State Key Laboratory of Isotope Geochemistry

This article presents a high precision method for Ba isotope measurements using multiple-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS).

This study provides a method for measuring Pb isotopes of olivine-hosted melt inclusions with diameters larger than 40 micrometers.

Zircon water content is an important physicochemical parameter for many geological processes, yet its measurement by the secondary ion mass spectrometry (SIMS) technique is hampered by the lack of suitable reference materials and high water background, especially if large-geometry (LG)-SIMS is used.

Secondary ion mass spectrometry (SIMS) has been applied to analyze a wide range of materials for earth science research due to its high sensitivity, high precision and capacity for <italic>in situ</italic> micro-analysis.

Magnetic graphene nanocomposite was fabricated and applied to the extraction of PAHs in water, followed by GC-MS. The method showed a good linearity. The limits of detection (S/N = 3) were in a range between 0.02–14.3 ng L⁻¹.

We propose a “peak cut” procedure of column separation for calcium isotope measurement using the double spike technique and thermal ionization mass spectrometry (TIMS).

Separating Ti from matrix elements with Ln-spec and AG50W-X12 resins.

This study investigates the double spike (DS) proportion effect on measurements of stable Zn, Mo, Cd, and Sn isotopes by multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS).

A chromatographic procedure for Rb, K, Ba and Sr one-by-one separation from geological materials has been developed by using a single column with packing Sr-spec resin, followed by high-precision Rb isotope measurement by MC-ICP-MS.

Mesozoic A-type granites are widely distributed in the Lower Yangtze River Belt (LYRB) in China, but their petrogenesis and geodynamic settings are unresolved. Here, we describe geochronological and geochemical study of granites from the Zongyang area of the LYRB. Zircon LA-ICPMS U-Pb dating indicates the granites were emplaced at ca. 127 Ma. They have geochemical characteristics similar to those of A-type granites, with high total-alkali (10.5–10.7 wt.%), HFSEs (Zr + Nb + Ce + Y = 890–1011 ppm), high Ga/Al ratios (10,000 × Ga/Al = 3.19–3.25), and high whole-rock zircon saturation temperatures (850°C–900°C). In discrimination diagrams, samples plot in the A1-type granite field but close to the A1–A2 boundary. A representative whole-rock sample yielded an ISr ratio of 0.7066 and an εNd(t) value of – 5.3, with zircon εHf(t) and δ18O values of – 0.2 to – 4.3 and 5.95‰–6.79‰, respectively, all higher than those of depleted mantle, indicating the enriched nature of source materials. Apatites in the granite display mantle-origin characteristics. Incompatible element ratios (Y/Nb, Y/Ta, Nb/U and Ce/Pb) also support the enriched mantle source, and suggest that the source had experienced metasomatism, or the existence of crustal input during magmatic processes. Significant depletions in Ba, Sr, P, Ti, and Eu in the granites indicate fractional crystallization of feldspar and some accessory minerals. We conclude that the Zongyang granite were formed through fractional crystallization of oceanic island basalt (OIB)-like basic magmas derived from the lithospheric mantle. They are classified as A1 but their borderline A2 nature is most likely due to metasomatism by slab-derived fluids or melts, possibly involving crustal materials. Our results, together with those of previous studies, indicate that LYRB A-type granites, are the products of partial melting of the mantle or lower continental crust in an extensional setting, caused by slab rollback during the subduction of the Paleo-Pacific Plate.

A simple method was developed for achieving Fe separation and involved the use of a single column packed with AGMP-50 cation-exchange resin.

Matrix effects and mass bias of inorganic acids on boron isotope measurement by MC-ICP-MS have been investigated.

Matrix effect in SIMS aragonite oxygen isotopic analysis.

Rapid determination of the original boron composition from altered basaltic glass by SIMS boron isotopic profile analysis from the core to rim.

