The Weixi High-silica Granitoids in the Central Sanjiang Orogenic Belt,Southwest China:Implications for Growth of the Continental Crust

High-silica granitoids record the formation and evolution of the continental crust.A new intrusive complex has been recognized among silicic volcanic rocks of the Weixi arc,Southwest China.The intrusions consist of granites,granitic porphyries,and granodiorites.Zircon U-Pb age data indicate that the Weixi granitoids formed at 248-240 Ma and were coeval with silicic volcanic rocks of the Weixi arc.The Weixi granitoids are enriched in Rb,Th,and U,depleted in Ba,Sr,Nb,Ta,and Ti,and have high light/heavy rare earth element ratios and slightly negative Eu anomalies.The Weixi granitoids have negative ε_(Nd)(t)values(-9.8 to-7.8)and negative zircon ε_(Hf)(t)values(-12.02 to-5.11).The geochemical and isotopic features suggest the Weixi granitoids were derived by partial melting of ancient crustal material.The Weixi granitoids and silicic volcanic rocks were derived from the same magma by crystal accumulation and melt extraction,respectively,and they record the formation of a continental arc in the central Sanjiang orogenic belt.

Petrogenesis of Oligocene Granitoids and its Implications on Beryllium Mineralization at Pagele,Nianqingtanggula Mountain(Central Tibet)

The newly discovered Oligocene granitoids(33.1-28.7 Ma)at Pagele are magmatic rocks related to beryllium mineralization during the India-Asia late-collisional stage.This discovery provides an ideal example to study the latecollisional orogeny and beryllium prospecting in the Lhasa terrane.The Oligocene granitoids include porphyritic granodiorite,StageⅠ,ⅡandⅢgranites,and granitic pegmatite.Geochemical analysis shows that the porphyritic granodiorite is characterized by high SiO_(2),K_(2)O,totalΣREE contents,and(La/Yb)N ratios;while the latter two by higher SiO_(2),lowerΣREE and(La/Yb)N ratios.Notably,the granitic pegmatite has extremely high Y/Ho,low K/Rb and Zr/Hf,and distinct REE tetrad effect(1.14-1.21).This study suggests that the porphyritic granodiorite may be derived from partial melting of beryllium-rich materials composed of Lhasa ancient crust(70%-80%)and enriched Lhasa lithospheric mantle(20%-30%)under the tearing subduction of Indian slab.The three-stage granites and granitic pegmatite,which contain higher beryllium contents or beryls,were likely generated by highly fractionation of the porphyritic granodioritic magma or other homologous magma.Considering the possible genetic and spatial link between Indian slab tear and rifts,we suggest that highly-fractionated granites in rifting systems represent important Be prospecting targets in the Lhasa terrane.

Petrogenesis and tectonic implications of the Silurian adakitic granitoids in the eastern segment of the Qilian Orogenic Belt,Northwest China

Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.

Magma Mixing Genesis of the Mafic Enclaves and Related Granitoids in the Kan Granite-Gneiss Complex of Central Côte d’Ivoire: Evidence from Geology, Petrology and Geochemistry

The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.

The Origin of Mesozoic A-type Granitoids,Fujian Province,Southeast China:Insights from Geochronology,Mineralogy and Geochemistry

The magma sources,origins and precise forming ages of the miarolite from Qishan and Kuiqi intrusions are still uncertain.New results reveal that,miarolites from the Qishan and Kuiqi intrusions yield crystallization ages of~101 and~98 Ma,and they have a high formation temperature(~910℃)and low oxygen fugacity value,indicating crystallization condition at low pressure in the upper crust with temperature of 678℃.The Qishan and Kuiqi miarolites are characterized by enrichment in SiO_(2) and high-K alkali,depletion in Ca and Mg,and belong to the high-K weak peraluminous rock series.The samples are enriched in HFSEs(i.e.,Ta,Zr and Hf)and LILEs(i.e.,Ba,P and Sr),depleted in Ba and Sr with the negative anomaly of Eu.In the primitive mantle normalized trace element spider diagram,the samples show a right-inclined‘seagull-type’pattern,combined the ratios of(La/Yb)_(N),10000×Al/Ga,Rb/Nb and Nb/Ta etc.,they were proved to be alkaline A-type granite.Combined the characterize of the trace elements,they were derived from clay-rich source accompanied pelite melting,and subjected to K-feldspar crystallization fractional.The values of ε_(Hf)(t)and tDM2 are distributed in the range of-2.8 to 3.3 with~1.2 Ga,and-6.0 to 4.0 with~1.2 Ga,revealing that they were generated from the Mesoproterozoic Cathaysia basement rocks.The comprehensive research reveals the Kuiqi and Qishan intrusions derived from crust-mantle mixing and partial melting of the crust,respectively,resulting from lithospheric extension generated by the Paleo-Pacific Plate subducted into the European-Asian Plate.

