Porphyry deposits emplaced at shallow crustal depths are vulnerable to overprinting during orogenic evolution, yet the balance between exhumation and preservation remains poorly constrained across variable structural settings. We integrate zircon U-Pb geochronology, zircon and apatite fission-track thermochronology, inverse time–temperature modelling, and quartz-hosted fluid-inclusion microthermometry for the Aikengdelesite Cu-Mo, Harizha Ag-Cu, and Halongxiuma Mo-W districts. Zircon U-Pb ages indicate emplacement of ore-related porphyries at 243–242 Ma, 235–223 Ma, and 236–235 Ma, respectively. Single-grain zircon fission-track ages define five post-emplacement cooling clusters at 212–203 Ma, 201–181 Ma, 177–157 Ma, 156–125 Ma, and 120–108 Ma, recording episodic Mesozoic cooling superimposed on long-term thermal relaxation after Triassic magmatism. Apatite fission-track ages, mean track lengths, and inverse t-T models indicate prolonged residence within the apatite partial annealing zone, followed by accelerated late Cenozoic cooling, most clearly expressed at ca. 20–15 Ma. Fluid inclusions yield trapping temperatures of 119–406 °C, salinities of 0.18–21.87 wt.% NaCl eq., and pressures of 19–109 MPa, corresponding to average hydrothermal trapping depths of ca. 5–6 km. In contrast, preferred cumulative post-ore denudation is modest, at ca. 2.1 km for Aikengdelesite, ca. 1.5 km for Harizha, and ca. 2.3 km for Halongxiuma. Integration of thermochronology, fluid inclusion constraints, and alteration assemblages indicates that the three districts are moderately preserved porphyry systems, with deeper stockwork, potassic, and intrusion-proximal domains remaining prospective exploration targets.

Lithium-cesium-tantalum (LCT) pegmatites are a type of peraluminous pegmatites enriched in a variety of rare metal elements, such as Li, Be, Rb, Cs, Nb, Ta, Sn, and W, and they are generally considered to evolve from parental S-type granites through extreme fractionation. The mechanism underlying the enrichment of these rare metals in S-type granites and LCT pegmatites is not yet fully understood. We conducted a comprehensive textural, in situ elemental, and in situ boron (B)-isotopic analysis of primary and secondary muscovite from the Shaliuquan pegmatite in the Quanji Massif, located at the northern edge of the Qaidam Basin, China. The internally zoned pegmatite comprises four main distinct textural and lithological zones from border to core: a mediumgrained muscovite-tourmaline (MT) zone, a muscovite-microcline (MM) zone, a quartzmuscovite (QM) zone, and a Li-muscovite (LM) zone. The increasing concentration of rare metal (Li, Rb, Cs, Nb, and Ta) and fluxing (Li, F, and B) elements-along with decreasing K/Cs ratios-in primary muscovite from the MT zone to the LM zone suggests that fractional crystallization played an important role in producing compositional variations during the magmatic stage. Modeling of elemental ratios (e.g., K/Rb and K/ Cs) suggests that Rayleigh fractionation continued during this stage. However, the Bisotopic composition of primary muscovite decreases at the transition from the QM to LM zones, deviating from the expected Rayleigh fractionation trend. This suggests that the crystallization environment transitioned from a silicic, fluid-undersaturated melt to a fluid-saturated melt. Additionally, textural and chemical differences between primary and secondary muscovite indicate that fluidcrystal interactions were active throughout the magmatic-hydrothermal evolution. Specifically, secondary muscovite in the MM, QM, and LM zones exhibits lower concentrations of Rb, Nb, and Ta compared to its primary counterpart, suggesting its crystallization from a fluid-dominated system through fluid-crystal interactions. This study highlights that Li enrichment in LCT pegmatite systems can be explained by a combination of extreme fractional crystallization and fluid-crystal interactions. However, the depletion of Li in secondary muscovite from the LM zone, relative to primary muscovite, suggests that fluid-crystal interaction contributes not to Li enrichment, but rather to its redistribution.

