The improvement of saline soil is an important issue that cannot be ignored in the farmland soil environment. The change in soil salinity will inevitably affect the soil bacterial community. This ...experiment was based on moderately saline soil in the Hetao Irrigation Area, conducted by applying phosphogypsum (LSG), interplanting
with
(JP) and applying phosphogypsum and interplanting
with
(LSG+JP),and the local unimproved soil of a
orchard was used as the control (CK), to explore the effects of different improvement methods on soil moisture, salinity, nutrients, and bacterial community structure diversity during the growth period of
. The results showed that compared with that under CK, the LSG+JP treatment significantly decreased the soil EC value and pH value from the flowering stage to the deciduous stage (
<0.05), with an average decrease of 39.96% and 7.25%, respectively; the LSG+JP treatment significantly increased soil organic matter (OM) and available phosphorus (AP) content during the whole growth peri
Abstract
The Olkhon Terrane is thought to preserve a record of the initial collision of the Siberian Craton with its peripheral orogenic system during the early Paleozoic. However, the related ...tectono‐metamorphic process and its time‐scale remain obscure. To address this issue, new structural observations combined with U‐Pb zircon and monazite and
40
Ar/
39
Ar biotite geochronology were conducted in the migmatitic‐granitic Anga‐Sakhurta Zone of the terrane. An earliest syn‐collisional event associated with the development of a c. 500–480 Ma sub‐horizontal migmatitic fabric is confirmed. This early fabric was affected by later extensional doming in association with emplacement of partial melts (in terms of c. 470–445 Ma granite sills) parallel to the sub‐horizontal mechanical anisotropy. Subsequent upright folding leading to amplification of extensional domal structures and heterogeneous vertical transposition of composite horizontal fabric occurred soon after the doming, as indicated by intrusions of residual melts into the axial planes of the upright folds. The latest episode of deformation was marked by development of greenschist‐facies sinistral shear zones surrounding the Anga‐Sakhurta Zone at c. 420–400 Ma. An updated tectonic model involving (a) Middle–Late Ordovician crustal thinning associated with horizontal crustal flow, (b) Silurian crustal shortening related to northwards movement of Cambrian magmatic arc of the Birkhin Complex to the south, and (c) Early Devonian lateral extrusion and sinistral shearing associated with progression of the Birkhin Complex promontory, is proposed. Results from this study shed lights on the collisional evolution of peri‐Siberian orogenic system during the early stage evolution of the Central Asian Orogenic Belt.
Key Points
The Olkhon Terrane underwent Cambrian–Silurian shortening‐extension cycles and Devonian lateral extrusion and shearing
Cambrian to Devonian tectonic switches in the Olkhon Terrane mark the collisional evolution of peri‐Siberian orogenic system
Geodynamic evolution of the Olkhon Terrane closely matches to that of central segment of the Mongolian Collage
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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. Here we have described a suite of newly developed reference materials for SIMS zircon water content analysis and a modified micro-analytical technique (using a CAMECA IMS 1280-HR SIMS) that can simultaneously measure the zircon water content and oxygen isotopes. A total of 20 natural zircon grains/sherds were analyzed
via
Fourier transform infrared spectroscopy (FTIR), among which 8 (with good water content result reproducibility) were further analyzed by SIMS. Before the SIMS analysis, FTIR analyzed sample blocks were mounted with a Sn-based alloy to minimize degassing and background water. As in routine SIMS oxygen isotope measurement,
16
O
−
and
18
O
−
were collected using two Faraday cups, and in addition
16
O
1
H
−
was simultaneously measured using an electron multiplier. The measured
16
O
1
H/
6
O ratio was converted into water content, using a calibration line established based on SIMS
16
O
1
H
−
/
16
O
−
ratios
vs.
the FTIR water content. Both the internal and external precisions of corrected δ
18
O are <0.4 permil (2SE or 2SD). The internal precision of
16
O
1
H
−
/
16
O
−
ratios follows a Poisson error theoretical trend and is generally better than 0.3%. The external precision (reproducibility) of
16
O
1
H
−
/
16
O
−
ratios is better than 5% (2SD) for homogenous samples, and uncertainty of the calibrated water content is ∼10%.