Investigation of Groundwater Quality with Borehole Depth in the Basin Granitoids of the Ashanti Region of Ghana

The dependence of groundwater quality on borehole depth is usually debatable in groundwater studies, especially in complex geological formations where aquifer characteristics vary spatially with depth. This study therefore seeks to investigate the relationship between borehole depth and groundwater quality across the granitoid aquifers within the Birimian Supergroup in the Ashanti Region. Physicochemical analysis records of groundwater quality data were collected from 23 boreholes of public and private institutions in the Ashanti Region of Ghana, and the parametric values of iron, fluoride, total hardness, pH, nitrate, and nitrite were used to study the groundwater quality-depth relationship. The results showed that the depth-to-groundwater quality indicated a marginal increase in water quality in the range of 30 to 50 m, which is mathematically represented by the low-value correlation coefficient (r2 = 0.026). A relatively significant increase occurs in the depth range of 50 to 80 m, which is given by a correlation coefficient of r2 = 0.298. The mean percent parameter compatibility was 74%, 82%, 89%, and 97% at 50, 60, 70, and 80 m depths, respectively. The variations in groundwater quality per depth ratio ranged from 1.48, 1.37, 1.27, and 1.21 for 50, 60, 70, and 80 m depth, respectively. The recommended minimum borehole depth for excellent groundwater quality is suggested with a compatibility per meter depth ratio of 1.37. This results in a range between 50 and 70 m as the most desirable drilling depth for excellent groundwater quality within the granitoids of the Birimian Supergroup of the Ashanti Region in Ghana.

Zircon U-Pb geochronology,Hf isotopes,and geochemistry constraints on the age and tectonic affinity of the basement granitoids from the Qiongdongnan Basin,northern South China Sea

Studies in the northern South China Sea(SCS)basement remain important for understanding the evolution of the Southeast Asian continental margin.Due to a thick cover of sediments and scarce borehole penetration,little is known about the age and tectonic affinity of this basement.In this study,an integrated study of zircon U-Pb geochronology,Hf isotopes,and whole-rock major and trace elements on seven basement granitoids from seven boreholes of Qiongdongnan Basin has been carried out.New zircon U-Pb results for these granitoids present middle-late Permian((270.0±1.2)Ma;(253±3.4)Ma),middle to late Triassic((246.2±3.4)Ma;(239.3±0.96)Ma;(237.9±0.99)Ma;(228.9±1.0)Ma)and Late Cretaceous ages((120.6±0.6)Ma).New data from this study,in combination with the previous dataset,indicates that granitoid ages in northern SCS basement vary from 270 Ma to 70.5 Ma,with three age groups of 270–196 Ma,162–142 Ma,and 137–71 Ma,respectively.Except for the late Paleozoic-Mesozoic rocks in the basement of the northern SCS,a few old zircon grains with the age of(2708.1±17)Ma to(2166.6±19)Ma provide clues to the existence of the pre-Proterozoic components.The geochemical signatures indicate that the middle Permian-early Cretaceous granitoids from the Qiongdongnan Basin are I-type granites formed in a volcanic arc environment,which were probably related to the subduction of the Paleo-Pacific Plate.