Whether granitic pegmatite-forming melts originate from granite-related fractionation or direct crustal melting remains debatable. To address the controversy, we collected granitic pegmatite, schist and granitoid samples from the Chakabeishan (CKBS) area in the northeastern Tibetan Plateau, and compiled a comprehensive geochemical dataset of major elements, trace elements, and Li-Hf isotopes. The CKBS granitic pegmatites show lower ThN/UN values and Th, Hf, La, and Yb abundances than the adjacent exposed granitoid plutons. These data, together with overlapping Li isotopic compositions and distinct zircon epsilon Hf(t) values, suggest that the CKBS granitic pegmatites were not derived from extreme differentiation of the adjacent exposed granitoid plutons. The host schist samples show delta 7Li values ranging from -8.43 %o to -1.90 %o. Batch melting simulations reveal that trace element abundances (e.g., Li, Sr, and Sc) and Li isotopic compositions of resultant melts from direct melting of the host schists are decoupled from those of the CKBS granitic pegmatites, precluding the possibility that the granitic pegmatite-forming melts formed via direct melting of the host schists. Considering significant fractionation signatures of the granitic pegmatites and consistent compositions in radiogenic isotopes (e.g., Hf, Nd) between the granitic pegmatites and the host schists, we propose that the CKBS granitic pegmatites formed by a combination of host-schist melting and subsequent fractionation, which is further supported by succinct simulation calculations and regional geological observations. Simulation calculations tracing Li abundances from partial melting sources to pegmatite-forming melts reveal that the Li-rich melting source and the subsequent extreme crystal-melt differentiation are two indispensable conditions for the formation of CKBS Li-rich granitic pegmatites, which provide a new perspective for prospecting more Li-rich granitic pegmatites in the CKBS area and beyond.

This study investigates the zircon and apatite fission track data from the Chakabeishan region, focusing on lithium-beryllium and niobium-tantalum-lithium deposits. The zircon fission track results suggest that the age group of 170-159 Ma represents the peak of lithium mineralization, while the 153-137 Ma group is related to the hydrothermal stage of pegmatites. The 127-106 Ma group marks the end of hydrothermal evolution, and cooling events in the Late Cretaceous (100-94 Ma and 87-72 Ma) are associated with subsequent metallogenic events. Thermal history simulations of apatite fission tracks reveal four exhumation stages: 160-140 Ma (0.86 km), 140-50 Ma (0.57 km), 50-15 Ma (0.43 km), and 15 Ma to present (1.43 km), with a total exhumation thickness of 3.29 km. The study also shows that the rare metal metallogenic thermal events in the Chakabeishan are coupled with those in the northern Qinghai-Tibet Plateau, particularly during the Late Cretaceous to Eocene (100-41 Ma). This coupling reflects widespread thermal effects caused by regional tectonic movements and collisions, providing key insights into the timing and genesis of rare metal mineralization. The findings highlight the importance of zircon and apatite fission track methods in determining the metallogenic age of pegmatite deposits.

Since the Middle Jurassic, the East Kunlun orogenic belt in China has undergone significant denudation. This region offers crucial insights into the tectonic processes that have shaped the Tibetan Plateau. Moreover, the region boasts abundant mineral resources. This study uses techniques, such as zircon and apatite fission track (ZFT&AFT) analyses as well as citing several apatite (U-Th)-He (AHe) ages and FT ages data from the study areas, to unravel the tectonic-thermal evolution and denudation processes. The results reveal ZFT ages spanning from 167 f 5 to 92 f 4 Ma, and AFT ages spanning from 116 f 6 to 64 f 4 Ma. Based on the AFT, ZFT, and AHe data, this paper constructed a tectonic-thermal history model. In the first stage (ca. 170-120 Ma), rapid cooling at 2.00 degrees C/Ma and denudation of 2.85 km occurred. The second stage (ca. 120-20 Ma) showed cooling rates of 0.60 degrees C/Ma and denudation of 1.70 km. In the third stage (ca. 20-0 Ma), rapid cooling with rates of 1.50 degrees C/Ma and denudation of 0.86 km were speculated. The first stage indicates the closure of the Paleo-Tethys Ocean in the Middle Jurassic, with the collision of the Lhasa and Qiangtang blocks with Eurasia along the Bangong-Nujiang suture zone in the Cretaceous. The second stage is mainly related to the northward subduction of the Neo-Tethys Ocean and the far-flung effects of the India-Eurasia collision. The uplift of the Tibetan plateau due to the Himalayan orogeny likely contributed to the third stage. The denuded thickness in the study area since 170 Ma is 5.41 km.

