, Zr/Hf ratios and higher Rb/Sr ratios than the granite porphyry. REE patterns of quartz porphyry exhibit lanthanide tetrad effect, resulting from mineral fractionation or participation of fluids with enriched F and CI. LA- ICP-MS zircon U-Pb dating indicates quartz porphyry formed at 233±3 Ma. The ages of relict zircons from Triassic magmatic rocks match well with the detrital zircons from regional area. In addition, εHf（t） values of Triassic magmatic zircons from the granite and quartz porphyries are -14.2 to -9.1 （with an exception of ＋4.1） and -10.8 to -8.6 respectively, indicating a crustal-dominant source. Regionally, numerous Middle Triassic granitoids were previously reported to be formed under the consumption of Paleotethyan Ocean. These facts indicate that the granitic porphyries from Walegen Au deposit may have been formed in the processes of the closing of Paleotethyan Ocean, which could correlate with the arc-related magmatism in the Kunlun orogen to the west and the Qinling orogen to the east.

Geochemistry and Petrogenesis of Late Ediacaran Rare-metal Albite Granites of the Arabian-Nubian Shield

The Abu Dabbab albite granite(ADAG),in the central Eastern Desert of Egypt,hosts the most significant rare metal ore deposit in the northern part of the Neoproterozoic Arabian-Nubian Shield.Here,we report detailed field,petrographic,mineralogical and geochemical investigation of the ADAG,an isolated stock-like granitic body with sharp intrusive contacts against metamorphic country rocks,probably emplaced at about 600 Ma.The fine-grained porphyritic upper unit is a preserved remnant of the shallowly-emplaced apex of the magma chamber,whereas the medium-grained lower unit crystallized at deeper levels under subvolcanic conditions.The peraluminous leucocratic ADAG shares common geochemical characteristics with post-collisional intraplate A-type magmas.In addition to the conspicuous enrichment in Na2O,the ADAG is remarkable for its anomalous concentrations of Ta,Nb,Li,Hf,Ga,Sn,Zn and heavy rare-earth elements.Nb-Ta minerals in the ADAG are mixed with Fe-Mn oxides,forming black patches that increase in abundance toward of the base of the intrusion.Columbite-tantalite,cassiterite and wolframite are the most important ore minerals.Pronounced negative Eu anomalies(Eu/Eu*=0.10–0.24)reflect extreme magmatic fractionation and perhaps the effects of late fluid-rock interaction.The ADAG was most likely generated by partial melting of the juvenile middle crust of the ANS as the geotherm was elevated by erosional uplift following lithospheric delamination and it was emplaced at the intersection of lineations of structural weakness.Although formation of the ADAG and its primary enrichment in rare metals are essentially due to magmatic processes,late-stage metasomatism caused limited redistribution of rare metals.Fluid-driven subsolidus modification was limited to the apex of the magma chamber and drove development of greisen,amazonite,and quartz veins along fracture systems.

Study on Interaction Energy of PAMAM/Lanthanide(Ⅲ) by Molecular Dynamics Method

PAMAM/lanthanide （Ⅲ） nanocomposite was studied by molecular simulation method. Molecular simulation enabled study of the lanthanide tetrad effect at atomic level. However, PAMAM dendrimer exhibiting unique properties such as nanometer size and highly functionalized terminal surface provided a novel space for lanthanide （Ⅲ） to show their peculiar tetrad effect. The results showed that total energies of PAMAM/lanthanide（Ⅲ） nanocomposites presented obvious tetrad effect and special double-double effect. Nd, Gd, and Er fell to the lower point and Gd fell to the lowest point in the TE-Ln curve with four groups. In order to explain the tetrad effect, kinetic energy （KE） and potential energy （PE） were analyzed. The KE curve consisted of three W-type parts （La - Pm, Pm - Tb, Tb - Tm, and the latter two W-type part were axial symmetry） and an exception part （Yb - Lu）. It also showed that the KE of odd atomic number was higher than the even one＇s with exception of Yb and Lu. Furthermore, decomposed potential energies gave out the atomic-level subtle difference of lanthanide which present more regulations for Eu（Ⅲ） - Lu（Ⅲ） compared with La（Ⅲ） - Sm（Ⅲ）. And also Ho-valley and three platforms （Sm - Eu, Td - Dy, Er - Tm） were discovered that refect the regular change of nanocomposite structures. Additionally, there are distinct correlations between Ebond and EInversion, EAngle and EVDW, Eworsion and ECoul, respectively. Therefore, PAMAM could be used in separation of lanthanide by changing conditions.

