Monzonitic Granite Research Articles

Geochronology and Geochemical Characteristics of Granitoids in the Lesser Xing’an–Zhangguangcai Range: Petrogenesis and Implications for the Early Jurassic Tectonic Evolution of the Mudanjiang Ocean

This article focuses on zircon U-Pb isotope dating and a whole-rock elemental analysis of granodiorites, monzonitic granites, granodioritic porphyries, and alkali feldspar granites in the Yangmugang area of the Lesser Xing’an–Zhangguangcai Range. The zircon U-Pb isotope-dating results revealed that these granitic rocks formed during the late Early Jurassic period (182.9–177.2 Ma). Their geochemical characteristics and zircon saturation temperatures suggest that the granodiorites are moderately differentiated I-type granites and the monzonitic granite, granodioritic porphyries, and alkali feldspar granites are highly differentiated I-type granites. The degree of magma differentiation progressively increased from granodiorites to alkali feldspar granites. By combining the regional Nd and Hf isotope compositions, it was inferred that the magma source involved the melting of lower crustal material from the Mesoproterozoic to the Neoproterozoic eras. By integrating these findings with contemporaneous intrusive rock spatial variations, it was indicated that the late Early Jurassic granitoids in the Lesser Xing’an–Zhangguangcai Range formed within an extensional tectonic setting after the collision and closure of the Songnen–Zhangguangcai Range and Jiamusi blocks. Additionally, this study constrains the closure of the Mudanjiang Ocean to the late Early Jurassic period (177.2 Ma).

Geochemistry and Zircon LA–ICP–MS U–Pb Geochronology of the Shuangwang Au Deposit, Shaanxi Province: Implications for Tectonic Evolution and Metallogenic Age

The Shuangwang Au deposit (with a gold resource of approximately 70 t Au), is located in the Fenxian-Taibai fore-arc basin in the West Qinling Orogen of central China. Igneous intrusions in the region include the Xiba granitic pluton and granite porphyry and lamprophyre dykes. The Xiba pluton is composed of granodiorite and monzonite granite. The granodiorite is typical I-type granite, and it yields a crystallization age of 221.1 ± 1.2 Ma and a two-stage Hf model age of 1432–1634 Ma. The monzonite granite shows a transitional characteristic between I-type and A-type granite, and it yields a crystallization age of 214.8 ± 1.2 Ma and a two-stage Hf model age of 1443–1549 Ma. The granitoid was derived mainly from a crust–mantle mixed source. The ages indicate that the granodiorite and monzonite granite formed during two different stages. The REE distribution patterns of the Xiba granitoid exhibit significant fractionation between LREE and HREE, showing right-dipping curves, with an enrichment of LREE and a deficit of HREE. The granodiorite displays a light negative Eu anomaly, while the monzonite granite displays an obvious negative Eu anomaly. The granite porphyry dikes are distributed in the No. I breccia and Jiupinggou granite porphyry, and they yield crystallization ages of 219.9 ± 1.5 Ma and 213.1 ± 0.89 Ma, respectively, and two-stage Hf model ages of 1382–1501 Ma and 1373–1522 Ma, respectively. The lamprophyre dikes in the deposit yield a crystallization age of 214.4 ± 2.7 Ma. After the collision event between the Yangtze and the North China Plates along the Qinling orogenic belt, at approximately 220 Ma in the Late Triassic, the detachment of the slab produced the upwelling of the asthenosphere material. Under conditions of mantle heat and tectonic stress, widespread partial melting of the subducted continental crust and the upper lithosphere mantle occurred, forming granitoids with various degrees of adakite characteristics.

The Relationship between Granitic Magma and Mineralization in the Darongxi Skarn W Deposit, Xiangzhong District, South China: Constrained by Zircon and Apatite

The Xiangho Zng district is the largest low-temperature W-Au-Sb metallogenic area in the world. The Darongxi skarn W deposit in the north of the Xiangzhong district is closely related to biotite monzonite granite, muscovite monzonite granite, and felsophyre, but the nature of granitic magma and its relationship with mineralization is relatively weak. In this paper, U-Pb dating, Lu-Hf isotope, the in situ composition of zircon, and the apatite of biotite monzonite granite, muscovite monzonite granite, and felsophyre in the Darongxi mining area are systematically studied, and the formation age, magma property and source, and their relationship with mineralization are discussed. The values of zircon U-Pb age and the εHf(t) of biotite monzonite granite are 222.2 ± 0.54 Ma and −2.9~−6.4, respectively. The values of zircon U-Pb age and the εHf(t) of muscovite monzonite granite are 220.8 ± 0.58 Ma and −2.7 to −8.1, respectively. The values of zircon U-Pb age and the εHf(t) of felsophyre are 222.3 ± 2.20 Ma and −2.2~−5.4, respectively. Magmatic apatite grains from biotite monzonite granite and muscovite monzonite granite show distinctive core–rim and oscillatory zoning textures in CL images, and demonstrate a bright yellow in colorful CL images. The magmatic apatite has a total rare earth concentration (3766~4627 ppm), exhibiting right-inclined nomorlized rare earth element patterns and obvious negative Eu anomalies. The geochemical data of magmatic zircon and apatite indicate that magma sources are responsible for these intrusions in the Darongxi mining area, mainly derived from the partial melting of the Mesoproterozoic crust, which is rich in W; the magma is rich in F and poor in Cl (F = 2.4~3.3 wt%, Cl = 0.0024~0.0502 wt%). The oxygen fugacity of magmatic zircon (ΔFMQAVG = −4.02~−0.26), the high negative Eu anomaly (δEu = 0.06~0.12) and the low positive Ce anomaly (δCe = 1.09~1.13) of magmatic apatite, and the occurrence of ilmenite all indicate that the redox condition of magma from the Darongxi mining area is reduced. The reduced F-rich crust-source granitic rock and W-rich source provide favorable conditions for the mineralization of the Darongxi reduced skarn W deposit.