Petrological and Geochemical Constraints on the Origin of Strongly Peraluminous Granitoids from the Triassic Guangtoushan Pluton in South Qinling

As an important part of the early Mesozoic granites in the South Qinling tectonic belt(SQTB),the Guangtoushan pluton provides a material basis for research on the composition of magma sources and the effects of peritectic assemblage entrainment(PAE)on the changes in the granite composition.As shown by the results of LA-ICP-MS zircon U-Pb dating,the Guangtoushan pluton was emplaced during the Late Triassic(214-212 Ma)and was formed in the post-collision stage between the SQTB and the Yangtze plate.The collected samples had high SiO_(2)content and low Cr and Ni contents,indicating that the magmas did not undergo significant crust-mantle mixing during their evolution.The Guangtoushan granitoids were distributed along the trend line of magmatic fractional crystallization in the F-An-Or diagram.This result,combined with the relatively homogeneous Sr-Nd isotopic composition,implies that the Guangtoushan pluton underwent slight assimilation and contamination.As can be inferred from the comparison between the compositions of the Guangtoushan granitoids and various fluid-absent experimental melts,the magma sources of the Guangtoushan granitoids contain a variety of materials,such as graywackes,pyroclastic graywackes,and pelites and are not derived from lower crustal mafic rocks.The correlation between the maficity and the major and trace elements further indicates that the strongly peraluminous granitoids from the Guangtoushan pluton was formed by the partial melting of biotite-bearing crustal rocks and its magmatic evolution was accompanied by the entrainment of clinopyroxenes and accessory minerals.

Litho-Structural and Geochemistry Analysis of Granitoids from Mount Fouimba and Goma in Seguela Area (Central-Western Côte d’Ivoire)

The petrogeochemical analysis of the granitoids of Mount Fouimba and Mount Goma in the Seguela region (central-western C?te d’Ivoire) is the subject of this study. This analysis combines remote sensing, geophysics, petrography and geochemistry, in order to determine the major characteristics of the granitoids in the study area, and above all to participate in the detailed mapping of all the Ivorian terrains. The granitoids encountered in this region are essentially two-mica granites, granodiorites and porphyry basalts. Chemical analysis indicates that these granitoids are of the ferrous and magnesian type with peraluminous to weakly metaluminous characteristics. They originate from the mantle and were emplaced in an active continental margin context.

Petrology, Age and Geodynamic Implication of the Panafrican Granitoids Associated with the Glito-Kpatala Shear Zone (South-East Togo)

The granitic plutons associated with the Glito-Kpatala shear zone are composed of biotite and amphibole granodiorites, biotite granites, two-mica granites and aplitic granites, which are very poorly represented. The chemical and mineralogical compositions of these facies indicate that they are I type and belong to high-K calc-alkaline series, with a chemical metaluminous character displayed by the granodiorites relative to the biotite and two-mica facies whose chemical compositions vary between metaluminous and peraluminous caracter. The Th/Ta (14.04 - 43.82 ppm, mean = 26.05), Th/U (2.58 to 15.05 ppm, mean = 5.85 ppm), Zr/Hf (25.27 to 37.21, mean = 30.67 ppm) and Rb/Sr (0.16 to 4.32;mean = 1.67 ppm) ratios of these granitoids reveal a strong crustal involvement in their magmatogenesis. Variations in CaO/Na2O (0.47 - 1.44 ppm), Rb/Sr (0.14 - 0.27 ppm), Rb/Ba (0.07 - 0.14 ppm) and Sr/Y (38.21 - 174.42 ppm) ratios indicate that biotite and amphibole granodiorites with their excessive Ni (135.37 - 139.51 ppm) and Cr (395.73 - 447.74 ppm) were derived from a mafic to intermediate lower continental crust where garnet and/or amphibole were stable residual assemblage minerals. The moderate Sr/Y ratios (1.81 - 9.47 ppm) and low transition elements Ni (1 - 6.44 ppm) and Cr (7.89 - 13.47 ppm) contents in both the two-mica and biotite granites are consistent with their emplacement at relatively shallow depths in the upper to mean continental crust, at pressures below 10 Kbar. In the two-mica granites, moderate CaO/Na2O (0.20 - 0.57 ppm, mean = 0.38 ppm) and Rb/Ba (0.39 - 1.37, mean = 0.84 ppm) ratios and quite varied Rb/Sr (1.53 - 4.23 ppm, mean = 2.85 ppm) ratios indicate a predominant derivation from psammitic and pelitic metasediments rather than metagreywackes. These low ratios (0.25 ≤ CaO/Na2O ≤ 0.32, mean = 0.28 ppm;0.31 ≤ Rb/Ba ≤ 0.44, mean = 0.39 ppm;1.11 ≤ Rb/Sr ≤ 1.78, mean = 0.39 ppm) in biotite granites are more consistent with melting from a metagreywacke-derived source. Evidence for the contribution of mantle-derived mafic magma with granitic magma in the plutons studied is materialized by the presence of magmatic enclaves in both granodiorites and two-mica granites, the volcanic arc geochemical signatures displayed by the plutons in geotectonic diagrams and Nb/Ta ratios (14.14 - 34.61 ppm) closer to mantle estimates. Geochemical data and radiometric dating elements suggest that the granitoids studied can be integrated into the pan-African late magmatic episode, which corresponds between 606 and 583 Ma, to the activity of transcurrent ductile strike-slips and to the synchronous emplacement of high K calc-alkaline plutons in a post-collisional context.