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.
Water is essential for the formation of granites, but its origin and role in granite generation (i.e., dehydration vs. water‐fluxed melting) remain uncertain. These issues are addressed by combining ...water abundances and other geochemical indices in zircons from Late Mesozoic granites generated during the destruction of the North China Craton (NCC). The water contents in zircons from the NCC Early Cretaceous granites (763 ppm, median) are much higher than those of the NCC Jurassic granites (424–513 ppm), upper mantle and continental arc magmas (92–477 ppm). More importantly, the higher water contents in the voluminous Early Cretaceous granites also have higher zircon saturation temperatures, εHf(t), and lower δ18O values. These observations suggest a predominantly mantle origin for the water, and water‐fluxed crustal melting, in which larger water ingression produced more voluminous melts. The high‐water flux was likely related to the subduction of the Paleo‐Pacific Plate, which ultimately destabilized the NCC.
Plain Language Summary
The fact that water is essential in generating granites has been known for a long time. However, its detailed role is poorly understood due to heterogeneous source and complex melting reactions involved in the generation of granites. As a fundamental issue of granite genesis, it remains a long‐standing problem to distinguish the two major mechanisms, that is, hydrous‐mineral‐dehydration melting versus external‐water‐added melting. In this study, the water content of zircon combined with other lines of clues of I‐type granites that generated during the destruction of North China Craton (NCC) in Late Mesozoic collectively points to water‐added crustal melting rather than dehydration melting. The isotope composition of zircon suggests a mantle provenance of water. The highest water contents occurred in the Early Cretaceous granites, corresponding to the climax of the NCC destruction. Higher zircon water contents in Early Cretaceous granites indicate higher water‐flux into thelithospheric mantle and overlying crust by the subduction of the paleo‐Pacific plate. Accordingly, water played a significant role in cratonic destruction.
Key Points
Water contents of zircons from North China Craton Jurassic granites are comparable with continental arc magmas
Higher zircon water contents are found in voluminous Early Cretaceous granites generated during the climax of cratonic destruction
Early Cretaceous granites were generated by water‐fluxed crustal melting, the water in which has a predominant mantle origin
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Secondary ion mass spectrometry (SIMS) has a wide range of applications in Earth Science research, thanks to its high precision and sensitivity, and its capacity in direct insitu micromeasurement. ...The technique is operated in ultra‐high vacuum (UHV) conditions, especially for the measurement of volatiles such as hydrogen, or the water content in nominally anhydrous minerals (NAMs). To minimize the water background and obtain accurate and precise water contents in NAMs (eg, olivine) critical parameters such as presputtering time, field aperture (FA), dynamic transfer on/off, and primary beam current intensity were investigated for a CAMECA IMS 1280‐HR system. When the chamber vacuum reaches approximately 2 × 10−9 mbar, we set the DTOS OFF, raster size to 50 μm and primary beam current to 5 nA, and used 2000 μm FA and 170‐second presputtering time. Consequently, an approximately 1.2 ppmw water background and 3.6 ppmw limit of detection (LOD) were yielded, from analyzing the San Carlos olivine. Meanwhile, the water content and homogeneity of a range of olivine minerals were characterized for potential use as reference materials for SIMS water content measurement. Olivine water content calibration curve was also established by comparing the Fourier transform infrared (FTIR) results with the SIMS‐measured 16O1H−/16O− ratios. Accuracy and precision of water content measurement were estimated to be better than approximately 10% in this study.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Large-geometry secondary ion mass spectrometry (LG-SIMS) is routinely used to determine the elemental and isotopic compositions, thanks to its high sensitivity and in situ micro-analysis capability. ...Its large volumes of transfer and coupling column, however, might bring low vacuum and high background of volatile elements (esp. H), which hampers its application in ultralow H2O content measurement. In this study, we report a modified analytical procedure to accurately analyze samples with ultralow-level H2O content by using a LG-SIMS of type CAMECA IMS 1280-HR. Based on four new water content working reference materials of quartz glasses with H2O contents ranging from ca. 0 to 39 ppm, the estimated detection limit of LG-SIMS is 0.15 ppm for H2O. This ultralow detection limit is achieved mainly by the intrinsic high sensitivity of the instrument and the conjunctive usage of a stabilized temperature-controlled cooling trap device and a novel tin–bismuth alloy mount preparation technology, which are able to maintain a vacuum pressure at 1.7 × 10−9 mbar in the analysis chamber. Based on these new improvements, our approach can potentially become a routine choice for analyses of H2O content and oxygen–hydrogen isotopes for (extra)terrestrial materials with ultralow-level water content.