Soil geochemistry prevails over root functional traits in controlling soil organic carbon fractions of the alpine meadow on the Qinghai-Tibet Plateau, China

Alpine meadow occupies ～46.7 % of the grassland area and stores more than 60 % of the soil organic carbon (SOC) in the Qinghai-Tibet Plateau, with 3.19 Pg C in the top 30 cm. Parent material can highly influence SOC stocks via various mineral components with divergent adsorption abilities. However, previous studies mainly concentrated on the relation between SOC and parent material in temperate and tropical forest ecosystems, evidences from different environments are needed to gain a holistic understanding. In this study, we explored how the functional distinct SOC fractions (the particulate (POC), mineral-associated (MAOC), and hot-water extractable carbon (HWEOC)) vary among four types of parent materials (monzonitic granite (MG), slate (SL), muscovite schist (SH), and diorite (DI)) by measurements from 16 sites on the Qinghai-Tibet Plateau. We also assessed the plant and geochemical factors in controlling the divergent SOC fractions. We found that MAOC and HWEOC vary strongly, while POC remain stable among parent materials due to sufficient plant input and slow decompositions rate. Moreover, our results revealed that geochemical factors exert dominant controls on each SOC fraction, with soil pH and texture showing a significant influence. Soils developed from the SL displayed the highest MAOC and HWEOC compared with that formed on the other three parent materials due to finer soil texture as well as relative high multivalent Ca and Mg. Furthermore, root traits increased its control on SOC fractions in relatively deeper soil depth (10–30 cm). Taken together, these results provided evidence of the key role of parent material in controlling the divergent SOC fractions in the less weathered alpine regions, emphasizing that parent material and soil geochemistry should be adequately considered in the biogeochemical and Earth system models.

U-Pb Geochronology, Geochemistry and Geological Significance of the Yongfeng Composite Granitic Pluton in Southern Jiangxi Province

The Yongfeng composite granitic pluton, located in the southern section of the Nanling area, is composed of the Yongfeng and Longshi biotite monzonitic granites. In order to reveal the genesis of this composite granitic pluton and its relationship with mineralization, this study conducted zircon U-Pb dating, whole-rock major and trace element analysis, and biotite electron probe analysis. The results show that the Yongfeng composite granitic pluton is rich in silicon and alkali, weakly peraluminous, and poor in calcium and iron. It shows the enrichment of light rare earth elements and a significant fractionation of light and heavy rare earth elements. It also shows the enrichment of large ion lithophile elements and depletion of Ba, K, P, Eu, and Ti relative to the primitive mantle. The contents of TFe2O3, MgO, CaO, TiO2, and P2O5 are low and decrease with increasing SiO2 content. The Yongfeng composite granitic pluton does not contain alkaline dark minerals. Its average zircon saturation temperature is 776 °C, average TFe2O3/MgO is 4.81, and average Zr + Nb + Ce + Y is 280.6 ppm, which correspond to a highly fractionated I-type granite. The Yongfeng and Longshi granites were respectively formed at 152.0 ± 1.0 Ma–151.3 ± 1.1 Ma and 148.9 ± 1.2 Ma. They were formed in the extensional tectonic setting during the post-orogenic stage, under the control of the breakup or retreat of the backplate after the subduction of the Pacific Plate into the Nanling hinterland. The magmatic system of the Yongfeng composite granitic pluton is characterized by high fractionation, high content of F, high temperature, and low oxygen fugacity, which is conducive to mineralization of Sn, Mo, and fluorite.

Alteration Mechanism of Variscan Granite in a Project Area at the Northern Foot of the Tianshan Mountains, China

Long-term erosion of granite—a type of hard rock—by hydrothermal fluids and tectonic movement can lead to a fragmentation of the internal structure of the original rock, transfer/replacement of mineral elements, and alteration of the rock’s basic properties. Such changes can be problematic for the construction of water conservancy, hydropower, and road projects. This study adopted the altered Variscan granite in a water diversion project area at the northern foot of the Tianshan Mountains (China) as the research object, and explored the alteration mechanism using thin section identification, X-ray diffraction, major element analysis, and electron probe and oxygen isotope tests. Results showed that the lithology of the granite in the study area is mainly biotite granodiorite and biotite monzonitic granite. Reductions in both the K+ content in plagioclase and the K+ and Ti4+ contents in chlorite indicate that the alteration types within the study area are mainly clayization of feldspar minerals and chloritization of biotite. Biotite granodiorite and biotite monzonitic granite both have low δ18O values. The δ18O value of biotite granodiorite decreases with increase in the Loss on Ignition. The low-δ18O-value granodiorite due to an alteration by hydrothermal fluids transformed from glacier meltwater, groundwater, atmospheric precipitation, and magmatic water; whereas the monzonitic granite might be formed by the reinvasion of low-δ18O-value granodiorite formed in the early stage, which is remelted, assimilated, and rebalanced. The research findings provide a reference for similar research on altered granite at the northern foot of the Tianshan Mountains, and also lay a foundation for subsequent research on its physical/mechanical properties and engineering characteristics.