To assess the potential of tourmaline as an indicator for pegmatite evolution and exploration, we measured and compared the geochemical compositions in tourmalines of the barren, Be-rich and Li-rich pegmatites from the Chakabeishan (CKBS) deposit, eastern North Qaidam Tectonic Belt, northeastern Tibetan Plateau. Two types of tourmalines from the barren pegmatites are identified: optically homogeneous fine-grain tourmalines (H-Tur) and optically zoned coarse-grain tourmalines (OZ-Tur). Both H-Tur and OZ-Tur are of magmatic origin, showing high Na/(Na + Ca) (0.961-0.990), YAl (0.389-0.757 apfu) and low Mg/(Fe + Mg) (0.085-0.230). The coretorim delta B-11 increase within H-Tur and OZ-Tur, together with the enrichment of B-11 from H-Tur (crystallized earlier) to OZ-Tur, indicates that fluids were unsaturated in the evolution of barren pegmatites. Compared to H-Tur and OZ-Tur, tourmalines from the Be- and Li-rich pegmatites show higher Nb/Sc (>3:4) and lower Mn/Zn (<1:1), Mn/Li (<3:1), and Sc/Li (<1:500), which are useful indirect criteria of distinction between the fertile and the barren pegmatites. The reliable tourmaline geochemical criteria for further distinguishing the Li-rich from the Be-rich pegmatites are Pb/Sr < 0.11, Nb/Sr < 0.15, and Pb/Co < 4. A compilation suggests that diagrams of (V + Sr)-(Li + Zn), Li-Zn/Sr, Sn/10Nb-Li-100Nb, and Zn/Sn-Li/10Sc-5Sc could discriminate tourmalines of graniterelated pegmatite-type Li deposits from those of other deposits and rocks, showing implications for determining prospective areas for further Li-rich pegmatite exploration by using tourmalines recovered from surface sediments.

Reconstructing the growth model of the Northeastern Qinghai–Tibet Plateau is of significant importance in understanding its tectonic evolution through time. We present 20 new zircon fission track data on samples collected from the Chakabeishan-Shaliuquan district in the North Qaidam Tectonic Belt (NQTB) to constrain its Mesozoic mineralization and exhumation history. Sample ages and characteristics are differentiated by regional thrust fault systems. The mineralized pegmatite ages with high U concentrations can be divided into two groups of 170–168 Ma and 149–137 Ma, recording exhumation and hydrothermal mineralization events, with average cooling and exhumation rates of 0.074 mm/y and 2.305°C/Ma, respectively. Two ZFT ages groups characterized by low U concentrations at the deposit periphery of 125–106 Ma and 99–80 Ma, respectively, are associated with accelerated cooling and exhumation, with mean values of 7.662°C/Ma and 0.245 mm/y. We suggest that the NQTB was positioned in the high background thermal field in the Triassic, and subsequent tectonic extension resulted in the unroofing, cooling and mineralization of the region. The transition from extensional to contractional deformation in the Cretaceous tectonic setting has reactivated regional thrust fault systems and reset the Jurassic ZFT ages, and this exhumation event was influenced by the closure of the Middle-Tethys and Mongol-Okhotsk Oceans, consistent with the double-sided subduction model.

This study presents new fission track data from 40 apatite and 40 zircon samples in the Southern Altai Mountains (SAMs), revealing apatite fission track (AFT) ages of 110 ± 8 Ma to 54 ± 4 Ma and zircon fission track (ZFT) ages of 234 ± 24 Ma to 86 ± 7 Ma. The exhumation rates derived from three thermochronological methods range from 0.01 to 0.1 km/Ma (Age-Elevation method), 0.01 to 0.14 km/Ma (Half-Space thermal model), and 0.027 to 0.075 km/Ma (Age2exhume model). Thermal history modeling using HeFTy software reveals similar thermal histories on both sides of the Kangbutiebao Fault, with a notable cooling event and higher exhumation rates to the northeast. The Late Cretaceous (100–75 Ma) rapid cooling is associated with tectonic reactivation, likely linked to the collapse of the Mongol–Okhotsk Orogen and slab rollback in the southern Tethys Ocean. In the Late Cenozoic (10–0 Ma), cooling and uplift reflect the influence of tectonic stresses from the India–Eurasia collision, which also drove the reactivation of the Kangbutiebao Fault. These findings suggest a complex interplay of tectonic processes driving exhumation in the SAMs from the Late Jurassic to the Early Paleogene.

