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Thermal history modeling based on low-temperature thermochronological data is widely used in the study of geology. Despite its common applications, several problems remain easy to ignore yet should not be overlooked in the execution of such models. This paper describes four key problems of thermal history modeling, namely, (1) is the best-fit thermal history the best? (2) Is the date constraint box a suitable constraint? (3) Does the bimodal distribution of the apatite fission track confined track length absolutely correspond to the cooling reheating model? (4) Is the whole thermal history path credible? Counterexamples are then provided to stress the importance of accounting for these problems in the application of thermal history modeling. Acknowledging the uncertainty and considering the geological constraints are recommended to improve the accuracy of thermal history models. Moreover, thermal historical intervals with high credibility and strong constraint ability are recommended to interpret the selected geological phenomenon. [ABSTRACT FROM AUTHOR]

Low temperature thermochronology plays a key role in the study of the tectonic evolution of the upper crust. History modeling of apatite fission-track requires the apparent age and the confined track-length distribution of spontaneous tracks. Obtaining length data does not require either thermal neutron irradiation or LA-ICP-MS measurements of the uranium content of the grains. This paper attempts to decouple the apatite fission-track age from the apatite fission-track length, but to combine the fission-track lengths with the respective apatite U-Th/He age to model the thermal history. The experiments were designed and conducted using a new Mathematica® modeling software "Low-T Thermo". Results of this modeling show that the thermal history modeling of apatite U-Th/He and fission-track ages can constrain the apatite fission-track length thermal history in the He partial retention zone and fission-track partial annealing zone, respectively. It implies that this combination of apatite fission-track length and apatite U-Th/He age has not been implemented before but is presented here as an alternative way of determining thermal histories without the addition of apatite fission-track age. [ABSTRACT FROM AUTHOR]

The timing of fault activity is a concern for geologists. This study used zircon U-Pb and apatite fission-track dating of fault breccia to determine the upper and lower limits for the time of faulting. The Guangsan fault in South China was taken as an example, and zircon U-Pb and apatite fission-track thermochronology were applied to the surrounding rock and fault breccia. The surrounding rock and fault breccia demonstrated 74.9–91.8 Ma and 73.9–93.5 Ma zircon U-Pb dates, respectively, indicating that the breccia formed after 73.9 Ma. They also demonstrated 71.6 ± 7.3 Ma and 85.9 ± 8.2–65.5 ± 6.5 Ma fission-track dates, implying that the fault breccia samples likely formed before ~70 Ma. Their thermal histories were highly consistent: both showed rapid cooling during 70–65 Ma and slow cooling during 65–0 Ma, implying that the fault was likely still active during 70–65 Ma, resulting in the rapid exhumation. [ABSTRACT FROM AUTHOR]

Bedding orientation measurement is a remote sensing application used in the field of geology, but the results are often unsatisfactory when the bed is dislocated along the strike direction. This paper proposes a new method called multiple-line method that is designed to improve bedding orientation measurement. This technique uses the bed as a vector, and fits the vectors as a plane to obtain the bedding orientation. This study employs the case of Yili Basin and measures 25 bedding orientations using the multiple-point and multiple-line methods, respectively. The result shows that the errors from the multiple-line method are mostly smaller than those from the multiple-point method when a bed is discontinuous. [ABSTRACT FROM AUTHOR]

The Eastern Guangxi area locates in the southwestern part of the transition zone between Yangtze and Cathaysia blocks, which is an important region because the boundary between two blocks probablycrosses there. We determined LA-ICPMS U-Pb ages for detrital zircons extracted from three sandstone samples in the Sinian-Cambrian strata in this region. The resulting ages are in the range of the Archeozoic and Neoproterozoic, with three notable concentrates at 991 Ma, 974 Ma, and 964 Ma, all of which are coeval to the Grenvillian magmatic activity. The new age distribution is similar to the data reported in the Precambrian strata of the adjacent southwestern Cathaysia Block, suggesting that most of our detrital zircons are likely derived from the Cathaysia Block. Combined with others' research, we are more inclined to accept the opinion that there was not an ocean basin between the two blocks during the Sinian-Cambrian period in Eastern Guangxi area if the timing of collision is the Early Neopro-terzoic. But if the timing of collision is the Early Paleozoic, we conclude that Luzhai uplift (i.e., the uplift between Guilin-Yongfu faultand Lipu fault) beyond the west of Dayaoshan regoin might be one part of southwestern sedimentation boundary of Cathaysia Block and Yangtze Block. We also get a few of detrital zircons with ages of ~590 Ma which probably sourced from northeastern Gondwana and 13 detrital zircons with over 3 000 Ma U-Pb ages which record the early formation of the earth. [ABSTRACT FROM AUTHOR]