Ore Genesis and the Magmatism of the Yuhaixi Mo(Cu) Deposit in Eastern Tianshan, NW China: Constraints from Geology, Geochemistry, Zircon U-Pb and Molybdenite Re-Os Dating

The Yuhaixi Mo(Cu) deposit is a new discovery in the eastern section of the Dananhu-Tousuquan island arc, Eastern Tianshan. However, the genesis of the Yuhaixi Mo(Cu) deposit is still not fully understood. The Yuhaixi intrusion is composed of monzonitic granites, diorites, granites, and gabbro dikes, among which disseminated or veinlet Mo and Cu mineralization is mainly hosted by the monzonitic granites. The LA-ICP-MS zircon U-Pb dating yields emplacement ages of 359.4 ± 1.6 Ma for the monzonitic granite, 298.8 ± 1.8 Ma for the diorite, and 307.0 ± 2.3 Ma for the granite. The Re-Os dating of molybdenite hosted by monzonitic granite yields a well-constrained 187Re-187Os isochron age of 354.1 ± 6.8 Ma (MSWD = 1.7) with a weighted average age of 344.5 ± 3.1 Ma. The Mo mineralization is closely associated with the Yuhaixi monzonitic granite. The Yuhaixi monzonitic granite rocks are characterized by high silica (SiO2 > 70 wt.%), low MgO (0.23–0.36), Ni, Cr contents, and they are enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: e.g., K, Ba, Pb and Sr), and depleted in heavy rare earth elements (HREEs) and high field-strength elements (HFSEs: e.g., Nb, Ta and Ti). They are weak peraluminous and have high εHf(t) (11.37–17.59) and εNd(t) (1.36–7.75) values, and varied initial 87Sr/86Sr (0.7037–0.7128) values. The Yuhaixi post-ore granites exhibit similar geochemical and isotopic signatures to the Yuhaixi monzonitic granite. These characteristics suggest that the Yuhaixi felsic rocks are likely sourced from the partial melting of the juvenile lower crust. The Yuhaixi diorite has low SiO2, and K2O contents, relatively high Na2O, MgO (Mg# = 45–53) contents, and depletions in HFSE (e.g., Nb, Ta, and Ti). These geochemical features, coupled with isotopic data such as low initial 87Sr/86Sr (≤0.7043), high εNd(t) (2.5 to 3.0) and εHf(t) (≥11.6) values, and young Hf model ages, suggest that their parental magmas possibly originated from the partial melting of the depleted lithospheric mantle that was metasomatized by hydrous melts or fluids from the subducting oceanic plate. Integrating our new results with previous works on the Dananhu-Tousuquan island arc belt, we suggest that the Yuhaixi Mo(Cu)deposit is likely sourced from the juvenile lower crust, which was formed in an arc setting, where the bipolar subduction of the North Tianshan oceanic slab forms the Dananhu Tousuquan belt to the north and the Aqishan-Yamansu belt to the south. The eastern section of the Dananhu-Tousuquan island arc is a promising target for late Paleozoic porphyry Mo(Cu) deposits.

Contrasting appinites, vaugnerites and related granitoids from the NW Iberian Massif: insight into mantle and crustal sources

Abstract. Post-collisional Mg–K-rich mafic rocks with associated granitoids appear regularly in most orogens. They are relevant to evaluate the mantle role in the genesis of granitoids and thereby of the continental crust itself. The most characteristic Mg–K mafic rocks in the Variscan Iberian Massif are appinites and vaugnerites. Two examples with associated granitoids from NW Iberia have been compared to assess their mantle and crustal sources and the magmatic processes involved in their formation. Related granitoids are tonalites, granodiorites and monzonitic granites. Available whole-rock major and trace element compositions, as well as Sr and Nd isotopes, were used for this comparison, along with new Sr–Nd isotopic data. The appinite–granitoid association is calc–alkalic, whereas the vaugneritic one is calc–alkalic transitional to alkali–calcic. Vaugnerites are more enriched in Mg and K, compatible and incompatible trace elements and display more fractionated rare-earth element (REE) patterns than appinites. Associated granitoids provide similar differences. Appinites and vaugnerites have Sr and Nd crustal isotopic signatures resulting from partial melting of a different subduction-type metasomatised mantle: amphibole spinel lherzolites for appinites and more refractory and deeper amphibole phlogopite ± garnet peridotites for vaugnerites. Further interaction of these basic melts with coeval granitoids occurred during their ascent and emplacement. The monzonitic granites derived from partial melting of metaigneous acid granulites, without discarding contribution of metasediments and/or an increasing role of biotite incongruent melting in those related to vaugnerites. An assimilation with fractional crystallisation process between appinite magmas and granulites could explain tonalites and granodiorites. This process was not confirmed for granodiorites related to vaugnerites.