The Bayan Obo deposit in Inner Mongolia is one of the largest rare earth deposits in the world.There is a large amount of various colored(black,yellow green,dark green,etc.)slates exposed inside and around the deposit.However,the research level of slate is relatively low.In order to determine mineral compositions of the slates,we have analyzed their mineral assemblage characteristics and compositional features by applying the slide full scan,TIMA(TESCAN Intergrated Mineral Analyzer)full scan,electron probe,and LA-ICP-MS.The slide full-scan and TIMA full-scan comparison show that the colored slates are mainly composed of orthoclase with the mximum volume ratio of 86.37％.Within the Bayan Obo deposit,the orthoclase has three types of occurrence forms including cryptocrystalline,single crystal aggregate and single crystal particles.Electron probe microanalyses show that orthoclase particles have SiO2,A12O3 and K2O contents of 59.44％-64.76％,16.89％-19.73％,and 13.96％-17.90％,respectively;with K2O/Na2O ratios of 15.86-45.71.Comparing to other orthoclase particles,the orthoclase particles with zonal texture have relatively low K2O contents,with K2O/Na2O ratios of 15.86-20.85.The LA-ICP-MS analyses show that orthoclase particles contain Ba contents of 700.08× 10-6-47 606.91 ×10-6 and very low contents of other trace elements and rare earth elements which are very limitedly different among various orthoclase particles.With the increase of Ba contents,both overall colors of slates and orthoclases become darker.Therefore,the color darkness of orthoclase is positively correlated with the high Ba content.

The Helanshan Mountain tectonic belt (HTB) is an intraplate deformation belt along the northwestern border of the Ordos Block in the North China Craton. When and why this intracontinental tectonic belt formed, its subsequent uplift and erosion, and the relationships between ranges and adjacent basins remain unclear. To better assess the connections between the temporal and structural activity in HTB, apatite fission-track (AFT) and zircon fission-track (ZFT) analyses were conducted in this study. The lack of adequate FT data from the HTB is a source of contention and dispute. This paper collected samples for AFT and ZFT techniques from the central and southern HTB, trying to improve the research. The ZFT and AFT ages could be divided into the following 7 groups: 279 Ma, 222–213 Ma, 193–169 Ma, 151–147 Ma, 130–109 Ma, 92–77 Ma, and 65–50 Ma. The inverse modeling results of AFT indicate 4 fast cooling episodes of 170–120 Ma, 120–95 Ma, 66–60 Ma, and ~10–8 Ma to the present. Combining the results of FT analysis with radial plot and inverse modeling of AFT, the following eight age groups are believed to reveal the distinct tectonic activities in HTB: the first age group of 279 Ma mainly represented the back-arc extension of the southern HTB; the age group of 222–213 Ma was bounded with NNE-SSE trending contraction between the South China block and North China Craton; the event of 193–169 Ma responded to the post-orogenic collapse followed after the second event; the 151–147 Ma group was interpreted as the eastward extrusion induced by the subduction between Qiangtang and Lhasa blocks; the Early Cretaceous (130–109 Ma) group was not only affected by the rollback of the Pacific Plate, but also denoted the collapse of the thickened lithosphere formed in the Late Jurassic; the Late Cretaceous (92–77 Ma) group was attributed to long-distance impact from the subduction of the Pacific Plate beneath the Eurasian Plate; the event during 65–50 Ma was a correspondence to far-field effect of the onset collision between the Eurasian and Indian Plates; and from 10–8 Ma to the present, the progressive collision of the Indian and Eurasian Plates have a significant impact on the HTB and the northeastern Tibetan Plateau.