Mineralogy and Geochemistry of Uraniferous Sandstones in Fault Zone,Wadi El Sahu Area,Southwestern Sinai,Egypt:Implications for Provenance,Weathering and Tectonic Setting

Paleozoic rocks in the Wadi El Sahu area are affected by many major faults in different directions.A reverse fault trending NE-SW is exposed for about 300 m of its length as it cuts through the Abu Hamata and Adedia formations on the south side of Wadi El Sahu.A secondary ascending hydrothermal solution carrying heavy metals and radioactive minerals passed through the fault plain and the surrounding fractures,forming mineralized and radioactive zone.The mineralized zone thickness ranges from 60 cm to 200 cm along the fault plain.These rocks were analyzed radiometrically using a portable gamma-ray spectrometer,chemically by employing ICP-ES and ICP-MS,as well as mineralogically by both binocular and Environmental Scanning Electron microscope.Gold content was also determined by fire assay.REE and U contents reached up to 2682 and 1216 ppm,respectively.Mineralogical investigations indicated the presence of uraninite,torbernite,autunite,sklodowskite,kasolite as uranium minerals,thorite as a thorium mineral,monazite,allanite and xenotime as REE-bearing minerals,zircon and columbite as accessory minerals,gold and nickel as precious and base metals,in addition to cassiterite,chalcopyrite,chalcocite and chrysocolla.High REE and U contents are attributed to the circulation of epigenetic U and REE-bearing hydrothermal solutions along the fault plain and its surrounding fractures.Hydrothermal alteration processes could then be confirmed by the presence of the M-type tetrad effect in the REE-patterns of the ferruginous sandstone.The non-chondritic ratio of Nb/Ta,Zr/Hf and Y/Ho in the studied sandstone may be attributed to the tetrad effect.The Ce and Eu anomaly with unusual REE-patterns was represented by the presence of conjugated M-W tetrad effects,indicating either the dual effect of hydrothermal solutions or groundwater with seawater.The results clarify that the tetrad-effects could be used as evidence for the environment of deposition and as an indication for gold mineralization.

Petrological and Geochemical Constraints on the Evolution of EI-Kahfa Alkaline Ring Complex, South Eastern Desert, Egypt

El-Kahfa complex locates at the intersection of Lat. 24°8′18″ N and Long. 34038′55″ E, South Eastern Desert of Egypt. It comprises an outer ring composed of alkaline syenites, ranging from barrento quartz-bearing syenites, an inner ring which varies in composition from leucocratic to melanocratic syenites, and a central stock formed essentially of alkali gabbros. These alkali gabbros are cut by small bodies of alkaline syenites, which occasionally grade into nepheline syenites. The country rocks are represented mainly by metavolcanics and epidiorites. El-Kahfa syenites lack any primary hydrous mafic silicates indicating that their magma was anhydrous. Major and trace elements geochemistry of EI-Kahfa rocks reflects the crystallization of early plagioclase followed by Fe-Ti oxides. Salic members in the complex are co-magmatic and related to crystal liquid fractionation. The REE （rare earth elements）＇s tetrad is obvious on the primitive mantle normalized pattern of El-Kahfa rocks. The M-type tetrads clearly appear in the more evolved rocks. These tetrad effects are either a feature of magma-fluid system before crystallization or inherited from external fluid during or after the emplacement of the magma. Generally, El-Kahfa rocks parental magma was probably derived from Nb-enriched or at least under-plate mantle source within the continental East-Africa rift zone, where it may be subjected to minor contamination through their fractional crystallization.

Paleocene A-type igneous suites in the Sikhote-Alin(the East Asian continental margin):Petrological,geochronological,isotopic,and geodynamic constraints