U-Pb and Re-Os geochronology and geochemistry of the Ulgen hidden porphyry Mo deposit in the Derbugan metallogenic belt (NE China): Insights into petrogenesis and tectonic setting

The Ulgen porphyry Mo deposit, recently discovered in the northeastern segment of the Derbugan metallogenic belt, NE China, is a large and hidden ore deposit. Investigation of this deposit provides insights into the geodynamic background and metallogenic mechanism of Mesozoic porphyry Mo deposits that are exposed elsewhere in NE China. The host rocks consist of muscovite monzonitic granite (MMG) and biotite granitic porphyry (BGP), which are intruded into Lower and/or Middle Jurassic intermediate-felsic volcanic-sedimentary rocks and pre-ore monzogranitic porphyry (MP). Zircon laser ablation−inductively coupled plasma−mass spectrometric (LA-ICP-MS) U-Pb age dating indicates that the MMG and BGP were emplaced at 144.9 Ma and 144.7 Ma, ca. 14 m.y. younger than the intrusion age of MP (159.3 Ma). Molybdenite Re-Os isotopic dating indicates that Mo mineralization occurred at 144.9 Ma, almost simultaneously with the 145 Ma magmatic activity. Geochemically, all of the Ulgen granitoids are enriched in large ion lithophile elements (e.g., Rb, Th, U, and K) and light rare earth elements, and are depleted in high field strength elements (e.g., Nb, Ta, and Ti). The pre-ore MPs belong to I-type granites with moderately negative Eu anomalies (Eu/Eu* = 0.62−0.65), whereas the syn-ore MMGs exhibit S-type affinity with pronounced negative Eu anomalies (Eu/Eu* = 0.29−0.39). The ore-forming BGPs display adakite-like geochemical features in terms of high-Sr, low-Y, and low-Yb contents, and slightly negative Eu anomalies (Eu/Eu* = 0.72−0.74). All intrusive rocks have relatively low initial (87Sr/86Sr)i ratios (0.7044−0.7055) and positive εNd(t) values (+1.15 to +2.65), positive εHf(t) values (+4.0 to +9.4), young two-stage Nd and Hf model ages (tDM2(Nd) = 841−731 Ma, tDM2(Hf) = 943−604 Ma), and moderate (206Pb/204Pb)i (18.300−18.402), (207Pb/204Pb)i (15.557−15.564), and (208Pb/204Pb)i (38.180−38.307) ratios. Therefore, it is most likely that these intrusive rocks originated from a mixture of two sources of magma derived from the mantle and juvenile lower crust, in which there were variable degrees of the fractional crystallization of ilmenite, apatite, and plagioclase. Rather than the partial melting of oceanic slabs, the fractional crystallization of hornblende and accessory minerals (e.g., ilmenite and apatite) induces the adakitic geochemical signature of BGPs. Compared with the BGPs, the MPs had a relatively deeper magma source region, whereas the MMGs had a relatively shallower magma source region. The BGPs and the Mo-bearing fluids of the Ulgen deposit were most probably derived simultaneously from magma that was generated at an extensional setting following the closure of the Mongol-Okhotsk Ocean during the latest Jurassic. Enrichment of Mo by late-stage fractional crystallization most likely played an important role in concentrating Mo during the formation of the Ulgen hidden Mo deposit.

Geochemistry, geochronology and Sr–Nd–Hf isotopes of Paleozoic granitoids in the Chinese Altai, NW China: constraints on the conversion from subduction–accretion to syn-/post-collision

The Altai region of China features abundant granitoids, which can be used to reconstruct the tectonic evolution of the orogen. We conducted petrological, geochronological, geochemical and isotopic analyses on several representative granitoids from the Altai region. U‒Pb dating revealed ages of 444 ± 3 Ma for gneissic granites, 406 ± 8 Ma for syenogranites, 280 ± 6 Ma for diorites, 278 ± 3 Ma for two-mica monzonitic granites and 269 ± 3 Ma for muscovite granites. The Ordovician gneissic granites have I-type arc-related element characteristics and are derived from volcanic magmas extracted from the mantle wedge and then metasomatized by subducted sediment in a continental arc. The Devonian syenogranites show dual I-type arc and within-plate granite geochemical signatures, suggesting derivation from volcanic magmas extracted from the lithospheric mantle metasomatized by subducted fluid/melt in a back-arc basin. The Permian diorites are Mg-diorites derived from a mixed-magma source involving residual subducted basaltic oceanic crust and lithospheric mantle. The two-mica monzonitic granites are S-type granites originating from the crustal recycling of sedimentary rocks, whereas the muscovite granites are leucogranites resulting from the anatexis of ancient metasedimentary rocks. Their tectonic setting is syn-/post-collisional. By combining these results with previously published data, we propose that the Chinese Altai region experienced mid- to late Ordovician continental arc magmatism, early to mid-Devonian back-arc extension and early to mid-Permian arc–arc syn-/post-collision. Supplementary material: Supplementary Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.6420236

Geochronology and skarn mineralogy of the Akesayi Fe deposit in the Western Kunlun, Xinjiang: Implications for mineralization process