The Chakabeishan (CKBS) deposit is a newly discovered pegmatite-type lithium-beryllium deposit in the northern Qaidam tectonic belt of the northern Tibet Plateau. In recent years, some studies have discussed the genesis of the deposit, but the topic remains unclear. This study constrains the genesis of CKBS deposit based on detailed field observations and mineralogical studies, and presents fluid inclusion data and Li isotopic compositions of Li-rich pegmatites and Li-poor pegmatites. The mineralization characteristics of CKBS deposit shows a trend from weak Be mineralization to Li mineralization in the south to north direction, which shows the magmatic differentiation feature. Four types of fluid inclusions are identified: (1) triphase crystal-bearing inclusions (type-1), (2) biphase CO2-rich inclusions (type-2), (3) biphase aqueous inclusions (type-3), and (4) monophase liquid inclusions (type-4). The Li-rich pegmatites mainly contain type-1 inclusions and type-2 inclusions, while Li-poor pegmatites contain type-3 inclusions and some type-4 inclusions. Microthermometric and Laser Raman spectroscopy analyses show that Li-rich pegmatites formed in a low to medium temperature (210.5 - 381.3 degree celsius), low to medium salinity (5.23 - 17.82 % NaCl equiv.) NaCl-H2O-CO2 system, whereas Li-poor pegmatites formed in a low to medium temperature (206.4 - 413.4 degree celsius), low to medium salinity (1.05 10.49 % NaCl equiv.) NaCl-H2O system, which indicates a fluid immiscibility between them. In addition, lithium is greatly enriched in Li-rich pegmatites under the positive effects of CO2. The Li-rich pegmatites display high Li content (8362.4 - 15509.6 ppm) but low 87Li values (1.61 - 1.80 %o). In contrast, the Li-poor pegmatites display low Li content (23.9 - 231.9) but high 87Li values (0.79 - 12.32 %o). This means that the lithium isotopic fractionation is produced by the melt-fluid immiscibility in CKBS deposit, in which a Li-rich system with rich water and poor silicate and a Li-poor system with poor water and rich silicate were formed during the process. Therefore, the CKBS deposit may have formed under the combined effects of magmatic differentiation, melt-fluid immiscibility, and fluid immiscibility.

The Chakabeishan (CKBS) deposit is the first pegmatite-type Li-Be deposit discovered in the eastern North Qaidam Tectonic Belt (NQTB) of Tibetan Plateau. The correct understanding of its petrogenesis and the precise determination of its formation age are of great significance for further regional prospecting and the discovery of new economically valuable rare-metal deposits. Therefore, a systematic study of texture, major-element composition, and U-Pb dating of columbite-tantalite group minerals (CGMs) in the spodumene pegmatite dyke from the CKBS deposit was undertaken. Three types of CGMs were identified, including concentric oscillatory ferrocolumbite (CGMs-1), homogeneous ferrocolumbite (CGMs-2), and irregular ferrotantalite (minor manganocolumbite) with abundant early ferrocolumbite replacement remnants (CGMs-3). The zoning patterns and chemical compositions in the CGMs record the complex evolutionary history of their host pegmatite from the magmatic stage (CGMs-1, disequilibrium crystallization) to the magmatic-hydrothermal transition stage (CGMs-2, equilibrium crystallization) and then to the late metasomatic stage (CGMs-3, replacement/re-equilibrium). CGMs U-Pb dating results suggest that the spodumene pegmatite dyke (No.15) emplaced at 230.1 ± 2.6 Ma. Subsequently, it experienced fluid metasomatism at 221 ± 5.3 Ma. Based on the new age data and published geochronological data, it can be concluded that the spodumene pegmatite dykes in the CKBS deposit formed in an oceanic subduction-related setting, representing a new metallogenic event in western China. Except for the CKBS deposit, a large number of rare-metal pegmatite dykes have also been discovered in the eastern NQTB, indicating that the eastern NQTB may be an important potential rare-metal metallogenic belt that should be explored in detail and arouse painstaking attention.