Global geodynamic reconstruction models of the Pacific margin of Asia refer to materials collected throughout Japan,Korea and northeastern China,but they lack data on southern Sikhote-Alin.Therewith,the Sikhote-Alin orogenic belt(NE Asia)constituted a single eastern margin of the paleo-Asian continent with the abovementioned territories in the Paleocene.New isotopic,geochemical,and geochronological data show that Paleocene igneous activity(-61-55 Ma)is widely developed in south-ern Sikhote-Alin.Bulk rock compositions of the igneous rocks of this period yield ferroan,peraluminous,calc-alkaline to alkaline affinities,highly abundant LILE and HFSE(with pronounced Ba,Sr,Eu,and Ti neg-ative anomalies)and depleted HREE.The initial melts,displaying Zr+Y+Ce+Nb>350 ppm and 10,000×Ga/Al>2.6,derived from an OIB-like mantle source crystallised under fairly reducing conditions(below FMQ buffer),and yield high temperature of zircon saturation(>850℃),indicating typical A-type granite and related volcanic rock features.It is logical to associate variations in A-type rock geochemical composition with an enrichment of the upper part of the magma chamber with fluid-mobile components involving a reditribution of major and trace elements through fluid-magmatic differentiation.Strong depletion in Ca,Mg,Ba,Sr,Eu in the A-type rocks is caused by an outflow of these elements by an oxi-dizing,initially reduced,acidic fluid beyond the zone of magma generation.Whole-rock Sr-Nd isotope data argue for the generation of the A-type rocks by melting of dominantly a juvenile mantle component with a subordinate component of the ancient crust.Isotope variations of igneous rocks of the reference area:^(87)Sr/^(86)Sr(t)(0.7024-0.7118),ε_(Nd)(t)(-0.9 to-5.1)and T_(DM2)(934-1277 Ma),result from the mixing of the OIB-like mantle source with selective melts or from the metapelite contamination of the Samarka terrane accretionary prism and of the Zhuravlevka-Amur turbidite basin,later followed by fluid-magmatic differentiation that led to the formation of anatectic or hybrid melts.We further suggest that the origin of the A-type granites and related volcanic rocks is the result of the oblique interaction of ocea-nic and continental plates.This interaction accounts for the simultaneous formation of tears in the slab,enabling sub-slab asthenospheric upwelling,and strike-slip fault-related extensional structures in the overriding continental plate.

Hydrothermal activities and seawater acidification in the Late Devonian F-F transition:Evidence from geochemistry of rare earth elements

Rare-earth dements （REE） in limestones were measured by ICP-MS from the Yangdi section across the Frasnian-Famennian （F-F） transition in Guilin, Guangxi of South China. The average EREE contents of measured samples are 33.32 ppm. The average LREE/HREE ratio is 6.35. Data show LREE-enriched REE distribution pattern in the Yangdi section. Most of samples are characterized by positive Eu anomaly with average of 1.13, and there are two maxima of Eu anomaly just below the F-F boundary. Almost all analytical samples show obvious tetrad effects. Remarkable M-shaped tetrad effects are observed in these samples with positive Eu anomaly. The characters of REE and some relative elements （Fe, Mn, Al, etc.） indicate that hydro- thermal activities occurred and resulted in seawater acidification in Upper and Lower Kellwasser horizons of the Late Devonian. The changes of marine environment caused by hydrothermal activities, such as seawater acidification, heavy metal pollution, and eutrophication, would destroy the neritic ecosystem and finally result in the F-F mass extinction.

Petrogenesis of early Yanshanian highly evolved granites in the Longyuanba area,southern Jiangxi Province:Evidence from zircon U-Pb dating,Hf-O isotope and whole-rock geochemistry