The Akesayi deposit, located in the eastern part of the Tianshuihai terrane of the Western Kunlun Orogenic Belt, Xinjiang, China, is a recently discovered medium-sized magnetite deposit containing approximately 51 million tons of ore with an average grade of 41 wt%. This deposit is hosted by skarns at the contact between monzonitic granite, diorite porphyry, and medium to low-grade metamorphic clastic rocks of the Permian Huangyangling Group. The ore types include banded, disseminated, and massive ores. The metallogenic process can be divided into prograde skarn, retrograde skarn, oxide, quartz-sulfide, and carbonate stages. The metallic minerals include magnetite and pyrite, and the gangue minerals include olivine, garnet, hedenbergite, hornblende, actinolite, biotite, cummingtonite, chlorite, quartz, and calcite. The zircon U–Pb dating of biotite adamellite intrusion and schist together constrains the formation age of the host rocks in the Akesayi Fe deposit to 217–272 Ma. Rb–Sr dating of eight garnet samples yields an isochron age of 12.41 ± 0.31 Ma, which is almost identical to the 12.56 ± 0.50 Ma age obtained via Sm–Nd dating of eight garnet samples. Furthermore, zircon U–Pb dating yields ages of 12.76 ± 0.12 Ma and 12.37 ± 0.18 Ma for diorite porphyry and monzonitic granite near the Fe orebodies, respectively. The initial Sr isotopes of garnet ((87Sr/87Sr)i = 0.710901) prove that the diorite porphyrite ((87Sr/87Sr)i = 0.709283) is related to skarn mineralization. Thus, the Akesayi deposit is a skarn-type iron ore related to the middle Miocene diorite porphyry. The mineral assemblage indicates the extensive development of manganese-skarn in the Akesayi mining area. The manganese content of host rocks of the deposit is low, and the source of manganese in the skarn may mainly come from the hydrothermal fluids associated with Miocene diorite porphyry emplacement. The compositional variations between the cores and rims of single garnet grains and different stages of tephroite indicate the concentration characteristics of the hydrothermal system, particularly manganese content, which evidently changed during hydrothermal activity. The endmembers of garnet and pyroxene suggest that the ore-forming environment transformed from a relatively reduced acidic environment to an alkali-rich, high-oxygen fugacity environment. The widely developed chlorine-rich amphiboles and biotite indicate that the hydrothermal fluids were rich in chlorine and may have been related to the diorite porphyrite intrusion near the ore bodies. The iron mineralization of the Akesayi deposit is analogous to the Gangdese Miocene porphyry–skarn polymetallic mineralization, which occurred during the Miocene in a post-collisional tectonic setting. Considering the series of Miocene intrusives discovered in West Kunlun, we propose that Miocene skarn Fe mineralization events occurred in West Kunlun, and that this area has great prospecting potential.

Early Triassic Monzonite–Granite Series in Eastern Kazakhstan as a Reflection of Siberian Large Igneous Province Activity

We provide the results of studying the internal structure and composition of the rocks of the Semeitau and Delbegetei massifs located in Eastern Kazakhstan. It was previously believed that these massifs have different ages and were formed in different geodynamic settings. The U-Pb zircon age from the monzonites and quartz monzonites was determined to be 249 ± 2 Ma, which showed the same Early Triassic age of the massifs. Both massifs are composed of rocks of the same monzonite–granite series of rocks with a significant proportion of high-silica rocks (leucocratic granites). Intermediate rocks are formed due to the differentiation of subalkaline mafic magmas, and the felsic rocks (rhyolites and granites) are the result of partial melting of crustal substrates. The massif formation model assumes the intrusion of mafic magmas into the crust, their differentiation and mixing with crustal melts, and then the intrusion of various rocks into the upper crustal levels. Analysis of the geological position, age and composition of the rocks allows us to conclude that the Semeitau and Delbegetei massifs were formed in an intraplate geodynamic setting. The activity of the mantle plume is the most probable reason for their formation. The Semeitau and Delbegetei massifs can be included in the southern part of the range of the Early Triassic Siberian Large Igneous Province.

Zircon U-Pb Ages and Geochemistry of the Granite in the Xintianling Tungsten Deposit, SE China: Implications for Geodynamic Settings of the Regional Tungsten Mineralization

The Xintianling tungsten deposit is a super-large deposit in the Nanling tungsten–tin mineralization belt, which is genetically associated with the early-stage hornblende-biotite monzonitic granite of Qitianling pluton. The orebodies predominantly occur as veins and lenses within skarn rocks between Xintianling granite and limestone (Shidengzi group). In this work, whole-rock major and trace elements and zircon U–Pb ages of the Xintianling granite were studied in an attempt to investigate the geochronological framework, petrogenesis, tectonism, and metallogenesis with regard to the deposit. The petrographic and geochemical analyses indicated that the Xintianling granite consists of three intrusive units of medium- and coarse-grained biotite granite, fine-grained biotite granite, and granite porphyry, of which the biotite granite was strongly associated with mineralization. Biotite granite rocks are highly K-calc-alkaline and weakly peraluminous, with A/CNK ratios ranging from 0.99 to 1.05. Late-granite porphyry is aluminum-supersaturated with a high evolution degree, whose geochemical characteristics suggest that it is either an I- or S-type granite. LA-ICP-MS zircon U-Pb dating revealed that medium- and coarse-grained biotite granite (162.3 ± 1.2 Ma, MSWD = 1.3), fine-grained biotite granite (161.8 ± 1.3 Ma, MSWD = 1.8), and granite porphyry (154.3 ± 1.6 Ma, MSWD = 2.4) formed in the late Jurassic. The emplacement of the Qitianling A-type granite and associated tungsten-tin polymetallic mineralization is a continuous evolution process, and they are products of the large-scale mineralization of the Nanling in the middle–late Jurassic (150–160 Ma). Under the tectonic setting of the Mesozoic lithospheric extension, asthenosphere upwelling along deep-fault, intensive mantle–crust interaction processes probably provide not only the high heat flow, but also partly mantle-derived material for large-scale W-Sn-polymetallic mineralization in this area.

