The exposed meta-sedimentary rocks show higher K2O/Na2O and Al2O3/(Na2O+CaO) and lower Eu/Eu∗ than those occurring as xenoliths in the Yuhuashan volcanic-intrusive complex, indicating relatively strong weathering and leaching in the provenance area. These xenoliths from the mid-lower crust also have significantly high U contents. Consequently they probably are an important source for uranium in the XSYHS volcanic rocks. The Permo-Triassic time was characterized by the elimination of several oceanic domains, and the collision of volcanic arcs as the youngest ages of the detrital zircons suggest . Due to the obtained minimum Carboniferous ages of the detrital zircons in both terranes, the Gurvansayhan intra-oceanic volcanic arc and the Gobi Altai-Mandalovoo continental island arc appear to have collided with the Idermeg continental sliver in the Permian.

Reviews in Mineralogy and Geochemistry

The basement belongs to the pre-Cambrian Dogra Slates in the Kashmir basin, which are equivalent to the Hazara Formation, Manki Slates and Landikotal Slates. The cover sequence includes Early Paleozoic and Cenozoic rocks. Two major hiatuses exist in succession, one of them is at the boundary of basement rocks and cover sequence, and the other is between the Early Paleozoic and Cenozoic sequences.

Lab data acquisition and instruments

Fornelli, A.; Gallicchio, S.; Micheletti, F.; Langone, A. U–Pb detrital zircon ages from Gorgoglione Flysch sandstones in Southern Apennines as provenance indicators. The traditional petrography is widely applied to determine the composition of the sandstones and their provenance . The sandstone petrography was used to supplement the detrital zircon U-Pb age data in this study. A total of five sandstone samples from the entire section were selected for sandstone petrography. Thin sections of the samples were prepared in the Rock Cutting and Thin section lab at the Department of Earth Sciences, COMSATS University Islamabad, Abbottabad Campus, Pakistan.

Contributions to Mineralogy and Petrology

The routine practice in geology of enforcing stratigraphic order in interpretation of the ages of deposits from MDAs is inherently Bayesian. Building this knowledge into a statistical model can provide a cascade of information through series of samples that can improve our characterization of geologic histories. Detrital zircons from three sandstone samples of the Ruyang Group yield 207Pb/206Pb ages ranging from 1.70Ga to 2.70Ga with two pronounced peaks at ca. A weighted mean age at 1744±22Ma from nine young zircon ages between 1.80Ga and 1.70Ga can constrain the maximum depositional age of the Ruyang Group. Most detrital zircons exhibit negative ɛHf values ranging from −15.6 to 0 and old TDMC ages ranging from 2.50Ga to 3.60Ga, implying reworking of Archean crust.

Figure 4.Plots of log(SiO2/Al2O3) versus log(Na2O/K2O) after , log(SiO2/Al2O3) versus log(Fe2O3/K2O) after , and CIA versus WIP after for siliciclastic rocks of the Chiron Basin. Figure 2.Geological map of the western part of Chiron Basin (after and our data). Kotov, A.B.; Salnikova, E.B.; Kovach, V.P.; Velikoslavinsky, S.D.; Sklyarov, E.V.; Gladkochub, D.P.; Larin, A.M.; Tolmacheva, E.V.; Fedoseenko, A.M.; Plotkina, Yu.V. The Younger Age Limit of Metasedimentary Protolith Formation of the Lower Part of the Udokan Group Rocks . Jacobsen, S.; Wasseburg, G. Sm-Nd isotopic evolution of chondrites and achondrites. Zaika, V.A.; Sorokin, A.A.; Xu, B.; Kotov, A.B.; Kovach, V.P. Geochemical Features and Sources of Metasedimentary Rocks of the Western Part of the Tukuringra Terrane of the Mongol–Okhotsk Fold Belt. The reported study was funded by RFBR according to the research projects number 18−35−20004 and 18−05−00840.

Adopting the multiple-etch technique of Naeser et al. , five mounts per sample were etched in a eutectic melt of NaOH and KOH at 228 °C for either 14 or 21 h. Mica laminae were attached to the samples as external detectors. The mounts were irradiated at the Radiation Center of Oregon State University, using a nominal neutron fluence of 1 × 1015 ncm−2.

The modeled ages for all units are limited to fairly precise ranges (95% credible intervals span ~3-4 Ma) despite limited absolute age constraints. As was highlighted by Figures 5C,D, this is a function of the strong age constraints that are available within this section. At the base of the section, the high-precision ID-TIMS date (Daniels et al., 2018a) provides a narrow range of allowable ages, and the identified fossil assemblages (Schwartz et al., 2017) provide lower limits to depositional ages close to the MDAs. The choice of a linear sediment accumulation rate is arbitrary, and it is easy to see from Figure 1 how this can cause problems. For example, a period of non-deposition between Unit 1 and Unit 0 in Figure 1A seems to best describe the observed ages of these units.