The Mesozoic-Cenozoic exhumation and deformation of the northeastern Qinghai-Tibetan Plateau generated extensive regional rugged mountains. We aimed to explore the prolonged kinematic evolutionary history since the Mesozoic. We collected Mesozoic magmatic rock samples from the Chaqiabeishan-Shaliuquan lithium-beryllium ore district in the Northern Qaidam tectonic belt (NQTB) to constrain the cooling exhumation history using apatite fission track (AFT) thermochronology. Twenty samples yielded AFT ages from 111 to 11 Ma, including four age groups:111-103, 89-75, 71-47, and 30-11 Ma, with mean track lengths of 12.5-11.2 mu m. Four thermal history phases of 120-90, 90-50, 50-20, and 20-0 Ma were established based on the inverse thermal model and isostatic adjustment of the lithosphere. Additionally, the average cooling rates of the four phases were 1.67 +/- 0.17, 1.25 +/- 0.13, 0.33, and 1.75 +/- 0.5 degrees C/Myr, with a corresponding exhumation amount of 1.15 +/- 0.07 km, 0.98 +/- 0.06 km, 0.86 +/- 0.05 km, and 1.09 +/- 0.06 km respectively, and the maximum exhumation was 6.021-6.787 km since 120 Ma. In the first phase, the far-field effects of Mid-Tethys Ocean subduction and closure drove the rapid exhumation of the research area. The closure of the Neo-Tethys Oceans and the continuing collision of the India-Asia plate disturbed the northeastern plateau, inducing regional backlash fault events in the NQTB, demonstrated in the second phase of thermal history. The third phase of the stable tectonic setting is consistent with previous research results, suggesting a similar cooling history for the NQTB and Qilian Mountains, evidenced by the widespread absence of Eocene to Miocene cooling signals. The rapid exhumation and reactivation of the NQTB and Qilian thrust fault system since 20 Ma represents the final stage of growth and expansion of the northeastern Qinghai-Tibet Plateau.

The petrogenesis of regionally zoned granitic pegmatite veins remains debated. Because of the economic significance, we carried out a study on the Chakabeishan (CKBS) pegmatite-type Li-Be deposit, eastern North Qaidam Tectonic Belt, Northern Tibetan Plateau, by means of in-situ major element and B isotope compositions of tourmalines in the beryl-bearing and spodumene-bearing pegmatite veins. Tourmalines (Tur-Be) from the beryl-bearing pegmatite are homogeneous schorl with low Mg/(Mg + Fe), high Na/ (Na + Ca) and YAl, suggesting that they are of magmatic origin. Two generations of tourmalines (TurLi) from the spodumene-bearing pegmatite are identified: (i) the crystal cores (mostly elbaite and Lirich schorl with subordinate schorl) are consistent with being of magmatic origin crystallized at the magmatic stage; (ii) the crystal rims (schorl) are best understood as the overgrowth at the later hydrothermal stage. Tur-Be and Tur-Li show an obvious difference in core-to-rim B isotopic variation trend with d11B decrease in Tur-Be and increase in Tur-Li. The core-to-rim d11B decrease in Tur-Be results from degassing during its host pegmatitic melt evolution, whereas the core-to-rim d11B increase in Tur-Li is related to fluid exsolution. The estimated d11B values for the initial melts of the beryl-bearing and spodumenebearing pegmatites are -10.46% and -10.78%, respectively, indicating that they most likely originate from protracted fractional crystallization/differentiation of granitic intrusions rather than partial melting of metapelite. Both Mg/(Mg + Fe) ratios and Li abundances in the cores of Tur-Be are lower than those of Tur-Li, suggesting that Tur-Li crystallizes from chemically more evolved melts. (c) 2023 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The Chakabeishan area is located in the northern margin of the Qaidam Basin, Northwest China, and is an important lithium mining area. However, there is a relatively lower research degree and lack of data constraints of tectonic uplift and exhumation. Using fission track technology, new apatite and zircon fission track results have been reported for the first time in order to reveal the tectonic processes and uplift histories of this area. A total of 11 sample results were obtained, these ages could be divided into four groups, namely, 159-144 Ma, 114-100 Ma, 72 Ma and 52-32 Ma, revealing four periods of tectonic activities. Thermal history modelling provided three episodes of uplift at 120-60 Ma, 60-18 Ma and 18-0 Ma. In the first stage, the Southern Qilian Mountains was reactivated and subducted southward due to collision of the Lhasa and the Qiangtang blocks, resulting in rapid uplift in this area. The second stage is tectonic quiescence period corresponding to a relatively steady uplift. The third stage showing rapid uplift caused by the collision between the Indian and Eurasian Plates. The average uplift rate and total uplift amount of the three stages calculated according to the geological thermal histories are 0.039 km/Myr and 3.27 km, respectively. Using the age-closure temperature method, the exhu-mation rate has been calculated as 0.034-0.148 km/Myr from zircon closure-temperature of 250 degrees C to apatite closure-temperature of 100 degrees C and 0.049-0.076 km/Myr form the apatite closure-temperature of 100 degrees C to 15 degrees C of surface temperature. The exhumation rate is fastest from the Late Cretaceous to Eocene and has then changed a little since the Eocene, with the average exhumation rate of about 0.059 km/Myr. Synthesizing the zircon ages and geological characteristics, this area is characterized by multi-stages mineralization, and the metallogenic age is mainly in the Late Jurassic-Cretaceous.