Paleoproterozoic Granitoids on Liaodong Peninsula, North China Craton

Paleoproterozoic granitoids are an important constituent of the Jiao-Liao-Ji Belt(JLJB). The spatial-temporal distribution and types of Paleoproterozoic granitoids are closely related to the evolution of the JLJB. In this paper, we review the field occurrence, petrography, geochronology, and geochemistry of Paleoproterozoic granitoids on Liaodong Peninsula, northeast China. The Paleoproterozoic granitoids can be divided into pre-tectonic(~2.15 Ga;peak age=2.18 Ga) and post-tectonic(~1.85 Ga) granitoids. The pre-tectonic granitoids are magnetite and hornblende-biotite monzogranites and granodiorites. Pre-tectonic monzogranites are widespread in the JLJB and have A2-type affinities. In contrast, pretectonic granodiorites are only present in the Simenzi area and have adakitic affinities. The post-tectonic granitoids consist of porphyritic monzogranite, syenite, diorite, granodiorite, quartz monzonite, monzogranite, and granitic pegmatite, which are adakitic rocks and I-, S-, and A2-type granitoids. The assemblage of pre-tectonic A2-type granitoids and adakitic rocks indicates the initial tectonic setting of the JLJB was a continental back-arc basin. The assemblage of post-tectonic adakitic rocks and I-, S-, and A2-type granitoids indicates a post-collisional setting. The 2.20-2.15 Ga A2-type granitoids and adakitic rocks were associated with the initial stage of back-arc extension, and the peak of back-arc extension is inferred from the subsequent(2.15-2.10 Ga) mafic intrusive activity. The ~1.90 Ga adakitic rocks mark the beginning of the postcollisional stage, which was followed by the intrusion of low-temperature S-and I-type granitoids. High-to low-pressure granitoids(S-type) were generated during the peak of post-collisional lithospheric delamination and asthenospheric upwelling. The emplacement of later granitic pegmatites occurred during the waning of the orogeny.

Metallogenesis related to Mesozoic Granitoids in the Nanling Range, South China and Their Geodynamic Settings

Affected by the compressive stress from the South-Central （Indo-China） Peninsula, the Indosinian orogenesis, characterized by collision, thrust and uplifting, took place inside the South China Plate during 250-230 Ma. The ages of the Indosinian granitoids in the Nanling Range and vicinity areas are mostly 240-205 Ma, indicating that they were emplaced in both late collision and post-collision geodynamic environments. No important granite-related metallogenesis occurred in this duration. A post-orogenic setting started at the beginning of the Yanshanian Period, which controlled large-scale granitic magmatism and related metallogenesis. This paper makes the first attempt to divide the Yanshanian Period into three sub-periods, i.e. the early, middle and late Yanshanian Periods, based mainly on the features of magmatism, especially granitoids and related metallogenesis and their geodynamic environments. The magmatic association of the Early Yanshanian （about 185-170 Ma） comprises four categories of magmatism, i.e. basalt, bimodal volcanics, A-type granite and intraplate high-K calc-alkaline （HKCA） magmatism, which indicates an extension-thinning of lithosphere and upwelling of mantle material to a relative small and local extent. Pb-Zn, Cu and Au mineralizations associated with HKCA magmatism represents the first high tide of Mesozoic metallogenesis in the Nanling Range area. During the middle Yanshanian, the lithosphere was subjected to more extensive and intensive extending and thinning, and hence mantle upwelling and basaltic magma underplating caused a great amount of crust remelting granitoids. This period can be further divided into two stages. The first stage （170-150 Ma） is represented by large-scale emplacement of crust remelting granites with local tungsten mineralization at its end. The second stage （150-140 Ma） is the most important time of large-scale mineralizations of non-ferrous and rare metals, e.g. W, Sn, Nb-Ta, Bi, Mo, Be, in the Nanling Range area. The late Yanshanian （140-65 Ma） was generally characterized by full extension and breakup of the lithosphere of South China. However, owing to the influence of the Pacific Plate movement, the eastern part of South China was predominated by subduction-related compression, which resulted in magmatism of calc-alkaline and shoshonite series and related metallogeneses of Au, Ag, Pb-Zn, Cu and （Mo, Sn）, followed by extension in its late stage. In the Nanling Range area, the late Yanshanian magmatism was represented by granitic volcanic-intrusive complexes and mafic dikes, which are genetically related to volcanic-type uranium and porphyry tin deposits, and the mobilization-mineralization of uranium from pre-existing Indosinian granites.

