Petrochemistry, U–Pb (zircon) age, and palaeotectonic setting of the Lampang volcanic belt, northern Thailand

Cretaceous (131–92 Ma) plutonic rocks intruded two different NW-SE–oriented belts of host rocks in the southernmost tip of the Peninsular Ranges Batholith. The western belt, which was likely close to the paleotrench, consists of Jurassic meta-igneous rocks with oceanic-arc affinity. Toward the continent, the eastern belt is composed of amphibolite, paragneiss and orthogneiss, schist, calc-silicate, marble, and undifferentiated metamorphic rocks, for which the sedimentary protoliths are interpreted as Triassic–Jurassic back-arc assemblages or Paleozoic continental slope and basin sediments. Here, we present U-Pb isotope data for detrital zircons from five paragneisses and two schists for maximum depositional age (MDA) and provenance analysis estimations. In addition, we obtained Sm-Nd isotope dilution–thermal ionization mass spectrometry isochron ages of leached garnet and whole-rock (WR) samples to establish the timing of metamorphism. Detrital zircon geochronology of three samples from the western belt and two from the eastern belt indicates Early Jurassic MDAs (193–177 Ma), whereas one sample from the western belt has a Late Triassic MDA (208 Ma), with zircon populations that were shed from similar sources. The compiled zircon data show four age modes, suggesting provenance from the Permian–Triassic Cordilleran arc and the Appalachian, Pan-African, and Grenville orogens. Based on these observations, we consider that the two proposed belts of host rocks from the southern Peninsular Ranges Batholith share a similar origin, where the sedimentary protoliths were deposited in ocean basins fed by continentally derived material with peri-Gondwanan affinity. One biotite-garnet paragneiss yielded a Sm-Nd garnet-WR age at 160 ± 2 Ma, coeval with metamorphic zircon growth (ca. 166 Ma) in the same sample, indicating a Middle–Late Jurassic metamorphic event. The other samples yielded Sm-Nd garnet-WR ages of 105 ± 3, 114 ± 2, and 214 ± 13 Ma. The Cretaceous ages are coeval with plutonism, whereas the Triassic age is the oldest metamorphic age documented in the Baja California Peninsula. The detrital zircon provenance ties the sedimentary protoliths to the ancient continental margin of Mexico since the Late Triassic. The Sm-Nd garnet-WR geochronology provides the first well-constrained dates for the timing of metamorphism in this region, which reveals not only a regional event, but also coeval metamorphism and magmatism.

Effect of high and low Nb content in multicomponent Nb–Ni–Ti–Zr–Co alloy on its structure, hardness and hydrogen permeability

Genesis of tin-dominant polymetallic deposits in the Dachang district, South China: Insights from cassiterite U–Pb ages and trace element compositions

Meso- to Neoproterozoic terrane accretion: Insights from juvenile mafic magmatism from the Votuverava Group and Embu Complex, southern Ribeira Belt, Brazil

The Nevadan orogeny was a very short-lived event in the Late Jurassic that involved the deformation of a great variety of rock types and Paleozoic and Mesozoic terranes throughout the extent of the Sierra Nevada. The Nevadan structures show great variation in style but relatively constant orientations. These relations can be explained by considering the prior histories of the various terranes. Slaty cleavages and tight folds are the characteristic main-phase structures in the western belt of Jurassic island-arc volcanic rocks and flysch-type sedimentary rocks. A strip of phyllites and greenschists along the eastern edge of the belt apparently represents similar Jurassic rocks that were deformed and metamorphosed at greater depths, probably during underthrusting of the western belt beneath the central belt. The central belt of Paleozoic metasedimentary and metavolcanic rocks shows the most extreme variation in style of main-phase structures, from weak, spaced to crenulation cleavages in the south, where polyphase deformed rocks formed a structural basement, to slaty and phyllitic cleavages and asymmetric to isoclinal folds in the north, where most of the Paleozoic basement rocks lack penetrative pre-Nevadan fabrics. Eastward-directed thrust faulting apparently was important only in the northern part of the range, where main-phase deformation was most intense. The eastern belt of Jurassic and Triassic magmatic arc-volcanic and sedimentary rocks defines the core of a major synclinorium, and the rocks contain penetrative slaty cleavages and asymmetric, tight to isoclinal folds. A late phase of Nevadan structures, consisting of northeast-trending cleavages and minor folds, also shows a marked variation in style, from relatively intensely developed in the north to very weakly developed in the south. The regional extent and geometry of the Nevadan structures indicate that the Nevadan orogeny involved underthrusting of island-arc rocks on the west and significant crustal shortening in the central and eastern belts. These features suggest that the Nevadan orogeny resulted from the collision of the island arc (western belt) with an andean-type arc (eastern belt) situated at the western edge of North America.