The traditional paleotopographic explanation of mountain belts from low-temperature thermochronology is based on the simulation of low-temperature age data, the main defect of which is that we cannot make comparisons at the same time between the samples. In this article, we intend to make paleotopographic reconstruction on the basis of thermal history modelling. We first digitalize the thermal history curve and take contemporary temperatures for comparison, then reconstruct the paleotopography according to the distribution of the samples' temperatures. The finite difference method is used to solve the diffusion equation for heat in the reconstruction process. Our paleotopography reconstruction method can restore the topography over time. However, due to the nature of thermal history modeling and the noise in the data, the accuracy of this reconstruction is currently limited. [ABSTRACT FROM AUTHOR]

While the high-temperature exhumation process in the Dabie Mountain has been well documented, the low-temperature exhumation of this area since Cretaceous, especially since Late Cretaceous, is relatively less studied. Low-temperature thermochronology provides one of the important approaches to solve this problem. Based on the data of fission track and (U-Th)/He analysis of apaptites and zircons from the granitoid and metamorphic rocks in the Dabie Mountain, this paper applies Mancktelow’s and Braun’s methods to estimating the exhumation rates and to drawing the regional differential exhumation pattern since Cretaceous, especially since Late Cretaceous by taking into consideration factors such as heat transport, heat advection, topography and heat production, which could influence geothermal field in the shallow crust. Since Cretaceous, the exhumation rate (0.08–0.10 km/Ma) in the region around Tiantangzhai and in the south of Tanlu fault zone is larger than the rate (0.04–0.07 km/Ma) in other areas of the Dabie Mountain. The regional differential exhumation pattern might be related to the push-up effect caused by differential strike-slip movement along NNE-trending faults. [ABSTRACT FROM AUTHOR]

Migmatites record crucial information about the rheology and tectonothermal evolutionof the deep crust during orogenesis. In the Wuyi–Yunkai orogen in South China, migmatites at Fuhuling record Early Paleozoic high temperatures and associated partial melting. However, the absolute timing and implications for the rheology of the deep crust during orogenesis are poorly constrained. In this contribution, we used spatial analysis of migmatitic leucosomes, structural analysis, and U-Pb geochronology of zircon to elucidate the absolute timing of crustal partial melting, the degree of partial melting, and the role of partial melting on the rheology of the crust during the Wuyi–Yunkai orogeny. Partial melting of the Fuhuling migmatites occurred at c. 440 Ma during Early Paleozoic Wuyi–Yunkai orogenesis. Subsequent lower temperature metamorphism associated with Indosinian movement that caused minor zircon recrystallization was temporally associated with the crystallization of nearby biotite monzogranites, but it did not influence the morphology of the Fuhuling migmatites. The migmatites preserve a morphological transition from metatexite to diatexite with an increasing proportion of leucosome. This transition preserves different structural characteristics that represent the response of the solid framework and melt network to variable melt fractions during partial melting. The large proportion of in situ or in source leucosome in the Fuhuling migmatites suggests that it was a melt-rich crustal horizon during orogenesis, and that a substantial proportion of anatectic melt was retained in the deep crust. The rheological transition documented in the Fuhuling migmatites was caused by changes in the melt fraction, and it is an analogue for the rheological transition characteristics of melt-rich crustal horizons in the Yunkai region during Early Paleozoic Wuyi–Yunkai orogenesis and subsequent orogenic collapse. [ABSTRACT FROM AUTHOR]