Early Yanshanian(Jurassic) granitoids are widespread in the Nanling Range,South China.Whereas large granitic batholiths commonly crop out in the center of the Nanling Range(corresponding geographically to the central and northern parts of Guangdong Province),many small stocks occur in the southern part of Jiangxi Province.Most of the small stocks are associated closely with economically significant rare-metal deposits(W,Sn,Nb,Ta).Here we report the results for biotite granites and two-mica granites from three Yanshanian stocks of the Longyuanba complex.LA-ICPMS U-Pb dating of zircon yields an age of 156.1±2.1 Ma for Xiaomubei biotite granite,and U-Pb zircon dating using SIMS yields an age of 156.7±1.2 Ma for Longyuanba-Chengjiang biotite granite and 156.4±1.3 Ma for Jiangtoudong two-mica granite.Biotite granites are silica-rich(SiO 2 =70%-79%),potassic(K 2 O/Na 2 O>1.9),and peraluminous(ASI=1.05-1.33).Associated samples are invariably enriched in Rb,Th,Pb and LREE,yet depleted in Ba,Nb,Sr,P and Ti,and their REE pattern shows a large fractionation between LREE and HREE((La/Yb) N =10.7-13.5) and a pronounced Eu negative anomaly(δEu=0.28-0.41).Two-mica granite samples are also silica-rich(SiO 2 =75%-79%),potassic(K 2 O/Na 2 O>1.2),and peraluminous(ASI=1.09-1.17).However,in contrast to the biotite granites,they are more enriched in Rb,Th,Pb and extremely depleted in Ba,Nb,Sr,P and Ti,and exhibit nearly flat((La/Yb) N =0.75-1.08) chondrite-normalized REE patterns characterized by strong Eu depletion(δEu=0.02-0.04) and clear tetrad effect(TE 1.3 =1.10-1.14).Biotite granites and two-mica granties have comparable Nd isotopic signatures,and their εNd(t) are concentrated in the 13.0 to 9.6 and 11.5 to 7.7 respectively.Their zircon Hf-O isotopes of both also show similarity(biotite granites:εHf(t)= 10.8-7.9,δ 18 O=7.98‰-8.89‰ and εHf(t)= 13.8 to 9.1,δ 18 O=8.31‰-10.08‰;two-mica granites:εHf(t)= 11.3 to 8.0,δ 18 O=7.91‰-9.77‰).The results show that both biotite and two-mica granites were derived mainly from sedimentary source rocks with a minor contribution from mantle-derived materials.In spite of some S-type characteristics,the biotite granites were formed by fractional crystallization of I-type magma and assimilation of peraluminous sedimentary rocks during their ascent to the surface.Therefore,they belong to highly fractionated I-type granites.Two-mica granites exhibit a tetrad effect in their REE patterns,but share the same isotopic features with the biotite granites,suggesting that they are highly fractionated I-type granites as well.Their Lanthanide tetrad effects may be attributed to the hydrothermal alteration by magmatic fluids that have suffered degassing at late stages.Granitic magmas undergoing fractional crystallization and wall-rock assilimation can generate highly evolved granites with no REE tetrad effect in the uni-phase system.However,in the late-stage of magmatic evolution in the multi-phase system(i.e.,magmatic-hydrothermal system),these magmas also can lead to the highly evolved granites exhibiting mew-shaped REE pattern characterized by tetrad effect as the consequence of melt-fluid and fluid-vapor fractionation,and the resultant autometasomatism.We thus suggest that the REE pattern exhibiting tetrad effect feature is an important indicator of rare metal mineralization in the early Yanshanian time in southern China,implying the metamorphism of the ore fluid.

Magmatic Evolution of Garnet-Bearing highly Fractionated Granitic Rocks from Macao,Southeast China:Implications for Granite-Related Mineralization Processes

The widespread W-(Mo)-Sn-Nb-Ta polymetallic mineralization in Southeast(SE)China is genetically associated with Mesozoic highly fractionated granitic rocks.Such rocks have enigmatic mineralogical and geochemical features,making its petrogenesis an intensely debated topic.To better understand the underlying magma evolution processes,petrography,garnet chemistry and whole-rock major and trace element data are reported for Jurassic highly fractionated granitic rocks and associated microgranite and aplitepegmatite dikes from Macao and compared with coeval similar granitic rocks from nearby areas in SE China.Despite the fact that the most evolved rocks in Macao are garnet-bearing aplite-pegmatite dikes,the existence of coeval two-mica and garnet-bearing biotite and muscovite granites displaying more evolved compositions(e.g.,lower Zr/Hf ratios)indicates that the differentiation sequence reached higher degrees of fractionation at a regional scale.Although crystal fractionation played an important role,late-stage fluid/melt interactions,involving F-rich fluids,imparted specific geochemical characteristics to Macao and SE China highly fractionated granitic rocks such as the non-CHARAC(CHArge-and-RAdius-Controlled)behavior of trace elements,leading,for example,to non-chondritic Zr/Hf ratios,Rare Earth Elements(REE)tetrad effects and Nb-Ta enrichment and fractionation.Such process contributed to the late-stage crystallization of accessory phases only found in these highly evolved facies.Among the latter,two populations of garnet were identified in MGI(Macao GroupⅠ)highly fractionated granitic rocks:small grossular-poor euhedral grains and large grossular-rich skeletal garnet grains with quartz inclusions.The first group was mainly formed through precipitation from highly evolved Mn-rich slightly peraluminous melts under low-pressure and relatively low temperature(~700℃)conditions.Assimilation of upper crust metasedimentary materials may have contributed as a source of Mn and Al to the formation of garnet.The second group has a metasomatic origin related to the interaction of magmatic fluids with previously crystallized mineral phases and,possibly,with assimilated metasedimentary enclaves or surrounding metasedimentary strata.The highly fractionated granitic rocks in Macao represent the first stage in the development of granite-related W-(Mo)-Sn-Nb-Ta mineralization associated with coeval more evolved lithotypes in SE China.