Derelict fishing nets in Puget Sound and the Northwest Straits: Patterns and threats to marine fauna

Derelict fishing gear remains in the marine environment for years, entangling, and killing marine organisms worldwide. Since 2002, hundreds of derelict nets containing over 32,000 marine animals have been recovered from Washington’s inland waters. Analysis of 870 gillnets found many were derelict for years; most were recovered from northern Puget Sound and high-relief rocky habitats and were relatively small, of recent construction, in good condition, stretched open, and in relatively shallow water. Marine organisms documented in recovered gillnets included 31,278 invertebrates (76 species), 1036 fishes (22 species), 514 birds (16 species), and 23 mammals (4 species); 56% of invertebrates, 93% of fish, and 100% of birds and mammals were dead when recovered. For all taxa, mortality was generally associated with gillnet effectiveness (total area, age and condition, and suspension in the water). Mortality from derelict fishing gear is underestimated at recovery and may be important for species of economic and conservation concern.     

Perfluorinated compounds in the surface waters of Puget Sound,Washington and Clayoquot and Barkley Sounds,British Columbia

Perfluorinated compounds (PFCs) are persistent organic contaminants detected in various environmental matrices including sediment, air, biota, and water. The objectives of this study was to evaluate the occurrence of these contaminants within the surface waters of the Pacific Northwest region and through relative concentrations and ratios, to assess their possible sources. Surface waters were extracted and analyzed by liquid chromatography tandem mass spectrometry (LCMSMS). Perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were the most commonly detected PFCs. Total PFC concentrations detected ranged from 1.5 to 41 ng L-1. Surprisingly, levels of PFCs in the more urbanized Puget Sound waters were comparable to those measured from the more rural region of Clayoquot and Barkley Sounds in British Columbia. The ratio of PFHpA/PFOA were also similar between the two regions, suggesting that the burden of PFCs throughout the region results from direct input from regional sources.     

Differential presence of anthropogenic compounds dissolved in the marine waters of Puget Sound, WA and Barkley Sound, BC

Organic compounds were evaluated in March 2010 at 22 stations in Barkley Sound, Vancouver Island Canada and at 66 locations in Puget Sound. Of 37 compounds, 15 were xenobiotics, 8 were determined to have an anthropogenic imprint over natural sources, and 13 were presumed to be of natural or mixed origin. The three most frequently detected compounds were salicyclic acid, vanillin and thymol. The three most abundant compounds were diethylhexyl phthalate (DEHP), ethyl vanillin and benzaldehyde (∼600 ng L⁻¹ on average). Concentrations of xenobiotics were 10-100 times higher in Puget Sound relative to Barkley Sound. Three compound couplets are used to illustrate the influence of human activity on marine waters; vanillin and ethyl vanillin, salicylic acid and acetylsalicylic acid, and cinnamaldehyde and cinnamic acid. Ratios indicate that anthropogenic activities are the predominant source of these chemicals in Puget Sound.     

D/H and O/O ratios of water in the crater lake at Kusatsu-Shirane volcano, Japan

The D/H and ¹⁸O/¹⁶O ratios of water in the active crater lake situated on the Kusatsu-Shirane volcano, Japan are about 20 and 6‰, respectively, higher than local meteoric water. The ratios show seasonal variations superimposed on a gradual change over nine years. The isotopic ratios started to increase in early 1990 and decrease in the spring of 1995. The seasonal variation which is high in winter and low in summer correlates with the temperature difference between lake water and ambient air. The large temperature difference in winter enhances the evaporation of lake water and produces the enriched isotopic ratios relative to the ratios in summer. The accumulation of snow and the decrease in the flux of meteoric water into the lake strengthens the winter-time isotopic enrichment. The enriched isotopic ratios of the lake water over a long time result from the addition of an end member with heavy isotopic ratios contained in a thermal fluid supplied to the lake. Considering the water balance in the lake, the isotopic ratios of the thermal fluid were found to be close to the lake water itself, suggesting the circulation of the lake water seeping through lake floor. Based on the correlation between Cl⁻concentration and the isotopic ratios, the contribution by the heavy end member was estimated to be 25–36% relative to the enrichment by evaporation. The heavy end member could be a liquid phase evolved from a parental fluid, which is a mixture of local meteoric water and a magmatic fluid as found in high-temperature volcanic gases.     

