Granitic pegmatite deposits, which are usually products of orogenic processes during plate convergence, can be used to demonstrate regional tectonic evolution processes. In the eastern Tibetan Plateau in China, the Jiajika, Dahongliutan, Xuebaoding, Zhawulong, and Ke’eryin rare metal pegmatite deposits are located in the southern, western, northern, midwestern, and central areas of the Songpan–Ganzê orogenic belt, respectively. In this study, we dated two muscovite Ar–Ar ages of 189.4 ± 1.1 Ma and 187.0 ± 1.1 Ma from spodumene pegmatites of the Dahongliutan deposit. We also dated one zircon U-Pb age of 211.6 ± 5.2 Ma from muscovite granite, two muscovite Ar–Ar ages of 179.6 ± 1.0 Ma and 174.3 ± 0.9 Ma, and one columbite–tantalite U-Pb age of 204.5 ± 1.8 Ma from spodumene pegmatites of the Zhawulong deposit. In addition, we dated one muscovite Ar–Ar age of 159.0 ± 1.4 Ma from spodumene pegmatite of the Ke’eryin deposit. Combining these ages and previous studies in chronology, we concluded that the granitic magma in the Jiajika, Xuebaoding, Dahongliutan, Zhawulong, and Ke’eryin deposits intruded into Triassic metaturbidites at approximately 223, 221, 220–217, 212, and 207–205 Ma, respectively, and that the crystallization of the corresponding pegmatite ceased at approximately 199–196, 195–190, 189–187, 180–174, and 159 Ma, respectively. In this study, we demonstrated that the peak in magmatic activity and the final crystallization age of the pegmatite lagged behind one another from the outer areas of the orogeny belt to the inner areas. The pegmatite–parented granitic magmas were sourced from Triassic metaturbidites that were melted by shear heating along the large-scale decollement resulting from Indosinian collisions along the North China block, Qiangtang–Changdu block, and Yangtze block. As a result, the above temporal and spatial regularities indicated that the tectonic–thermal stress resulting from the collisions of three blocks was transferred from the outer areas of the orogenic belt to the inner areas. A large amount of heat and a slow cooling rate at the convergent center of thermal stress in two directions will lead to crystallization and differentiation of magma in the Songpan–Ganzê orogenic belt, forming additional rare metal deposits.

The Lhasa terrane, forming one of the main tectonic components of the Himalayan–Tibetan orogen, has received a lot of attention as it records multiple episodes of plate spreading, subduction and collision within the realm of the Paleo-Tethys Ocean. A review of the mineralogical, petrological, geochemical and geochronological data of eclogites, associated blueschists and garnet-bearing mica schists from the Sumdo high- and ultrahigh-pressure metamorphic (HP/UHP) complex in the central/southern part of the Lhasa terrane, is present here so that the origin and tectono-metamorphic evolution of this important suture can be deduced. By re-evaluating the original published P – T conditions for the metamorphic rocks of the Sumdo Complex, we consider that the Sumdo Complex has experienced low temperature HP/UHP metamorphic conditions, characteristic of fast subduction (and exhumation) in a typical oceanic subduction zone setting. The original wide spread in the maximal peak P – T conditions could be reduced in size due to thus far unknown inconsistencies in the usage of applied geothermobarometric techniques. The remaining spread in the maximal P – T conditions ( c. 200°C/10 kbar) of the HP/UHP regions can be explained by a mechanism that the rocks from individual tectonic slices were subducted to different depths and followed by juxtaposition on their way back to the surface. A re-consideration of the isotopic ages of eclogites from the Sumdo Complex demonstrates that the opening of the Paleo-Tethys Ocean, located in between the two major components of the Lhasa terrane, was initiated prior to c. 280 Ma and the eclogite facies metamorphism is likely to be of late Permian ( c. 260 Ma) to early Triassic age (245–225 Ma), recording different ages of subduction from individual slices of the oceanic crust. The closure of the Paleo-Tethys Ocean resulted, no earlier than 210 Ma, in the final collision between the northern and southern Lhasa blocks. This final collision event may have been triggered by the initial subduction of the Bangong–Nujiang Tethys Ocean in the north.

