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The carbonate clumped isotope (Δ47) thermometer has been widely used for paleoclimatic and paleo‐elevation reconstructions in sedimentary basins. Its reliable use requires that carbonates are free from later diagenetic alteration and retain their depositional Δ47 compositions, which is not always the case during the burial history of a basin. Therefore, identifying the alteration mechanisms that occurred during burial is essential for the correct interpretation of Δ47 signatures. In this study, we used the Δ47 thermometer to investigate possible carbonate alteration during burial of the Fenghuoshan Group (FHSG) in the Hoh Xil Basin, northern Tibetan Plateau, China. The Δ47 temperatures [T(Δ47)] of 30 carbonate samples through the ∼4.5 km thickness of the FHSG range from 51 to 132°C and exceed the surface temperature, implying the effects of thermal alteration on FHSG carbonates. The T(Δ47) values combined with the water‐rock exchange model, indicating that the alteration occurred under closed burial conditions at low water:rock ratios. The solid‐state reordering model fails to predict the Δ47 values, even with a modified time‐temperature history. In contrast, most measured Δ47 values are in agreement with predictions from recrystallization models. Therefore, the proposed alteration scenario is that FHSG carbonates underwent progressive microscale recrystallization during deep burial and subsequent exhumation, during which process recrystallized carbonate equilibrated with ambient burial temperature and therefore modified Δ47 values. This study highlights the potential of Δ47 thermometry and related models for evaluating the burial history and diagenesis of carbonates in sedimentary basins. Plain Language Summary: Carbonate clumped isotope composition (defined as Δ47) refers to the abundance of 13C–18O bonds in the carbonate, which is solely temperature dependent. This temperature dependence makes Δ47 a useful tool that can be used to obtain the carbonate formation temperature. However, the original Δ47 composition could be altered by either solid‐state reordering of C–O bonds or carbonate recrystallization during the burial history of sedimentary basin. Discriminating which alteration occurred during burial process is essential for the correct interpretation of Δ47 signature and the burial history. In this study, we measured Δ47 values of Fenghuoshan Group (FHSG) carbonates in the Hoh Xil Basin, northern Tibetan Plateau, China, and investigated their alteration during the burial history of FHSG by using the solid‐state reordering and recrystallization models. Our results indicate that FHSG carbonates underwent progressive microscale recrystallization during deep burial history, and the recrystallized carbonates recorded modified higher Δ47 temperatures. This study highlights the potential of Δ47 thermometry and related models for evaluating the burial history of sedimentary basins. Key Points: Clumped isotope temperatures of 51–132°C reflect thermal alteration during the burial history of the Fenghuoshan Group (FHSG)The alteration of FHSG carbonate Δ47 occurred in a late‐burial environment at a low water‐rock ratioFHSG carbonate underwent microscale recrystallization during burial and exhumation and eventually recorded high T(Δ47) [ABSTRACT FROM AUTHOR]

Early Cenozoic plate collision of India and Eurasia was a significant geological event, which resulted in Tibetan Plateau (TP) uplift and altered regional and global atmospheric circulations. However, the timing of initial collision is debated. It also remains unclear whether the TP was deformed either progressively northward, or synchronously as a whole. As the largest basin in the hinterland of the TP, evolution of the Hoh Xil Basin (HXB) and its structural relationship with development of the Tanggula Thrust System (TTS) have important implications for unraveling the formation mechanism and deformation history of the TP. In this study, we present results from a long sedimentary sequence from the HXB that dates the Fenghuoshan Group to ∼72–51 Ma based on magnetostratigraphy and radiometric ages of a volcanic tuff layer within the group. Three depositional phases reflect different stages of tectonic movement on the TTS, which was initialized at 71.9 Ma prior to the India–Eurasia collision. An abrupt sediment accumulation rate increase from 53.9 Ma is a likely response to tectonic deformation in the plateau hinterland, and indicates that initial India–Eurasia collision occurred at no later than that time. This remote HXB tectonosedimentary response implies that compressional deformation caused by India–Eurasia collision likely propagated to the central TP shortly after the collision, which supports the synchronous deformation model for TP. [ABSTRACT FROM AUTHOR]

