http://www.geology.wisc.edu/~johnf/g777/Misc/Montel-1996.pdf

Electron microprobe dating of monazite

The early Paleozoic Wuyi-Yunkai orogen in South China is a major orogenic belt in East Asia that formed at a similar time as the classic Caledonian orogeny in Europe. Despite the possibility of its being one of the few examples of intraplate orogenesis in the world, details about the orogen remain poorly defined. In this study, we provide age constraints on metamorphic and magmatic events in the eastern segment of the orogen, and the protoliths of the amphibolite-facies metamorphic rocks found there. By combining previous work with our new metamorphic and petrogenetic analyses, we present the following findings: (1) the Wuyi-Yunkai orogeny occurred between mid-Ordovician (>460 Ma) and earliest Devonian (ca. 415 Ma) time; (2) amphibolite-facies metamorphism in the eastern Wuyi-Yunkai orogen occurred between ca. 460 and 445 Ma, whereas cooling below 500–300 °C occurred by ca. 420 Ma; (3) the orogen exhibits a clockwise pressure-temperature ( P - T ) path and a maximum pressure of >8 kbar, indicating crustal thickening during the orogeny; (4) protoliths of the high-grade metamorphic rocks in the eastern segment of the orogen were dominantly Neoproterozoic (840–720 Ma) volcanic and volcaniclastic rift successions and younger deposits formed in a failed rift, and Paleoproterozoic rocks account for only a small proportion of the outcrops; and (5) the analyzed granites indicate a mixed source of Paleoproterozoic basement and Neoproterozoic continental rift rocks, with elevated melt temperatures of >800 °C, which are interpreted as reflecting dehydration melting of basin sediments taken to below midcrustal levels.

Magmatic and metamorphic events during the early Paleozoic Wuyi-Yunkai orogeny, southeastern South China: New age constraints and pressure-temperature conditions

The radiogenic isotope composition of dissolved trace metals in the ocean represents a set of relatively new and not yet fully exploited tracers with a large potential for oceanographic and paleoceanographic research on timescales from the present back to at least 60 Ma. The main topic of this review are those trace metals with oceanic residence times on the order of or shorter than the global mixing time of the ocean (Nd, Pb, Hf, and, in addition, Be). Their isotopic composition in the ocean has varied as a function of changes in paleocirculation, source provenances, style and intensity of weathering on the continents, as well as orogenic processes. The relative importance of these processes for each trace metal is evaluated, which is a prerequisite for reliable interpretation of their time series in terms of changes in paleocirculation or weathering inputs. This analysis of processes includes a discussion of the long-term isotopic evolution of Sr and Os, which are well mixed in the ocean and have thus not been influenced by circulation changes. The radiogenic isotope evolution of those trace metals with intermediate oceanic residence times can be used as paleoceanographic proxies to reconstruct paleocirculation and weathering inputs into the ocean. This is demonstrated by studies from different ocean basins, mainly carried out on ferromanganese crusts, which show that radiogenic trace metal isotopes provide important new insights and can complement results obtained by other well-established paleoceanographic tracers such as carbon isotopes.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000RG000094

Radiogenic isotopes: tracers of past ocean circulation and erosional input

The Early Triassic Indosinian orogeny in Vietnam (Truong Son Belt and Kontum Massif); implications for the geodynamic evolution of Indochina

https://www.lancaster.ac.uk/staff/najman/Najman%20ESR%202006.pdf

The detrital record of orogenesis: A review of approaches and techniques used in the Himalayan sedimentary basins

The Kontum massif of south‐central Vietnam has long been classified as lower continental crust of Precambrian (Archean) age. U‐Pb zircon and 40Ar/39Ar biotite ages from charnockites and amphibolite facies rocks from this basement, however, yield much younger ages and imply at least two Paleozoic thermal events. Syntectonic charnockites from the Kannack complex and the southern Kontum massif record Permo‐Triassic magmatism (U‐Pb: \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $249\pm 2$ \end{document} [2σ] Ma and \docume...

/pdf/geodynamic-significance-of-the-kontum-massif-in-central-1mrpzn1x3z.pdf

Geodynamic Significance of the Kontum Massif in Central Vietnam: Composite 40Ar/39Ar and U‐Pb Ages from Paleozoic to Triassic

U-Pb dating on zircon and monazite from different varieties of leucogranites in the Karakoram Batholith reveals two distinct pulses of plutonism at 25.5 +0.3/-0.8 and 21.4 +0.3/-0.6 Ma. In both granites, these minerals contain inherited components, documenting the presence of Precambrian material in the magma source. A crustal origin of the granites, and long crustal residence times of the source rocks are confirmed by highly negative $$\epsilon _{i}^{Nd}$$, strongly positive $$\epsilon _{i}^{Sr}$$, and $$T_{DM}^{ND}$$ in excess to 1 Ga. A biotite gneiss and a granitic dike from the Karakoram Metamorphic Complex south of the batholith yield very similar $$\epsilon _{i}^{Nd},\epsilon _{i}^{Sr}, T_{DM}^{ND}$$. In a Pb evolution diagram, initial isotopic compositions for both the granites and the rocks from the metamorphic complex plot far above the reference field for MORB documenting very close affinity to the Eurasian (Tibetan) continental crust. The striking similarity of isotope signatures between leuco...

Urs Schärer

Papers

Geodynamic Significance of the Kontum Massif in Central Vietnam: Composite 40Ar/39Ar and U‐Pb Ages from Paleozoic to Triassic

Age, Cooling History, and Origin of Post-Collisional Leucogranites in the Karakoram Batholith; A Multi-System Isotope Study