The Jiajika rare-metal deposit located in western Sichuan Province (China) is renowned as the largest lithium deposit in Asia, and the No. 134 pegmatite dike is the largest lithium pegmatite under mining conditions in the area. On the basis of a detailed characterization of textures and minerals in the Jiajika No. 134 pegmatite, two zones (the barren Zone I and the spodumene Zone II) and three subzones (Zone II was subdivided into microcrystalline, medium-fine grained and coarse-grained spodumene zones) have been identified. The detailed mineralogical characteristics of lithium minerals and other indicator minerals from each zone were evaluated by EPMA for illustrating the magmatic–hydrothermal evolution and the cooling path of the Jiajika No. 134 pegmatite. From the outer zone inwards, grain size gradually increased, the typical graphic pegmatite zone was absent, and spodumene randomly crystallized throughout nearly the whole pegmatite body. This evidence indicated a Li-saturated melt prior to pegmatite crystallization, which could be the main cause of the super-large-scale Li mineralization of the Jiajika No. 134 pegmatite. A comparison of the Cs content between primary beryl in the Jiajika No. 134 pegmatite and other important Li-Cs-Ta pegmatites in the world indicates that No. 134 pegmatite shows a high degree of fractional crystallization. The evolution of mica species from muscovite to Li-micas from Zone I to Zone II marks the transition from the magmatic to the hydrothermal stage in pegmatite evolution. The absence of individual lepidolite and the relatively limited scale of alteration of spodumene (<10 vol%) suggest that the activity of the hydrothermal fluids in the system is limited, which contributes to the preservation of the easily altered Li ores and is also an important controlling factor of the super-large-scale Li mineralization of the pegmatite. Spodumene–quartz intergrowth (SQI) usually occurs partly along the rims of the spodumene grains in the Jiajika No. 134 pegmatite. Combined with the pegmatite mineral equilibria, the results of fluid inclusion studies of the pegmatite and the metamorphic conditions in the area, a constrained P-T path of the magmatic–hydrothermal crystallization of the Jiajika No. 134 pegmatite is proposed. The unusual steeply sloped cooling path of the No. 134 pegmatite could be attributed to the fast pressure drop triggered by the intrusion of a pegmatitic melt along the fractures surrounding the Majingzi granite, which could also be the dominant evolution process for other spodumene pegmatites with similar SQI features in the world. The feature of limited internal geochemical fractionation suggested by mineral-scale geochemical analyses of spodumene and micas, combined with the clear textural zoning of the No. 134 pegmatite, can best be ascribed to the effect of undercooling during pegmatite formation. This effect might be one of the non-negligible rules of pegmatite petrogenesis, and would significantly upgrade the potential of Li mineralization by minimizing diffusional Li transfer to the country rocks.

With the explosive growth in demand for lithium (Li) resources, the Mufushan area has been a hotspot for Li deposit exploration in China in recent years. Geochemical maps and geochemical anomaly maps are basic maps in the geochemical exploration of mineral resources. A fixed-value method to contour a Li geochemical map is presented here, in which Li concentrations are divided into 19 levels on 18 fixed values, ranging from 5 μg/g (corresponding to the detection limit) to 1858 μg/g (corresponding to the cut-off grade of Li deposit in hard-rock type) and illustrated in six color tones corresponding to Li areas of low background, high background, low anomaly, high anomaly, mineralization in clay-type, and mineralization in hard-rock type. The geochemical map of Li in the Mufushan area using the new fixed-value method indicates that the study area belongs to the high background area, and the known Li deposits are located in the high anomaly areas. In addition, the geochemical anomaly map of the Mufushan area is drawn using the method of seven levels of classification, and indicates that the known Li deposits are all in the anomaly areas, with anomaly levels not lower than the second level. Furthermore, four other areas are recognized for Li resource potential based on the geochemical map and geochemical anomaly map in the Mufushan area.

The No. 5 pegmatite vein is the most evolved and well mineralized vein in the Renli deposit, with beryl being the most important beryllium mineral. The vein represents one of the most important gem-quality aquamarine mines at Renli. In this study, beryl crystals from the No. 5 pegmatite vein were examined by EMPA (electron microprobe analysis), ICP-MS (inductively coupled plasma-mass spectrometry), XRD (diffraction of X-rays), FTIR (fourier transform infrared spectrometer), and Raman analyses. Field and petrographic observations showed that most beryl crystals are euhedral to subhedral with light to medium blue color. EMPA analyses indicated that the main chemical compositions of beryl are close to the ideal values, with relatively low Fe (0.222–0.690 wt%) and alkali metal (0.280–0.820 wt%) contents. Geochemical and spectroscopic analyses indicated that cations replacement in beryl is relatively simple. The substituting cations of beryl in the octahedral Al site include mainly: Mg²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Cr³⁺, Ti⁴⁺, and the excess Si. The tetrahedral Be site is mainly replaced by Li. Alkali metals in channel (esp. Na) serve as a charge compensator. According to the Fe-Mg-alkali and Li-Cs contents, the beryls from No. 5 pegmatite belong to the low Li-Cs and low Fe-Mg-medium alkali beryl groups. Field and geochemical data indicated that the No. 5 pegmatite vein formed by the multistage Mufushan granitic pluton emplacement and the magma source was less evolved.