Geothermal Mechanism and Reservoir Characterization with Multiscale Analysis of the Potential Field and MT Profile in the Yanqing-Huailai Basin, North China

Abstract Geothermal energy has attracted increasing attention worldwide due to its abundant reserves, stability, and sustainability. Based on the survey of geothermal resources in the Yanqing-Huailai Basin, this paper conducts comprehensive data study, demonstrates geothermal distribution and multiscale characteristics, and constructs the geothermal mechanism and conceptual model to promote regional geothermal energy development and utilization. Our study proposes to characterize geothermal reservoirs using geophysical data ranging from the representative geothermal field scale to the basin scale. Hydrochemical samples were also collected. According to the results of multiscale analysis and interpretation, combined with field geological and geothermal investigations, it is concluded that the Dahaituo pluton is composed of acid granite and monzonite granite, with low gravity and high magnetic anomaly. Its intrusion and development are responsible for the local geothermal anomaly. Multiscale analysis and source depth estimation of potential field data and MT profile interpretation were carried out. The regional thermal structure and reservoir characteristics were demonstrated from the deep to the shallow. In addition, according to the regional geological background and geophysical interpretation, a three-dimensional geological model is constructed to characterize the distribution law and genetic mechanism of geothermal anomalies. The study shows that strong Cenozoic tectonic movement and the intrusion and development of rock mass are the main factors causing local geothermal anomaly. The development of regional deep and major faults and extensional structures, as well as the channels and space formed by the breaking of rocks at the intersection of faults, provides advantageous conditions for the upwelling, migration, and convergence of geothermal fluids. The recharge of surface water in the intermountain basin and thermal convection drive the circulation of the geothermal system.

Petrogenesis of the early Jurassic Ora batholith in south‐western Cambodia

The Ora batholith in south-western Cambodia is situated in the western part of Indochina and east of the Inthanon–Bentong–Raub Palaeo-Tethys suture and thus bears significant constraints for the equivocal crustal generation of the Palaeo-Tethys orogenic belt in Mainland South-east Asia. The Ora batholith consists of monzonitic granite (Group 1), alkali-feldspar granite (Group 2), and biotite granite (Group 3), and they yield similar Early Jurassic ages of 186.0–199.7 Ma. Group 2 are high-silica (SiO2 > 75 wt%) rocks with lower TiO2, Al2O3, FeOtot, MgO, CaO, P2O5, Eu, Ba, Sr, P, and Ti contents compared to those of the other two groups. Group 2 and 3 are classified as fractionated-type granitoids, whereas Group 1 is unfractionated granite as the complementary residual of the fractionated rocks. All groups have positive εHf(t) values from +2.29 to +8.83, suggesting they were cogenetic and derived from partial melting of the lower crust with the addition of asthenospheric mantle material. Integrating with other granitoids in this region, we suggest the Ora granitoids belong to I-type granitoids. Our petrogenetic and zircon U–Pb age data suggest the Ora granitoids were related to the Early Jurassic post-collisional magmatism that resulted from crustal thickening and mantle lithospheric delamination due to a denser crustal root than the underlying mantle lithosphere after the Palaeo-Tethys Ocean closure and collision between the Sibumasu and Indochina terranes. Then the following upwelling of the asthenospheric mantle not only heated and caused partial melting of the lower crust and mantle wedge, but also supplied asthenospheric material to generate the high-εHf(t) magma.

Geochronology and geochemistry of monzonitic granites from the eastern central Qilian Block, northwest China

Geochronology and geochemistry of monzonitic granites from the eastern central Qilian Block, northwest China

Triassic tungsten mineralization in Nanling metallogenic belt: A case study of the Zanshi tungsten deposit in the Yajiangqiao area, eastern Hunan Province, China