The Chakabeishan Li -Be deposit is a new granitic pegmatite -type rare metal deposit discovered in the eastern North Qaidam Tectonic Belt. To reveal its formation age, decipher its evolution and discuss the correlation of regional metallogenic events, we systematically measured the internal texture, major element composition and U-Pb dating of columbite-tantalite group minerals ( CGMs) from the 19(#) Be -rich granitic pegmatite vein in the Chakabeishan Li -Be deposit. Two types of CGMs were identified, including primary magmatic CGMs-1 and secondary metasomatic CGMs-2. CGMs-1 is the concentric oscillatory or homogenous ferrocolumbitemanganocolumbite. CGMs-2 is the ferrotantalite-manganotantalite with complex zoning patterns such as metasomatic rim and metasomatic worm. CGMs-2 is the metasomatic product of the early -formed CGMs-1 by a Ta-rich melt at the very last evolution stage and generally comprises an Nb-rich dark domain and a Ta-rich bright domain. The U-Pb ages of the magmatic and metasomatic CGMs from the granitic pegmatite vein are consistent within the error ( ca. 229Ma). A compilation shows that the granitic pegmatite swarms in the Chakabeishan deposit crystallized at 240 229Ma. Subsequently, they experienced subsolidus metasomatisms during 217 212Ma. The formation ages, zircon epsilon(Hf) (t) values and t(Dm1), ages of the granitic pegmatites in the Chakabeishan deposit are different from those of the North Qinling Guanpo-Danfeng belt and the Ganze-Songpan-Tianshuihai belt, indicating that the Chakabeishan deposit represents a new granitic pegmatite -type lithium metallogenic event in the northern Tibetan Plateau.

裂变径迹技术以样品用量少、封闭温度低以及测年范围广等优势,被广泛应用于地质学研究中.完全退火或部分退火样品可有效记录岩体的冷却-剥露历史,限制构造活动起始时间,探讨上覆岩石的风化剥蚀历史与矿床保存变化之间的关系,定量化矿床隆升剥蚀量,实现找矿预测;锆石裂变径迹封闭温度对应天然气生成温度区间,可运用于油气勘探研究计算中;近年来结合元素含量分析的裂变径迹技术还可进行物源分析,LA-ICP-MS技术的引进为测量低U含量矿物的径迹带来了曙光.系统总结了磷灰石与锆石裂变径迹退火特性的研究成果,以及温度、化学成分、结晶各向异性及Dpar值等因素对磷灰石径迹退火特性数据解释可能产生的影响,锆石径迹热稳定性的降低主要受制于辐射损伤效应.实验室退火特性研究为了解繁杂的径迹退火化学动力机制提供了重要的理论参考,但在实际的数据解释中需结合地质背景,以获得更为清晰的地质热事件演化研究时间格架.结合径迹测年在矿床、山体隆升剥蚀、盆地热史等研究的典型案例分析,以期为裂变径迹应用的相关研究提供参考.

The Tibetan Plateau, as the roof of the world, records the growth history and formation mechanisms that are critical for evaluating the topographic and climatic evolution of Asia. The rugged highland topography in the northeastern Tibetan Plateau implies an intense tectonic activity, for which targeted research could constrain the exhumation and deformation process. However, the tectonic history since the Mesozoic in the northeastern part of the plateau remains poorly understood. The widespread magmatic rocks and metamorphic basements exposed by the strong thrusting of the North Qaidam Tectonic Belt (NQTB) are a natural laboratory for investigating the growth mechanism of the northeastern Tibetan Plateau. We collected Mesozoic magmatic rock samples at the Chaqiabei Shan–Shaliuquan Li–Be ore district in the NQTB, providing the new Early Cretaceous to Miocene apatite fission-track (AFT) ages and identify three groups: P1 (120–75 Ma), P2 (65–40 Ma), and P3 (25–0 Ma), which coincide remarkably with the deformation and cooling history. AFT data and inverse thermal modeling of the Chaqiabei Shan–Shaliuquan area have reconstructed the multiphase uplift and exhumation history reactivated by the Chaqiabei Shan fault since the Late Mesozoic. The NQTB and Qilian Shan gradually cooled to the AFT closure temperature owing to the far-field effect that was propagated northward by the extinction of the Mid-Tethys Ocean during the Late Jurassic. The synchronous thrusting and formation of the northern plateau frontier resulting from the India–Asia plate collision, revealing a similar cooling model for the NQTB and the Qilian Shan from the Eocene to the Miocene. Since the Miocene, the East Kunlun and Haiyuan sinistral strike-slip fault systems have developed and reactivated the Chaqiabei Shan and Zongwulong thrust faults. The synchronous deformation and reorganization of the NQTB and Qilian Shan represent the final stage of the northeastern Tibetan Plateau’s growth and expansion.