三峡库区澎溪河典型优势藻细胞N/P比与限制性评价的原位分析

本文通过选取水华鱼腥藻(Anabaena flos-aquae)、铜绿微囊藻(Microcystis aeruginosa)、空球藻(Eudorina sp.)和湖北小环藻(Cyclotella hubeiana)为三峡库区流域中典型的优势藻,在澎溪河进行原位培养试验,跟踪监测了三峡水库不同运行时期4种典型优势藻细胞氮(Cell-N)、磷(Cell-P)浓度以及环境水体中的总氮(TN)、总磷(TP)浓度,并且结合团队之前的研究成果,根据临界(供应)N/P摩尔比、细胞N/P摩尔比和Guildford的TN/TP摩尔比评价标准对库区水体的营养限制状态进行了评价,为进一步揭示三峡水库运行下支流水域富营养化过程与生理特征的限制性评价提供研究基础.原位试验结果表明:3个评价标准下水体的营养(氮或磷)限制状态基本相同,低水位时期水体无机磷营养盐比较贫乏,在试验初期没有显著的营养盐限制而在末期受到了磷的相对限制;高水位试验初期和末期均未呈现显著的营养盐限制;泄水期营养盐变动频繁,试验初期表现为氮限制而末期表现为磷限制.虽然各藻种在不同时期会表现出不同的营养盐限制性,但总的来看,临界N/P比和细胞N/P比的阈值范围具有一定指示作用,能够从藻类细胞生理的角度对水体的营养状况作出初步评价.     

Composition, Abundance and Stratification of Macrobenthos in the Marine Area Impacted by Tar Aggregates Derived from the Haven Oil Spill (Ligurian Sea, Italy)

The impact of tar aggregates deriving from the Haven oil spill that occurred in 1991 on the soft-bottom macrobenthos off Arenzano (Ligurian Sea, NW Mediterranean; Italy) was investigated in this study. Core samples were collected to evaluate the composition, abundance and stratification of macrobenthos in three contaminated and three control sites. The distribution of tar aggregates (often settled by hydroids, bryozoans and serpulids) in the impacted area did not show distinct patterns related to sediment depth. The macrobenthos was numerically dominated by polychaetes, followed by crustaceans (amphipods, isopods and tanaids) and sipunculids, whereas bivalve molluscs were less represented. Ophiuroids and nemerteans were only occasionally found. Stratification was the main factor explaining the distribution of benthic invertebrates, highest abundances being observed in the upper 5 cm of sediment, while densities of individuals declined sharply in deeper sediment layers. No significant differences were observed in the abundance of both the whole benthic assemblage and of the main benthic taxonomic groups between contaminated and control sites. The higher abundance of sipunculids at the contaminated sites, instead, was attributed to the availability of empty tubes of polychaetes in which they take refuge. The polychaetes/amphipods ratios did not show strong differences between impacted and control sites. Multivariate analysis (MDS) showed a wide scattering among deep bottom samples and a comparatively high similarity among intermediate and superficial layers, regardless of the contamination level. In conclusion, the results reported here suggest that tar aggregates do not determine appreciable detrimental effects on the soft-bottom macrobenthos, which appeared to have recovered towards natural pristine conditions.     

(40)~Ar/(39)~Ar chronology and geochemistry of high-K volcanic rocks in the Mangkang basin, Tibet

Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5±0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5±0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. et al., implying that they were formed in the same tectonic setting.     