The Nanling metallogenic belt is rich in critical metal minerals, e.g., tungsten, tin, and rare earth element (REE). The newly discovered Zanshi tungsten deposit, located at the northeastern part of the Nanling metallogenic belt, has drawn great attention from geologists for its rare Triassic magmatic-hydrothermal event in this region. Based on detailed field work, a series of geochemical and geochronological analyses, including whole-rock geochemical analyses consisting of major and trace elements, LA-ICP-MS monazite U-Pb dating of the granites and quartz Rb-Sr and muscovite 40Ar-39Ar isotopic dating of the ore-bearing quartz veins, were carried out in this study, aiming to constrain the rock- and ore-forming ages of the deposit as well as the petrogenesis of granites. The whole-rock geochemical analyses, the medium to fine-grained two-mica monzonitic granites in the Zanshi tungsten deposit are peraluminous S-type granites and derived from the partial melting of metamorphic graywackes in a post-collisional extensional tectonic setting. The LA-ICP-MS monazite U-Pb dating on the two medium- to fine-grained two-mica monzonitic granite samples yields weighted average ages of 218.2 ± 1.2 Ma (MSWD = 1.3) and 221.7 ± 1.7 Ma (MSWD = 2.7), respectively. These ages are consistent with the quartz Rb-Sr and muscovite 40Ar-39Ar isotopic ages of the ore-bearing quartz veins, which are 218.7 ± 3.2 Ma and 215.1 ± 2.0 Ma, respectively, revealing that the tungsten mineralization in this deposit is related to the Triassic magmatic-hydrothermal activity. Combined with previous studies, the Zanshi tungsten deposit likely experienced about 5 M.y. of magmatic evolution and 3.6 M.y. of mineralization. Meanwhile, the cooling rate of the ore-forming fluids of this deposit was about 111 °C/M.y., which may be regarded as a controlling factor which affects the ore grade of the deposit.

Geochronology and Geochemistry of Felsite Dike from Shanmen Silver Deposit in Central Jilin Province, China, and Its Geological Significance

Shanmen silver deposit is located on the south section of Daheishan horst polymetallic mineralization belts in central Jilin province, Northeast China. The deposit supplies not only the greatest portion of silver in Jilin province, and a significant amount of gold also. The deposit exhibits a closely spatiotemporal relationship with Mesozoic ore-hosting diorite and granite intrusions and Mesozoic basic-felsic dikes. Among the dikes the felsite one occurred at the same fault zone as the silver-bearing veins in the deposit, implying that felsite dike has an important theoretical and ore-prospecting significance. Here, we mainly investigate felsite dike based on zircon LA-ICP-MS U-Pb geochronology, petrochemical compositions. Zircon U-Pb dating from felsite dike yielded a weighted mean age of 163.1± 2.3 Ma, which is slightly younger than the ore-hosted intrusions of quartz diorite (167.6± 1.9 Ma) and monzonite granite (167.0 ± 1.5 Ma), indicating that petrogenetic age of felsite dike is late Jurassic. Major element data suggest that felsite dike is of granodioritic and granitic in chemical composition, belonging to high-K calc-alkaline and shoshonite series, with SiO₂, K₂O+Na₂O, Al₂O₃, TiO₂, CaO and MgO contents ranging from 62.98-79.18%, 4.13-5.3%, 13.31-16.01%, 0.05-0.57%, 0.15-3.07%, and 0.28-1.8%, respectively. Felsite dike is enriched in Rb, U, and Pb, and depleted in Ba, Nb, Sr, Ti and other high field strength elements. REE contents of felsite dike are in the range of 28.42-214.23 ppm, showing weak negative Eu anomalies with Eu/Eu* ratios of 0.24-0.61. Except for the altered felsite sample with SiO₂ content of 79.18%, the distribution characteristics of trace elements and rare earth elements in felsite dike are similar with those of ore-hosted intrusion of granite and diorite. The geochemical features show that late Jurassic felsite dike was formed in the tectonic background of active continental margins associated with subduction in the Paleo-Pacific Plate. The underplating of mantle-derived magma caused the partial melting of the meta-sediment in lower crust materials to form the mid-late Jurassic magmatism and late Jurassic silver mineralization.

Magma evolution and mineralization of Longmenshan lithium-beryllium pegmatite in Dahongliutan area, West Kunlun