Depending on the detrital zircon study, there should be different variables included for analysis. There are two main types of data, analyzed zircon data (quantifiable data and imagery/descriptive data), and sample data. Although the original purpose of the megalithic jars remains to be determined, the present research indicates a long history of activity at the sites. The evidence provided by OSL dating has provided the first ever dates for the original placement of the jars at Site 2–1240 BC to 660 BC. While the broad similarity in megalith morphology across Laos might suggest contemporaneity and the expression of a unique, yet to be identified, cultural group, more research needs to be conducted. Future studies might usefully be directed at obtaining further samples from under, and at the sediment-artefact interface with the megalithic jars, at other sites and from across the geographic extent of the culture, using OSL to refine the earliest jar emplacement date.

A simplified geological sketch of the Carpathian chain within Europe; generalized cross-section through the Western Carpathians (modified from ); the simplified geological map of the Outer Western Carpathians and the study area with the locations of the sampling point. Plašienka, D. Jurassic syn-rift HornyMatches and Cretaceous syn-orogenic, coarse-grained deposits related to opening and closure of the Vahic Ocean in the Western Carpathians—An overview. Mazur, S.; Aleksandrowski, P.; Turniak, K.; Awdankiewicz, M. Geology, tectonic evolution and Late Palaeozoic magmatism of Sudetes—An overview.

Dark brown particles represent siderophile elements that sink to the centre of Earth during core formation while the orange lithophile elements do not. Is the initial ratio of the two isotopes when the sample is formed. Is the measured ratio of the two isotopes of the sample.

Finally, the prepared samples were polished to make the surface of the grains smooth. Detrital zircons are those that have weathered out of the parent igneous or metamorphic rock and these can be found in sediments just about everywhere. These zircons are often analyzed by quantitative analysis. For example, a bucket of sand is extracted from a river or ancient lake bed and the results of all the ages of the zircons therein are plotted on the same graph. The peaks showing the most numerously computed ages are compared with possible igneous or metamorphic sources for the sediment.

An assessment of the discrepancy between bulk-mounted and handpicked zircons can therefore be used to evaluate the degree of representativeness of handpicked grains. These results highlight the importance of minimizing sample handling steps whenever practicable. Zircon bulk-mounting is the preferred approach for detrital zircon geochronology studies reliant on representative age distributions. Grain size could cause misinterpretation of provenance studies.

The western Central Asian Orogenic Belt: a window to accretionary orogenesis and continental growth

Consideration of regional north-to-south eolian sediment transport of Appalachian-derived sand to the Grand Canyon (Gehrels et al., 2011) suggests that other alternatives for sources of the sediment could be linked by multi-element dispersal systems. The Grenville-age zircons that are common in the Mississippian to Permian strata in the Grand Canyon could have been recycled from Neoproterozoic–Cambrian sandstones in northwestern Laurentia (e.g., Rainbird et al., 1992; Stewart et al., 2001; Mueller et al., 2007). Alternatively, the well-documented southward wind transport might reflect local reworking along coastal dunes of lithic and muddy sands of the distal Cutler Group from the Ancestral Rocky Mountains (e.g., Baars, 1988). Alternative depositional histories could also explain the observed geochronology. One such explanation would be the presence of an unconformity at approximately 1,670 m , above and below which point all geochronologic constraints could be described by a near-instantaneous rate of deposition .

Only concordant ages are considered and also small error ellipses situated close and only below the concordant age curve . Figure 7.Probability diagrams showing age distributions of detrital zircons from Aga–Borshchovochnyi metamorphic complex and ciliciclastic rocks of the Chiron Basin. Data from Supplementary Table S2; Aga-Borshchovochnyi metamorphic complex, Khara-Shibir Formation, Shazagaitui Formation, Zhipkhoshi Formation. Combining the new data with regional geological data suggests that sedimentary rocks of the Chiron Basin likely formed in a back arc basin setting on the southern periphery of the Siberian Craton facing the Paleozoic Mongol–Okhotsk Ocean. This supports an interpretation in which Archean, Paleoproterozoic, Neoproterozoic, and Cambrian zircons of the Aga–Borshchovochnyi metamorphic complex and Khara–Shibir, Shazagaitui, and Zhipkhoshi formations were derived from the same source.

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