SHRIMP Zircon U-Pb Chronology and Geochemistry of the Henglingguan and Beiyu Granitoids in the Zhongtiao Mountains,Shanxi Province

Henglingguan and Beiyu metamorphic granitoids, distributed in the northwest of the Zhongtiaoshan Precambrian complex, comprise trondhjemites and calc-alkaline monzogranites, displaying intrusive contacts with the Archean Zhaizi TTG gneisses. And the Beiyu metamorphic granitoids consist mainly of trondhjemites, distributed at the core of the Hujiayu anticline fold. New SHRIMP zircon U-Pb dating data show that the weighted mean ^207pb/^206pb ages are 2435.9 Ma and 2477 Ma for the Henglingguan metamorphic calc-alkaline monzogranites and Beiyu metamorphic trondhjemites, respectively, and reveal -2600 Ma inherited core in magmatic zircons. Whole-rock geochemical data indicate that all the Henglingguan and Beiyu metamorphic trondhjemites and calc- alkaline monzogranites belong to the metaluminous medium- and high-potassium calc-alkaline series. These rocks are characterized by relatively high total alkali contents (Na2O+K2O, up to 9.08%), depleted Nb, Ta, P and Ti, and right-declined REE patterns with moderate to high LREEs/HREEs fractionation (the mean ratio of (La/Yb)n = 25). The Henglingguan and Beiyu metamorphic trondhjemites display negative Rb, Th and K anomalies in the multi-dement spider diagrams normalized by primitive mantle. Sm-Nd isotopic data reveal that these granitoids have initial εNd(t) =-1.2 to +2.4 and Nd depleted mantle model ages of TMD = 2622 Ma-2939 Ma. All these geochemical features indicate that these granitoids were formed in an continent-marginal arc, and the trondhjemites mainly originated from partial melting of juvenile basaltic materials and, howbeit, the Henglingguan metamorphic calc-alkaline monzogranites derived from recycling of materials in the ancient crust under a continent-marginal arc. The granitic magma underwent contamination and fractional crystallization during their formation.

Petrogenesis of Indosinian Granitoids in Middle-Segment of South Qinling Tectonic Belt:Constraints from Sr-Nd Isotopic Systematics

South Qinling Tectonic Belt（SQTB）is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures.There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui granitoid plutons at the northeast,Huayang-Wulong-Laocheng granitoid plutons at the central part,Xiba granitoid pluton at the northwest and Guangtoushan-Liuba granitoid plutons at the southwest.These Indonisian granitoids contain a mass of various scale mafic enclaves,which show sometimes clear boundaries and sometimes transitional boundaries with their host granitoids.These granitoids also exhibit metaluminous to peraluminous series,commonly higher Mg# and a wide range of petrochemistry from low-K tholeiite series,through mid-K and high-K calc-alkaline series to shoshonite series and predominated samples are attributed to mid-K and high-K calc-alkaline series.Detailed analyses in Sr-Nd isotopic systematics and petrochemistry reveal that there may be regionally initial granitoid magma of the Indonisian granitoid plutons,comprising Dongjiangkou-Zhashui,Huayang-Wulong-Laocheng,Xiba,and Guangtoushan-Liuba granitoid plutons,which were produced by hybrids of magmas in various degrees,and the initial magmas were derived from both the mantle and the lower continental crust（LCC）sources in the SQTB.The initial granitoid magma further did the magma hybrid with the magmas from the LCC,crystallization fractionation,and assimilation with upper crustal materials during their emplacement to produce these granitoid plutons in the SQTB.These magmatism processes are most likely to occur under continent marginal arc and syn-collision to post-collision tectonic backgrounds.