Crystallochemical indexes and geothermobarometric calculations as a multiproxy approach to P-T condition of the low-grade metamorphism: The case of the San Luis Formation, Eastern Sierras Pampeanas of Argentina

Trace-element characteristics and Pb isotopic evolution of metasediments and associated Proterozoic rocks from the amphibolite- to granulite-facies Bamble sector, southern Norway

Ratios of K2O : Na2O in Permian and Cretaceous basic igneous rocks of New Zealand show that two distinct belts of volcanic rocks can be defined in both the Permian and Cretaceous. In the Permian, a western belt, characterised by high K2O : Na2O ratios, can be traced along the western margin of the Southland — Key Summit and Nelson synclines, and an eastern belt, with low K2O : Na2O ratios occupies the eastern margin of these synclines. Close agreement of ratios between the Brook Street Volcanics and Eglinton Volcanics of the western belt, and the Lee River Group and Livingstone Volcanics of the eastern belt, supports correlation of these groups across the Alpine Fault.In the Cretaceous, a western belt, with high K2O : Na2O ratios can be traced from Mount Somers — Malvern Hills and Mandamus, to the Awatere Valley and Inland Kaikoura Range. An eastern belt extends from the Kaikoura coast through the eastern Wairarapa to East Cape.Comparison with present-day volcanic arcs shows similarities in the increase in K2O : Na2O ratios in going from the oceanic to the continental side of the arc. This supports the concept of a continental land mass to the west of New Zealand during the Permian and Cretaceous, and the existence of oceanic troughs to the east.

It was made an attempt to generalize geochemical data of Nb and Ta concentration in the most common igneous rocks of the Ukrainian Shield (USh). In the majority of widely distributed rocks of the USh (normal and subalkaline granitoids) the Nb and Ta concentration are similar to upper crust but lower the accepted Clark value for acidic rocks. In the more differentiated rapakivi granites concentrations of these elements reach or exceed the Clark’s concentrations (up to 35 ppm). Only highly differentiated alkaline rocks and alkaline feldspar granites (Perga, Kamiani mogyly, Ruska Poliana massifs) have high Nb concentrations (up to 800, 120 and 370 ppm, respectively). Medium rocks of the normal range are the least geochemically studied and typically are characterized low Nb and Ta concentrations. Almost all gabbroids as well as their metamorphosed analogues in the greenstone structures, are characterized by very low Nb (and Ta) concentration (two or more orders of magnitude) compared with Clark’s values for basic rocks (20 ppm Nb and 0.48 ppm Ta) according to A.P. Vinogradov. Against this background, increased of Nb and Ta concentration is observed in the main rocks of anorthosite-rapakivi-granite plutons. Howover even in these rocks concentration of these elements rarely reach or does not achieve the values which are typical for subalkaline and alkaline basalts of continental rifts. The regional heterogeneity in Nb and Ta distribution is observed in alkaline rocks of different composition: in the Azov Sea region these rocks are characterized by high concentrations, while in the western part of the USh the content of these elements is extremely low. The increased concentration of these elements is also revealed in kimberlites from the Azov Sea region and the Kyrovohrad megablock of the USh. The authors give some considerations and assumptions about the dependence on geochemical features of the Precambrian igneous rocks of the USh from the geodynamic conditions of their formation.

Nb-Ta systematics of Kohistan and Gangdese arc lower crust: Implications for continental crust formation

The gas-bearing areas in Poland are located on the northeast flank of the Carpathian Mountains, a region which extends geologically into Roumania. There are three belts in this province. About 100 oil-producing areas are scattered about in the two western belts, many of which also produce gas either with oil from common reservoir rocks or without oil from reservoir rocks above the oil-bearing series. Rocks of Cretaceous and Tertiary (Eocene) age produce oil and gas in the western (Median) belt. The Siary field produces gas and oil from rocks of Cretaceous age; Sekowa from Eocene and Cretaceous formations; and Potok from the Eocene. But the Sadkowa-Bialkowka-Brzezowka-Mecinka-Jaszczew fields (Jaslo district) produce only gas from rocks of Eocene age. The central belt (Marginal) produces oil and gas from rocks of Tertiary (Oligocene and Eocene) and Cretaceous ages; notably in the Boryslaw, Tustanowice, and Mraznica fields. Of these Mraznica ranks first. The eastern belt (sub-Carpathian) produces gas only from reservoirs in the upper part of the Miocene series at Daszawa and Kalusz. Wells have not been drilled deep enough to encounter rocks of Oligocene, Eocene, and Cretaceous age that are oil- and gas-bearing in the two western belts. Poland is primarily an oil-producing state. Natural gas has been produced in the Carpathian region of Poland since 1912. Most of the gas produced prior to 1916 was wasted to the atmosphere, but since 1916 increasing amounts have been used for fuel purposes. The longest gas pipe line extends from the Daszawa field to the city of Lwow, a distance of 100 kilometers (about 62 miles).