青海玛多MS7.4地震前LURR与OLR短临异常关联性研究

加卸载响应比(LURR)是根据岩石应力-应变关系的动态演化规律提出的地震预测方法。以Benioff应变为响应量,分析青海玛多M_S7.4地震前震中及其周边400 km内的LURR异常的演化特征发现,在震前一个月LURR值达到最高值,半个月之后出现高值回落的现象,说明此时孕震区岩石介质已进入屈服阶段的末端。在此基础上,利用NOAA卫星地面长波辐射(OLR)数据,分析高值回落后(5月14—25日)地面长波辐射值的短临异常演化规律。结果显示:震前在空间上仅仅在震中北部出现OLR显著且连续的短临异常变化并呈现向震中扩展的趋势,在时间上整个演化过程经历了初始增温-异常扩展-达到峰值-异常减弱-地震发生-异常消失等6个阶段。LURR和OLR震前短临异常特征说明,回落前的LURR高值反映了岩石介质屈服阶段的结束,OLR在一定程度上可以表征处于临界状态的活动断层的构造应力累积状态,综合研究两种物理参量震前异常演化特征,有助于更准确评估地震活动趋势。     

青藏高原湖泊Mg~(2+)、Ca~(2+)和Mg/Ca盐度指示意义的初步分析

总结了青藏高原地区400多个湖泊湖水的Mg2+、Ca2+和Mg/Ca等水化指标与湖水盐度的相关关系,以及这种关系随着湖水变化(不同采样时间和采样点以及自然蒸发)而产生的变化规律.结果表明:青藏高原湖泊湖水的Mg2+浓度与盐度具有较为稳定的正相关关系,而Ca2+和Mg/Ca与盐度的相关性较弱.在对于某一特定水化学类型的湖泊,一般碳酸盐型湖泊的Mg2+、Ca2+以及Mg/Ca等指标与盐度均没有明显的相关性;硫酸盐型湖泊中Mg2+浓度和盐度呈现较高的正相关关系,而Ca2+以及Mg/Ca与盐度的相关性仍很弱;而在氯化物型湖泊中,Mg2+浓度与盐度呈更高的正相关性,Ca2+浓度也与盐度呈一定的正相关性,Mg/Ca这一指标与盐度的相关性依然很弱.而对某一特定湖泊,在不同演化阶段或不同的采样地点,Mg2+浓度与盐度仍然保持明显的正相关关系,而Ca2+以及Mg/Ca与盐度的相关性仍然不稳定或很弱.在青藏高原作古环境重建应用的时候,湖水Mg2+浓度是古盐度一个较好的转换指标,而Ca2+以及Mg/Ca的古盐度指示意义相对较弱.     

A study of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in the livestock waste compost of Hong Kong, PR China

Composting is one of the waste disposal methods adopted for disposal of livestock waste in Hong Kong. The composting livestock waste normally undergoes 6–8 weeks fermentation, followed by 16–20 weeks maturation. The matured compost is sold as soil conditioner in the local market. In 2006, feedstock material and a time-series of compost samples were collected throughout the fermentation and maturation process from the Sha Ling Composting Plant in the New Territories. The feedstock material and compost samples were analyzed for contents of three unintentional persistent organic pollutants (POPs), i.e. dioxins/furans, dioxin-like PCBs and total PCBs. These POPs are unintentionally produced by-products of chemical industrial processes and combustion processes. Selected heavy metals were also analyzed, which served as conservative tracers to determine potential mass loss during the composting process. Levels of contamination by these POPs were found to be low in the matured compost for sale. The mean concentrations (lower–upper bound) of total dioxins/furans, total dioxin-like PCBs and total PCBs were 2.01–2.05 ng I-TEQ/kg dw, 0.04–0.05 ng WHO-TEQ/kg dw and 1.55–1.55 μg/kg dw, respectively. Progressively elevated levels of these POPs were observed in the compost samples during the fermentation process. Analysis of the congener profiles revealed that the heptaCDD and octaCDD were the main contributors to the observed increase in dioxin/furan content. The possible sources of dioxins/furans in the compost were discussed. The study results established a local dioxins/furans emission factor specific to the trade and provided a better estimate of the annual dioxins/furans emission for the livestock waste composting activity in Hong Kong.     