We present a first combined environmental magnetic and geochemical investigation of a loess–paleosol sequence (<55 ka) from the Chuanxi Plateau on the eastern margin of the Tibetan Plateau. Detailed comparison between the Ganzi section and the Luochuan section from the Chinese Loess Plateau (CLP) allows quantification of the effects of provenance and climate on pedogenic magnetic enhancement in Chinese loess. Rare earth element patterns and clay mineral compositions indicate that the Ganzi loess originates from the interior of the Tibetan Plateau. The different Ganzi and CLP loess provenances add complexity to interpretation of magnetic parameters in terms of the concentration and grain size of eolian magnetic minerals. Enhanced paleosol magnetism via pedogenic formation of ferrimagnetic nanoparticles is observed in both sections, but weaker ferrimagnetic contributions, finer superparamagnetic (SP) particles and stronger chemical weathering are found in the Ganzi loess, which indicates the action of multiple pedogenic processes that are dominated by the combined effects of mean annual precipitation (MAP), potential evapotranspiration (PET), organic matter and aluminium content. Under relatively high MAP and low PET conditions, high soil moisture favours transformation of ferrimagnetic minerals to hematite, which results in a relatively higher concentration of hematite but weaker ferrimagnetism of Ganzi loess. Initial growth of superparamagnetic (SP) particles is also documented in the incipient loess at Ganzi, which directly reflects the dynamic formation of nano-sized pedogenic ferrimagnets. A humid pedogenic environment with more organic matter and higher Al content also helps to form finer SP particles. We therefore propose that soil water balance, rather than solely rainfall, dominates the type, concentration and grain size of secondary ferrimagnetic minerals produced by pedogenesis. [ABSTRACT FROM AUTHOR]

High-resolution environmental records from the Tibetan Plateau are essential to understand past global climatic and environmental changes. Magnetic minerals in lake sediments are important proxies to reconstruct environmental and climatic changes. Nam Co (lake) is a typical great lake in the transitional region of southwest monsoon in the Tibetan Plateau. Previous studies have extensively focused on geochemistry, microfossils, sedimentology and biochemistry analysis of Nam Co, which provides sound interpretation of paleoclimatic and paleoenvironmental changes. However, up to now, no systematic environmental magnetic studies have been carried out. Therefore, high-resolution and systematic magnetic studies combined with geochemical parameters were carried on lake sediments of core NC 08/01 from Nam Co for the Holocene period (11.3 cal ka BP) in order to explore how magnetic properties of the sediments respond to climatic changes. Based on variations of magnetic proxies, the sequence can be separated into 3 units. Unit 1 (236-199 cm, 11.3-7.8 cal ka BP) contains dominantly coarse-grained magnetite with homogeneous grain size. A positive correlation between magnetite and Ti strongly suggests that these coarse-grained detrital magnetites reflect detrital input signals due to insignificant effects of postdepositional dissolution processes on these coarse-grained magnetite particles. For Unit 2 (198-102 cm, 7.8-2.1 cal ka BP), magnetic grain size is finer and the corresponding concentration of magnetite is also reduced. This is mainly due to significant dissolution of these fine-grained detrital magnetite particles, which were transported under reduced water flow conditions during this period. For Unit 3 (101-0 cm, 2.1-0 cal ka BP), the bulk magnetic properties are dominated by a mixture of single domain biogenic magnetite and detrital magnetite. The concentration of magnetic minerals is not correlated with the Ti content. In conclusion, the preservation of magnetic minerals in the lake sediment and thus the corresponding magnetic properties are related to the initial grain size. Combination of magnetic properties (including variation of grain size and concentration) and other proxies of detrital inputs (e.g. Ti) can be used to infer the variation of redox conditions in Nam Co. These results provide a viable framework for reconstructing the paleoenvironmental changes of this lake. [ABSTRACT FROM AUTHOR]