The Bayan Obo deposit is the largest REE resource in the world. Although many isotopic dating methods have been applied, ages based on petrography and closure temperatures still lack discussion. In this study, three digital petrographic images were created based on full-scanning microscopy, BSE, and TESCAN integrated mineral analysis (TIMA), providing a more scientific method for analyzing the mineral types, distributions, and content of the Bayan Obo deposit. By combining the full-scan images, monazites were selected in thin sections and dated in situ. The monazite in the body ores sample yields three 207Pb intercept ages of 657 ± 25 Ma (MSWD = 1.06), 763 ± 16 Ma (MSWD = 1.3), and 689 ± 22 Ma (MSWD = 8.1), and the monazite in one section yields maximum and minimum ages of 1393 ± 142 Ma and 429 ± 24 Ma, respectively. Combined with previous studies, the earliest and major stages of carbonatites, REE, and dikes in the Bayan Obo deposit area were dated at ~1.4 Ga and ~1.3 Ga, respectively. Due to the multiple subduction and accretion events related to the Paleo-Asian Ocean and North China Craton, the Bayan Obo deposit is intensely overprinted, with a tectonic-thermal event recorded at ~1.0–0.2 Ga. The multiple or protracted isotopic ~1.4–0.4 Ga ages in the Bayan Obo deposit account for five reasons. First, the separate thermal events and the partial recrystallization of monazite. Second, the diffusion of daughter products from the host mineral over time. Third, differences in the closure temperatures of different minerals and isotopic chronologies. Four, resetting of the closure system due to high temperature and hydrothermal alteration. Five, the minerals and transformed ores that formed in the Paleozoic. The in situ monazite U–Pb ages in thin sections provide insight into formation sequences from the giant Bayan Obo Fe–REE–Nb deposit.

Narimalaheinan copper deposit is located in the east section of East Kunlun. Its ore forming belt belongs to Qimantage Dulan Variscan polymetallic metallogenic belt. The study of its tectonic activity provides scientific data for subsequent mineral exploration and the preservation and change of the deposit. Apatite fission track chronology method was used to explore the thermal chronological constraints of tectonic activities in different stages in the area, and the uplift rate and amount were quantitatively calculated. The ages of six apatite samples obtained in this study were (64±4), (59±3), (54±4), (57±4), (51±4), (57±4) Ma, P(χ2)＞5%, indicating a single thermal event reaction. The age of apatite samples is positively correlated with the elevation, indicating that the study area is uplifted as a whole by tectonic activities. The fission track length of apatite sample is (106±19)(123±17) μm. The track length is large, and the sample age value has a positive correlation with the track length, indicating that the older samples have a shorter residence time in the return zone and are less affected by later thermal events. The cooling curve simulation results show that the study area has experienced three stages of evolution: rapid uplift, stable uplift and rapid uplift, and the corresponding uplift amounts are 1 429, 285 and 1 571 m respectively. The thermal history in the area was simulated by HeFTy software, the results show that the thermal evolution in the region is divided into three stages. In the first stage (8065 Ma), the uplift rate is 0095 mm/a and the uplift amount is 1 429 m. There is a rapid uplift event, which records the beginning of the closure of the Yarlung Zangbo ocean and the beginning of the collision between India and Asia. In the second stage (6515 Ma) the uplift rate is 0006 mm/a and the uplift volume is 285 m, which occurrs slow uplift and records the collision event between the Indian plate and the Eurasian plate. In the third stage (15 Ma to now), the uplift rate is 0105 mm/a and the uplift volume is 1 571 m, which records the post collision between the Indian plate and the Eurasian plate, resulting in the rapid uplift of the study area at 15 Ma.