U-Pb Zircon Geochronology and Geochemistry of Granitoids in the Douling Group in the Eastern Qinling

LA-ICPMS U-Pb zircon dating of the Sanpinggou, Gangou and Fengzishan granitoids in the Douling Group of the Eastern Qinling yields ages of 760-685 Ma, which represents a strong tectono-magmatic event in the southern Qinling during the late Neoproterozoic. Geochemical data show that these intrusions have wide compositions ranging from minor gabbros through diorites to granodiorites. They are relatively enriched in LILE, poor in HFSE and strongly depleted in Nb and Ta, displaying affinities of Ⅰ-type granites formed in an active continental margin with oceanic subduction. In contrast to granitoids, gabbros and enclaves in the granitoids have higher REE abundances, relatively flat REE patterns, lower LILE, slightly higher HFSE and more depletion in Nb and Ta. All these suggest that the gabbros were formed by partial melting of the upper mantle above the subduction zone and the granitoids by the partial melting of the lower crust. Combined with regional geological data, the subduction-related granitoids in the Douling Group, together with the Tuwushan A-type granite with an age of 725 Ma and contemporaneous basic dikes in the Wudang Block, provide evidence for local subduction of oceanic basins between different blocks during the rifting in the Southern Qinling in the Neoproterozoic. Thus, the coexistences of various magmatic rocks formed in different tectonic environments indicate a complicated tectonic evolution and variety of tectonic frameworks in the Qinling area in the Neoproterozoic.

Age and geochemistry of the Neoproterozoic granitoids in the the Songnen–Zhangguangcai Range Massif, NE China: Petrogenesis and tectonic implications

The Songnen–Zhangguangcai Range Massif(SZRM)is located in the eastern Central Asian Orogenic Belt and crops out over an extensive part of NE China.The massif was originally thought to contain numerous Precambrian terranes(e.g.,Xingdong,Dongfengshan,Yimianpo and Zhangguangcailing groups).However,more recent zircon U–Pb dating indicates that the majority of these so-called Precambrian sedimentary and igneous rocks actually formed during either the Paleozoic or Mesozoic and contain only minor Precambrian components(Wang et al.,2014).The presence of Neoproterozoic and Paleoproterozoic detrital zircons with magmatic origins from and Paleozoic units of the SZRM indicating that this area occurs Proterozoic magmatism(Wang et al.,2014),whereas no Proterozoic magmastism has been found.Recently,Pei et al.(2007)reported the ca.1800Ma magmastism,as evidenced by the data of exploration drillholes in the southern Songliao basin.However,an alternative view is that the basement within the SZRM is predominantly Phanerozoic,as evidenced by the presence of Paleozoic fossils and comparatively rare geochronological data(Guo and Liu,1985;Wu et al.,2011),meaning that the ca.1800 Ma rocks in this area may be a tectonically emplaced slice of the North China Craton(Zhang et al.,2005).All of this means that the age and nature of the SZRM basement,and whether this area records Neoproterozoic magmatism,remain unclear.This study presents new geochronological,whole-rock geochemical,and zircon Hf isotopic data for early Proterozoic granitoids within the eastern margin of the SZRM of NE China.These data provide insights into the Neoproterozoic tectonic setting of the SZRM and the links between this magmatism and the evolution of the Rodinia supercontinent.The zircon U–Pb dating indicates that the Neoproterozoic magmatism within the SZRM can be subdivided into two stages:(1)a^917–911 Ma suite of syenogranites and monzogranites,and(2)an^841 Ma suite of granodiorites.The 917–911 Ma granitoids contain high concentrations of Si O2(67.89–71.18 wt.%),K2O(4.24–6.91 wt.%),and Al2O3(14.89–16.14 wt.%),and low concentrations of TFe2O3(1.63–3.70 wt.%)and Mg O(0.53–0.88 wt.%).They are enriched in the light rare earth elements(LREE)and the light ion lithophile elements(LILE),are depleted in the heavy REE(HREE)and the heavy field strength elements(HFSE;e.g.,Nb,Ta,and Ti),and have slightly positive Eu anomalies,indicating they are geochemically similar to high-K adakitic rocks.They have zirconεHf(t)values and TDM2 ages from–4.4 to+1.5and from 1915 Ma to 1592 Ma,respectively,suggesting they were derived from a primary magma generated by the partial melting of ancient thickened lower crustal material.In comparison,the 841 Ma granodiorites contain relatively low concentrations of Al2O3(14.50–14.58 wt.%)and K2O(3.27–3.29 wt.%),relatively high concentrations of TFe2O3(3.78–3.81 wt.%)and the HREE,have negative Eu anomalies,and have zirconεHf(t)values and TDM2ages from–4.7 to+1.0 and from 1875 to 1559 Ma,respectively.These granodiorites formed from a primary magma generated by the partial melting of ancient crustal material.The^917–911 Ma magmatism within the SZRM is inferred to have formed in an orogenic setting,whereas the^841 Ma magmatism formed in an anorogenic setting related to either a post-orogenic tectonic event or the onset of Neoproterozoic continental rifting.It is proposed that the microcontinental massifs within the SZRM formed during or following the final stage of assembly of Rodinia before rifting away from the Tarim Craton in response to Rodinia breakup.