Insoluble microparticles in ice cores are related closely to the transportation of eolian dust, and thus are important natural media to reconstruct climate change. In this study, we conducted a systematic mineral-magnetic investigation of insoluble microparticles in the Nojingkangsang ice core (29°2.1′N, 90°11.88′E, 5950 m) from the Southern Tibetan Plateau. Results indicate that the dominant magnetic mineral is magnetite, and its concentration has grown significantly since the 1980s, which coincides with trends in climate warming of the Tibetan Plateau. Influenced by regional warming, the glacial recession around Nojingkangsang shortens the distance between the dust source and glacial areas and thus increases the concentration of coarse-grained magnetic minerals in ice cores. However, the frequency of dust storms, associated with annual precipitation, could play only a regulatory role on the magnetic content over yearly (or seasonal) time scales. Therefore, using a new approach, the magnetic index of insoluble microparticles in ice cores of this region is seen as mainly reflecting trends in climate warming. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution proxy records from Tibetan Plateau are essential to understand the past climatic and environmental changes. In this work, we conducted systematic environmental magnetic studies on lacustrine sediments from Lake Pumoyum Co, southern Tibet, spanning from the last deglaciation (~19ka) to present. We correlated the magnetic proxies in the lake core with environmental changes. The magnetic proxies from the 3units were studied. Both Unit 3 (19–13.2ka) and Unit 2 (13.2–8.4ka) contain evidences for an anoxic or sub-anoxic environment. Fine-grained greigite dominates the bulk magnetic properties of Unit 3, while both magnetite and greigite coexist in Unit 2. Overall, this reveals a transition from an anoxic environment to an oxic environment. In contrast, Unit 1 (8.4ka–present) spans the Holocene when the lake environment was oxic. There is an increasing trend in the concentration of magnetic minerals, which reflects an increasing transport of magnetic minerals from the catchment into the lake due to the increased post-glacial melt-water flow. Although different mechanisms affect the magnetic assemblage and associated magnetic properties in the different units, our results suggest that the magnetic proxies of the local lake environment on southern Tibet are sensitive to environmental changes. [Copyright &y& Elsevier]

The extent to which ore bodies are preserved in orogenic belts remains a poorly understood area of ore deposit research. Using zircon and apatite fission track analysis together with apatite (U-Th)/He dating we constrained the erosion history of the ore bodies in the Harizha–Halongxiuma mining area of the East Kunlun Range, Northern Tibetan Plateau, China. Apatite fission-track ages range from 114 ± 8 to 87 ± 6 Ma, with mean track lengths varying from 11.4 ± 1.9 to 12.9 ± 2.0 μm. Zircon fission-track ages vary from 205 ± 14 to 142 ± 7 Ma. In addition, apatite (U–Th)/He dating yielded ages of 60–56 Ma. The thermal history of Jiapigou was modelled based on the apatite fission-track data, including ages and track lengths, with constraints of zircon fission-track ages and (U-Th)/He ages. The exhumation history of the Harizha–Halongxiuma mining area was reconstructed with these age data, revealing that since the early Mesozoic the area has undergone three cooling stages: (1) rapid cooling from 175 ± 30 Ma to 100 ± 10 Ma with a cooling rate and inferred exhumation of 2.0 ± 0.8 °C/Myr and 4.3 ± 1.7 km, respectively; (2) a relatively stable stage from 100 ± 10 Ma to 40 ± 10 Ma with a cooling rate and inferred exhumation of 0.3 ± 0.1 °C/Myr and 0.5 ± 0.2 km, respectively; and (3) rapid cooling since 40 ± 10 Ma with a cooling rate and inferred exhumation of 1.2 ± 0.6 °C/Myr and 1.4 ± 0.4 km, respectively. This exhumation history is consistent with the subduction process of Pacific plate and the strike slip movements of Dunmi fault. The total exhumation after main mineralization is calculated to be 7.6 ± 3.2 km, suggesting that ore bodies in the Harizha–Halongxiuma mining area remain partially preserved. [ABSTRACT FROM AUTHOR]