Abstract
To explore the response of atrazine (AT) degradation rate, soil organic matter (SOM) distribution and the relationship between them to straw mulching and nitrogen application, field ...experiments were conducted to study the distribution of SOM content and AT degradation rate under different straw returning modes combined with nitrogen fertilization in 2 years in Hetao Irrigation District. No (N
0
), low (N
L
), medium (N
M
), and high (N
H
) levels of N fertilization were incorporated into the soil combined with the surface coverage straw (Treatment BN
0
, BN
L
, BN
M
, BN
H
, respectively) and the deeply buried straw (Treatment SN
0
, SN
L
, SN
M
, SN
H
, respectively). The traditional cultivation was used as a control treatment (Treatment CK). The results showed that SOM content of Treatment B was accumulated in 0~20 cm soil layer. The largest SOM content of Treatments B in 0~20 cm soil layer was found in BN
H
treatment, with an average increase of 14.2% and 24.1% significantly when compared with those in CK and SN
H
(
P
< 0.05), respectively. The SOM content of Treatments B increased with the increase of nitrogen application and decreased with the deepening of soil depth. The SOM content of Treatment S was accumulated in the soil layer (20~40 cm and 40~60 cm) near the inter-layer. With the increase of nitrogen application and depth of soil layer, the SOM content increased firstly and then decreased. SN
M
had the largest SOM content in the soil layer of 20~40 cm and 40~60 cm, with an average increase of 82.6% and 67.7% when compared with Treatment CK (
P
< 0.05). In the soil layer over 60 cm, there was no significant difference in SOM content of different straw returning methods under the same nitrogen level (
P
> 0.05). Straw returning methods and nitrogen application level significantly affected AT digestion rate and digestion half-life, with significant differences among treatments (
P
< 0.05). It found that treatment SN
M
had the highest digestion rate and the shortest half-life of AT. Compared with Treatment CK, the digestion rate of Treatment SN
M
was increased by 5.3% on average, and the half-life was shortened by 3.9 days on average. Single regression and stepwise regression analysis of the half-life of AT degradation and SOM content in different soil layers (0~20 cm and 20~40 cm) showed that the degradation of AT was greatly affected by SOM content of 20~40 cm soil layer. Based on the comprehensive analysis, the effect of straw deep burial combined with medium nitrogen application rate (Treatment SN
M
) was best, which could achieve the goal of increasing SOM content and shortening the half-life of AT digestion. The research provided a technical support for straw resource utilization, alleviated AT pollution and improved farmland ecological environment in Hetao Irrigated District.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Secondary ion mass spectrometry (SIMS) is a powerful technique for
in situ
measurement of trace amounts of water in nominally anhydrous minerals (NAMs). The structure and chemistry of the substrate ...are well known to have a significant effect on how easily elements are ionized when sputtered with a primary beam, resulting in different ion yields,
i.e.