Permian High Ba-Sr Granitoids:Geochemistry,Age and Tectonic Implications of Erlangshan Pluton,Urad Zhongqi,Inner Mongolia

Erlangshan Pluton from Urad Zhongqi, central Inner Mongolia, is located in the middle segment of the northern margin of the North China Plate. The rocks consist mainly of diorites with gneissic structure. Petrochemical characteristics reveal that the diorites belong to metaluminous, high- potassium calc-alkaline series, with chemical signatures of I-type granites. They are characterized by low SiOz contents (56.63%-58.53%) and A/CNK (0.90-0.96), high Al2O3 contents (17.30%-17.96%) and Na20/K20 ratios (1.20-1.70), enrichment in large ion lithophile elements (LILE, e.g., Ba=556-915 ppm, Sr=463-595 ppm), and relative depletion in high field strength elements (HFSE, e.g., Nb, Ta, Ti) in primitive mantle-normalized spidergram, and right-declined rare earth element patterns with slightly negative Eu anomalies (8Eu=0.72-0.90). They have Sr/Y ratios (20-25) evidently less than Kebu Pluton (49-75) to its east. Sensitive high resolution ion micro-probe U-Pb zircon dating of the diorites has yielded an intrusive age of 270±8 Ma. This leads us to conclude that Erlangshan diorites were formed by mixing between the middle or lower crustal-derived magma and minor mantle-derived mafic magma, followed by fractional crystallization, which was trigged by crustal extension and fault activity in post-collisional setting.

Petrogenesis of the Paleoproterozoic Guandishan Granitoids in Shanxi Province:Constraints from Geochemistry and Nd Isotopes

The Guandishan granitoids consist mainly of various granitoid intrusions with different scales, including the Huijiazhuang intrusion, Shizhuang intrusion and Hengjian intrusion, which were formed between 1906 Ma and 1848 Ma. On the basis of geological and petrological characteristics, these granitoids can be classified into two groups： the earlier gneissic granodiorites and monzogranites, and the later massive leuco-monzogranites. Their geochemical and Nd isotopic features indicate that they could be derived from complicated partial melting of supracrustal rocks with an affinity of continental arc materials, such as sandy shale and pelite, and with garnet, pyroxene, hornblende and plagioclase as residual phases. Biotite, feldspar and other minerals were most likely fractionated during the magma evolution. Their source may have an affinity with continental arcs, and the granitoids could be derived from the main syn-collisional to late-orogenic tectonic environment, which may be related to the final amalgamation between the Eastern and Western continental blocks in the North China Craton.

Petrogenesis and tectonic implications of Indosinian granitoids from Western Qinling Orogen,China:Products of magma-mixing and fractionation