Six phengites from a restrict area in the Yuka terrane of the north Qaidam high/ultrahigh pressure (HP/UHP) metamorphic belt were dated using the 40Ar/39Ar method by laser stepwise heating, in order to investigate their geochronological significances and decipher the genesis of extraneous 40Ar in phengite. New 40Ar/39Ar age results show that the extraneous 40Ar exists in UHP metamorphic rocks (eclogite and amphibolite) phengite but not in their country rocks (gneiss and schist) phengite. High-Si and Mg-rich phengites from eclogite and phengite-bearing amphibolite yield disturbed age spectra, anomalously old apparent ages and a large variation in total gas ages (708-534 Ma) and isochron ages (681-513 Ma), indicating the existence of heterogeneous extraneous 40Ar. In contrast, relative low-Si and Fe-rich phengites from granitic gneiss and schist yield flat age spectra and geologically significant plateau ages (454.4 Ma and 418.0 Ma). The data points constituting the age plateaux yield isochrons with concordantly intercept ages of 456.2±2.3 and 418.1±2.2 Ma, corresponding to initial 40Ar/36Ar ratios of 177.3±151.2 and 287.1±16.9, respectively, implying that there is no extraneous 40Ar inside the minerals. The plateau age of 454.4 Ma recorded by phengite from granitic gneiss is interpreted as the age of cooling through its retention temperature for argon (ca. 400°C), and responding to the time of the Yuka metamorphic rocks exhumed from upper-mantle depth to middle-lower crustal levels (ca. 10 km in depth) after deep subduction. In contrast, the plateau age of 418 Ma from the schist should correspond to a Later Silurian ductile shearing deformation event. Considering the protoliths characteristics of the eclogite and amphibolite, the extremely high p-T metamorphic condition and aqueous fluid shortage environment during eclogite formation, we would suggest that the extraneous 40Ar*(not produced by in situ radiogenic decay of 40K) in phengites from Yuka is a locally derived component from the protolith rather than from a late infiltrating fluid.

The water flux delivered into the forearc mantle of currently active subduction zones remains poorly constrained. Estimates, which mostly derive from numerical modelling, have so far been untested, as shallow subduction processes are hindered by the serpentinised forearc mantle. Here, I examine the composition of near trench magmas from the southern Mariana and Matthew-Hunter rifts, which provides unique glimpses into slab dehydration underneath the forearcs of two modern subduction zones. The near trench magmas captured the water-rich slab fluids that usually serpentinise the cold forearc mantle. The near trench magmas possess higher markers in slab dehydration (Rb/Th = 3-141, Cs/Th = 0.04-17.79, H 2 O/Ce = 436-23,531) than do arc and back-arc magmas, implying that the subducted plates might dehydrate efficiently within 80 km from the trench.

In this study, we developed two new SIMS (secondary ion mass spectrometry) analytical protocols to simultaneously measure oxygen–hydrogen (O–H) isotopic compositions and water content for hydrous geological samples.

In ⁴⁰Ar/³⁹Ar dating, ³⁹Ar_K generated is dependent on irradiation conditions, and the accumulation fast neutron fluence is a critical parameter for ⁴⁰Ar/³⁹Ar dating.

Galvanic distortion resulting from near-surface heterogeneity has long been considered a major impediment to the accurate interpretation of magnetotelluric data. As this galvanic distortion effect is approximated by a real tensor, it can be solved numerically in the three-dimensional magnetotelluric inversion. To achieve this goal in a practical way, we have implemented the inverse solution of both the galvanic distortion and resistivity parameters in the widely used software package ModEM. To address the gradient domination problem of the distortion parameter over resistivity, a scaling scheme is proposed to balance their separate roles in the total gradient. Two synthetic datasets of the Block2-3D and the Oblique Conductor models provided in ModEM package were distorted and then used to validate the new implementation. Synthetic inversions demonstrate that the artifacts introduced by fitting the galvanic distortion effect can be removed and the regional structure is better resolved. A field data inversion test was conducted on the magnetotelluric data from the Red River Fault zone and its adjacent areas on the southern margin of the Tibetan Plateau. Using the distortion-free phase tensor, we show that the new inversion significantly removes the galvanic distortion artifacts from the shallower structure. It obtained a slightly different crustal structure and a clearer delineation of the upper mantle structure compared to the previous study.

This study reports an improved procedure for the simultaneous determination of Re–Os and S isotopic compositions of sulfur-bearing minerals using negative thermal ionization mass spectrometry (N-TIMS) and multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), respectively.