, matrix effect. The matrix effect highlights the importance in choosing reference materials with a similar crystal structure and chemistry for calibration. However, these kinds of reference materials are generally scarce. In this study, we investigate four clinopyroxene (cpx) and five orthopyroxene (opx) newly developed reference materials for SIMS water content analysis. Nine samples were analyzed
via
a Fourier Transform Infrared Spectrometer (FTIR) and SIMS to determine their water content and investigate their homogeneity. Our results show that these samples are homogeneous in terms of water contents, indicated by the low standard deviation (<18.6%, 2sd) for both inter- and intra-fragments, except that Diopside-cpx shows some inter-fragment heterogeneity, which should be used with caution. The cpx and opx sample suites have water ranges of 24 ± 3 to 774 ± 26 μg g
−1
(2sd) and 45 ± 3 to 534 ± 59 μg g
−1
(2sd), respectively, extending the covered ranges of the existing reference materials and approaching most natural samples. Thus, these samples can be used as reference materials for SIMS pyroxene water content analysis.
In this study, we developed four clinopyroxene (cpx) and five orthopyroxene (opx) samples as reference materials for SIMS water content analysis.
To provide an appropriate tillage fertilization model for improving N utilization efficiency and increasing production, the field experiments were conducted to study the effects on root distributions ...and N utilization efficiency of summer maize involving different straw mulching modes combined with N fertilization. No (N0), low (N1), medium (N2), and high (N3) levels of N fertilization were incorporated into soil combined with the surface coverage straw (Treatment B) and the deeply buried straw (Treatment S). The traditional cultivation was used as control treatment. The results shown that treatments S had significantly promoted deep root growth, and the root length density (RLD) increased with increases in N application rate. SN2 and SN3 treatments' average RLD were significantly increased by 67.5% and 68.1% in the greater than 40 cm soil layers. While the Treatment B had significantly increased the RLD in 0 -30 cm soil layers only. With increases in N application rate, the effect on summer maize yields increase under Treatment B were not significantly, and only BN3 increased by 0.4%, while under Treatments S were found to first increase, and then decrease. The apparent recovery efficiency of applied N, N uptake and summer maize yield of SN2 had increased by 66.8%, 20.4%, and 9.3%. Therefore the rational tillage fertilization model was deeply buried straw combined with medium N fertilizer in Hetao Irrigation District.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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. These two protocols involve the measurement of two sets of secondary ion contents: (1)
1
H,
2
H,
16
O,
18
O; and (2)
16
O,
16
O
1
H,
18
O,
17
O
1
H,
16
O
2
H. Both measurements utilize a hybrid dynamic multi-collector system of CAMECA IMS 1280-HR, which benefits from both the static multi-collector mode and peak-hopping mono-collector mode. These new methods can simultaneously measure (with high-precision) the
18
O/
16
O ratio in static multi-collector mode without trading off its analytical precision, and
1
H/
16
O (or
16
O
1
H/
16
O) and
2
H/
1
H (or
16
O
2
H/
16
O
1
H) ratios in conventional peak-hopping mono-collector mode. Three glass samples (LBS7H, LBS5H and LBS6H-) with known water contents and two apatite samples (Kovdor, Durango) with known oxygen-hydrogen isotopes and water content were measured to verify the protocols' reliability. The olivine crystal San Carlos with ∼1 ppmw water content was used for background monitoring. For the apatite samples, the external precision (spot-to-spot reproducibility) for δ
18
O and δD is better than 0.56‰ (2SD) and 54‰ (2SD), respectively. After eliminating the outlier (beyond 3SD error), the external precision of
16
O
1
H/
16
O or
1
H/
16
O ratio improves to 10.27% (2SD). For the glass samples, the water content calibration curves, which were constructed by comparison of the known water content with the SIMS measured
16
O
1
H/
16
O or
1
H/
16
O ratios, yielded good correlations. It is noteworthy that the apatite and glass samples can have a uniform water content calibration curve for protocol 1, but not for protocol 2, indicating different matrix effects for the two protocols.
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.
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