The Western Qinling Orogen(WQO) is characterized by voluminous distribution of Indosinian granitoids,the formation of which provides an important window to unravel the geochemical and geodynamic evolution and associated metallogeny.Here we investigate a group of intrusions termed "Five Golden Flowers" based on petrological,geochemical,zircon U-Pb geochronological and Lu-Hf isotopic studies on the granitoids and their mafic microgranular enclaves(MMEs).Our results show that these intrusions are genetically divided into two types,namely,magma-mixing and highly fractionated.The Jiaochangba,Lujing,Zhongchuan,and Luchuba granitoids are biotite monzogranites(220±0.8 Ma to 217±2.6 Ma) with abundant coeval MMEs(220±.1 Ma to 217±2.7 Ma).The rocks contain moderate to high SiO2,high MgO,Rb,Sr,Ba,and Th contents,but low TiO2,P2 O5,and Sc values,A/CNK of <1.1,and a range of εHf(t) values of-11.7 to +2.23 with corresponding TDM2values of 1967-1228 Ma.The MMEs possess K-feldspar megacrysts,abundant acicular apatites,and show lopsided textures.They have lower SiO2,Al2 O3,and Th contents,but higher MgO,TiO2,and Sc,with εHf(t) values of-18.0 to +3.18 and TDM1 of 849-720 Ma.The data indicate that the MMEs were derived from a magma sourced from the enriched lithospheric mantle.We suggest that these host granitoids were produced by partial melting of latePaleoproterozoic to early-Mesoproterozoic lower crust with the involvement of Neoproterozoic SCLM-derived mafic magmas.The Baijiazhuang pluton is dominantly composed of leucogranite(muscovite granite and twomica monzogranite,216±1.5 Ma) without MMEs.The rocks are peraluminous with high A/CNK(1.06-1.27).Compared with the other four granitoids,the Baijiazhuang leucogranite shows higher SiO2 content,markedly lower concentrations of TiO2,MgO,Al2 O3,CaO,and Fe2 O3T,and lower LREE/HREE and(La/Yb)N values.These leucogranites are also rich in Rb,Th,and U,and display marked depletions in Ba,Sr,Ti,and Eu,indicating that they experienced significant fractionation.Zircon εHf(t) values(-10.2 to-3.27) and TDM2(1868-1424 Ma),as well as the Nb/Ta and K2 O/Na2 O values are similar to the other four granitoids,indicating that they are likely to have been derived from a similar source;with sediments playing only a minor role in the magma generation.The low contents of Yb and Y suggest that their partial melting was controlled by garnets and micrographic texture of K-feldspar reflects high-temperature melting through undercooling.Based on the above features,we infer that the Baijiazhuang leucogranite likely represents the product of high degree fractionation of the I-type biotite monzogranite magma which generated the other four granitoids at relatively high temperatures,within magma chambers at mid-crust depths.We propose that the granitoid suite was formed in the transitional setting from synto post-collision during the collisional orogeny between the SCB and NCB,following break-off of the subducted South China Block lithosphere during 220-216 Ma.

Petrochemistry ,Chronology and Tectonic Setting of Strong Peraluminous Anatectic Granitoids in Yunkai Orogenic Belt , Western Guangdong Province ,China

Arguments persist on the genesis and ages for the banded-augen （rapakivi） anatectic granitoids （charnockite） extensively outcropped in the Yunkai （云开） region, western Guangdong （广东） Province. Their petrochemistry, SHRIMP dating, deformational and metamorphic structure were studled. The results show that most granitoids are A/CNK〉1. 1, CaO/Na2O= 0. 62-1. 61 （average 0.94〉0.3）, Al2O3/TiO2 =16.6-60.6 （average 23.68）, depleted high field strong elements Ta, Nb, Zr, strong peraluminous high-K calcalkaline and calcalkaline granitoids in the post-collisional tectonic environment of a subduction-collision orogenic belt in an active-continental margin. The temperatures of charnockite and gneissic garnet-bearing biotite monzonitic granite are obviously higher than those of banded-augen （rapakivi） biotite monzonitic granite, and charnockite and gneissic garnet-bearing biotite monzonitic granite with the evolutional characteristics of A-type granites. The forming ages from banded-augen （rapakivi） biotite monzonitic granite to charnockite and gneissic garnet-bearing biotite monzonitic granite, whose crystallizing zircon SHRIMP ages are （465±10） Ma, （467±10 ） Ma, （435±11 ） Ma and （413±8） Ma, respectively, become younger. This shows that there was an oceaniccontinental subduction-collision and post-collisional extension-delamination-underplating between the Yangtze and Cathaysia plates during the Caledonian, and the granitoids experienced compressional uplift and extensional exhumation during the lndosinian. This provides important evidence of subduction collision of the Yangtze plate to the Cathaysia plate during the Caledonian in South China.