To understand the onset and evolution of cold subduction on Earth, detrital sedimentary rocks of Precambrian age, potentially derived from exposed high-P low-T metamorphic rocks can be investigated. This requires the estimation of peak metamorphic pressure and temperature, time of formation, and source lithology (P-T-t-X) of detrital single grains. Rutile is a common accessory mineral in subducted oceanic crust and one of the most likely minerals from subducted rocks to survive sedimentation processes. As single grain T-t-X estimates on rutile are possible, it is a prime candidate for the investigation of subduction processes through time.We developed a method to identify rutile formed in modern cold subduction conditions, by combining in-situ polarised Fourier Transform Infrared Spectroscopy (FTIR) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS).Our study reveals a pressure-dependent variation in hydrogen content within metamorphic rutile, ranging from less than 10 to 2500 μg/g H2O. Higher peak metamorphic pressures correspond to elevated H2O contents, particularly noticeable in mafic low-temperature eclogite facies rutile, suggesting H-in-rutile can be used as a pressure indicator. Using Zr in rutile as a temperature indicator, H2O/Zr ratios act as proxies for thermal gradients (P/T) in metamorphic rutile. When combined with low Nb, W, and Sn contents, typical of mafic protoliths, it is possible to identify modern-style cold subduction of mafic crust using trace element signatures in detrital rutile.Therefore, detrital rutile can serve as a tracer for subduction conditions over time, as modern-style cold subduction signatures are preserved in rutile during weathering and sedimentary processes.  In this study, we test our novel approach on detrital rutile grains of sandstones and arkoses from the Torridon and Ardvreck Groups, Hebridean in NW Scotland. Our analysis reveals that some grains of the Torridon Group of late Proterozoic age (detrital ages ranging from 1.0 to 1.9 Ga; Pereira et al., 2020) exhibit high H2O/Zr ratios and low total Nb+W+Sn contents, typical of low-T eclogite facies rutile. This implies that low-T eclogites which formed during cold subduction were likely exposed and eroded in the catchment of the sedimentary basins, indicating modern-style cold subduction during the Mesoproterozoic.  We propose that the combined measurement of H2O and trace elements in detrital rutile is a powerful tool to search for remnants of cold subduction through the Earth’s history. Pereira, I., Storey, C.D., Strachan, R.A., Bento dos Santos, T., Darling, J.R., 2020. Detrital rutile ages can deduce the tectonic setting of sedimentary basins. Earth Planet. Sci. Lett. 537, 116193. https://doi.org/10.1016/j.epsl.2020.116193

Thermal Evolution of Organic Matter and Secondary Hydrocarbon Generation from Upper Paleozoic Coal Deposits in Northern China

Mesozoic volcanic rocks in the lower reaches of the changjiang river

Abstract:The Langdu high–K calc–alkaline intrusions are located in the Zhongdian area, which is the southern part of the Yidun island arc. These intrusive rocks consist mainly of monzonite porphyry, granodiorite, and diorite porphyry. The K2O content of majority of these rocks is greater than 3%, and, in the K2O‐SiO2 diagram, all the samples fall into the high‐K calc‐alkaline to shoshonitic fields. They are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs; LaN/YbN= 14.3–21.2), and show slightly negative Eu anomalies (δEu = 0.77–1.00). These rocks have high K, Rb, Sr, and Ba contents; moderate to high enrichment of compatible elements (Cr = 36.7–79.9 ppm, Co = 9.6–16.4 ppm, and MgO = 2.2%‐3.4%); low Nb, Ta, and Ti contents, and characteristic of low high field strength elements(HFSEs) versus incompatible elements ratios (Nb/Th = 0.75, Nb/La = 0.34) and incompatible elements ratios (Nb/U = 3.0 and Ce/Pb = 5.1, Ba/Rb = 12.0). These rocks exhibit restricted Sr and Nd isotopic compositions, with (87Sr/86Sr)i values ranging from 0.7044 to 0.7069 and εNd(t) values from −2.8 to −2.2. The Sr‐Nd isotope systematic and specific trace element ratios suggest that Langdu high‐K calc‐alkaline intrusive rocks derived from a metasomatized mantle source. The unique geochemical feature of intrusive rocks can be modeled successfully using different members of a slightly enriched mantle, a slab–derived fluid, and terrigenous sediments. It can be inferred that the degree of partial melting and the presence of specific components are temporally related to the tectonic evolution of the Zhongdian island arc. Formation of these rocks can be explained by the various degrees of melting within an ascending region of the slightly enriched mantle, triggered by the subduction of the Garzê–Litang ocean, and an interaction between the slab–derived fluid and the terrigenous sediments.