西昆仑大红柳滩地区相继发现了众多伟晶岩型锂铍矿床，已成为我国新的锂资源基地。目前关于这些锂铍花岗伟晶岩的成因多强调其源于地壳深熔形成的二云母二长花岗岩的结晶分异，但研究区出露的同时代的黑云母花岗岩与成矿的关系没有被讨论和关注。为了探讨黑云母花岗岩与成矿的关系，作者对龙门山矿区黑云母花岗岩、二云母二长花岗岩、花岗伟晶岩以及与成矿相关的细晶花岗岩开展了详细的地球化学及年代学研究。结果显示：1）黑云母花岗岩与二云母二长花岗岩具相似的地球化学特征，富集Rb、La和Nd，亏损Ba、Nb、Sr、P和Ti元素，均表现出S型花岗岩的特征；2）从黑云母花岗岩→二云母二长花岗岩→细晶花岗岩，表现出连续分异演化的特征；3）黑云母花岗岩的锆石LA-ICP-MS U-Pb年龄为216.8±0.85Ma，二云母二长花岗岩的锆石SIMS U-Pb年龄为216.0±1.5Ma，细晶花岗岩的锆石LA-ICP-MS U-Pb年龄为209.5±1.2Ma，花岗伟晶岩的锡石LA-MC-ICP-MS U-Pb年龄为211.3±5.0Ma，这意味着从黑云母花岗岩到二云母二长花岗岩与细晶花岗岩的形成时间是连续的并且是接近的。基于此，作者认为大红柳滩地区的二云母二长花岗岩与锂铍伟晶岩源于黑云母花岗岩的结晶分异。实验岩石学显示，变杂砂岩或黑云母片麻岩的黑云母脱水熔融可形成黑云母花岗岩，据此推测大红柳滩地区的大规模黑云母花岗岩源于地壳深部麻粒岩相变质过程黑云母和少量角闪石的脱水熔融。;Several lithium-beryllium deposits of pegmatite type have been found in Dahongliutan area, West Kunlun, which is a new lithium resource base in China. The origin of these deposits was emphasized as crystallization differentiation of the two-mica monzonitic granite formed by anatexis of the crust, but the relationship between the biotite granite in the study area and mineralization has never been discussed and concerned. In order to explore this problem, we conducted geochemistry and chronology studies of biotite granite, two-mica monzonitic granite, granitic pegmatite, and aplitic granite related to mineralization in Longmenshan. The results show:1) The biotite granite and two-mica monzonitic granite have similar geochemical features of S-type granite and are enriched in Rb, La and Nd, depleted in Ba, Nb, Sr, P and Ti; 2) From biotite granite, two-mica monzonitic granite to aplitic granite, the process exhibits a continuous differential evolution of the magma; 3) The zircon LA-ICP-MS U-Pb age of biotite granite is 216.8±0.85Ma, the zircon SIMS U-Pb age of two-mica monzonitic granite is 216.0±1.5Ma, the zircon LA-ICP-MS U-Pb age of aplitic granite is 209.5±1.2Ma, and the cassiterite LA-MC-ICP-MS U-Pb age of granitic pegmatite is 211.3±5.0Ma. This means that the formation time of granite from biotite granite, two-mica monzonitic granite to aplitic granite is continuous and contiguous. Based on this, we believe that the two-mica monzonitic granite and the lithium-beryllium pegmatite in Dahongliutan area are formed by the crystallization differentiation of biotite granite. Experimental petrology showed that biotite dehydration-melting of meta-greywacke or biotite gneiss forms biotite granite, and it is speculated that the extensive biotite granite in Dahongliutan area originated from the dehydration-melting of biotite and some amphibole during granulite facies metamorphism in the lower crust.

The Early Paleozoic intrusive magmatism and tectonic thermal evolution in the Hala Lake area, southern Qilian, NW China

南祁连增生杂岩带作为祁连造山带的构造单元之一，是研究祁连造山带与柴达木地块构造演化及二者耦合关系的关键地区，得到了国内外学者的广泛关注。前人对南祁连增生杂岩早古生代以来的构造热演化历史研究相对较少，且缺少相对准确的年代学数据约束。本文通过对南祁连增生杂岩带哈拉湖地区阿腊郭勒岩体二长花岗岩开展LA-ICP-MS锆石U-Pb定年、岩石地球化学特征、锆石和磷灰石裂变径迹年龄测试及热历史模拟，并结合野外地质调查和构造演化特征，揭示南祁连增生杂岩带哈拉湖地区的构造热演化历史和山脉隆升过程。结果显示：（1）南祁连哈拉湖地区在中志留世发生一期岩浆侵入事件（425~429Ma），其形成的岩体具有壳源花岗岩特征，产出于同碰撞的构造环境，说明该期岩浆事件是与祁连洋洋壳俯冲结束后的柴北缘地区大陆碰撞过程中的岩浆活动有关；（2）该岩体经历了中志留世至晚泥盆世的岩浆侵位与快速冷却阶段以及晚泥盆世-侏罗纪的构造平稳与缓慢冷却阶段；（3）早白垩世以来的中低温冷却和快速隆升的构造热演化历史。此外，祁连山地区自始新世以来经历了多期与印度欧亚-板块碰撞有关的构造变形。;As an important tectonic unit of the Qilian orogenic belt, the southern Qilian accretionary belt plays a significant role in studying the tectonic evolution and their coupling relationship between the Qilian orogenic belt and the Qaidam block. Although wide attention has been paid to this belt by geologists all over the world, the tectono-thermal evolution of the southern Qilian accretionary belt since Early Paleozoic is still unclear due to the lack of relatively precise geochronological data constraints. In this paper, we integrated field obervations, LA-ICP-MS zircon U-Pb age, geochemical characteristics, low-temperature themochronometry (apatite- and zircon-fission track ages) and thermal history modeling to provide constraints on the tectono-thermal history and range growth of the Hala Lake area in the southern Qilian accretionary belt. The results suggest that the southern Qilian accretionary belt experienced a multi-phase tectono-thermal evolution history, including:(1) Early Paleozoic intrusive magmatism and rapid cooling due to the Qilian orogeny from Middle Silurian (425~429Ma) to Late Devonian, with continental crust resource characters and generating from syn-collisional tectonic setting of the monzonitic granites, which indicates that this period of magmatism was related to the continental's collision of southern Qilian accretionary belt and the Qaidam block after the ocean crust subduction of Qilian Ocean; (2) tectonic quiescence and slow cooling during Late Devonian to Jurassic; (3) mid-low temperature cooling and rapid uplift since Early Cretaceous. Furthermore, the Cenozoic Qilian Shan thrust belt also experienced multi-phase structural deformations since Eocene as a result of the India-Asia collision.