PCB, PCDD/F and PBDE levels and profiles in crustaceans from the coastal waters of Brittany and Normandy (France)

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analysed in the muscle of various edible marine crustaceans (spider crab, edible crab, velvet swimming crab and Norway lobster) from the Brittany and Normandy coasts (France). The highest concentrations were measured in species collected from Antifer (Seine Bay). PCB and PBDE patterns in crustacean muscles were similar and independent of the geographical area with the predominance of the high chlorinated PCBs (CB153, 138, 118 and 180), and of a few PBDE congeners (BDE47, BDE99, BDE100 and BDE28). Oppositely, dioxin contamination differed with site. The major component in crustaceans from the Seine Bay was 2378-TCDF, whereas specimens from cleaner areas had higher relative concentrations of OCDD. Finally, the comparison of the spider crab contaminant profiles to those measured in mussel and sea bass highlighted two different trends: decapod crustaceans possess relatively strong capacity to metabolise PCBs and PBDEs; however these species might be used as bioindicators for dioxin pollution monitoring in the marine coastal environment.     

A review and assessment of tributyltin contamination in the North Sea,based on surveys of butyltin tissue burdens and imposex/intersex in four species of neogastropods

It is evident from measures of butyltin tissue burdens and imposex or intersex in neogastropods that tributyltin (TBT) contamination of coastal waters and open parts of the North Sea is now low. It has been declining for at least the past decade. This is probably due to two measures. First, regulations prohibiting the use of TBT-based paints on small boats and fish farms have reduced inputs of TBT from these sources so that they are now negligible (except possibly where the regulations are flaunted). Second, there is evidence from sites, where commercial vessels are the sole source of TBT, that the adoption of TBT SPC paints has been effective in reducing environmental levels of these contaminants. However, poor dockyard practices, allowing TBT-contaminated wastes, including paint flakes, to accumulate in sediments have left a legacy of hot-spots of contamination in some ports. The impact is localised so that TBT contamination is low in coastal areas immediately adjacent to ports.     

An assessment of the geomorphodiversity and land use/cover change (LUCC) effects associated with landslides in Meghalaya,India

The Shillong Plateau in the Eastern Himalayas is exposed to high seismicity, neo-tectonic activity and orographic precipitation that aggravated landslides in the region by affecting hillslope processes. Landscape development is influenced by landslide phenomenon and depends upon geomorphic processes and geomorphodiversity (GmD). It is linked intimately with geomorphology, hydrology and soil type. This study uses a remote sensing and GIS-based approach to assess the spatial linkage between GmD and landslide distribution in Meghalaya (India). GmD index (GmDI) is developed using geological, morphometric and geomorphological parameters and analysed with landslide distribution. The landslide distribution considering land use/cover change (LUCC) is also examined. The result shows that the region with high-relief, valley and depression zone, mainly along the Dauki fault, have a high to a very high GmDI. About 61% of landslide localities are in zones of high GmDI, concentrated in the central and eastern parts of Meghalaya. Density analysis of the very high class (class 5) of GmD confirms the same. Most of these landslides occur in dense and light-vegetated landmasses. However, the LUCC analysis reveals a significant increase in the built area on steeper slopes (average expansion ratio of 2.30 for slopes >15°) between 2017 and 2022, indicating a rising threat of landslides in urban areas of Meghalaya. The study presents the importance of GmD in active tectonic regions with particular reference to landslide potential and recent LUCC. It can aid decision-makers in planning sustainable developments and risk mitigation strategies for landslide hazards and geoconservation.     

Soil characterization in urban areas of the Bajo Segura Basin (Southeast Spain) using H/V, F-K and ESAC methods

Bajo Segura Basin, placed in the south of Alicante province (southeast Spain), is a region of moderate seismicity, which presents frequent seismic episodes. This region, as the rest of south-eastern part of Spain, is growing both economically and demographically. Hence, the presence of soft soils in a seismic region where many towns and villages are placed shows the importance of an adequate characterization of the site effects study in this area.The present work investigates the use of noise measurements for soil characterization by the application of H/V method and array techniques: extended spatial autocorrelation (ESAC) and frequency-wave number (F-K) in three urban areas of the Bajo Segura Basin. The application of these methods will help us to estimate the resonance frequencies, as well as shear-wave velocity profiles, having a better understanding of the sediment depth and site effects phenomena at the studied places.The estimated velocity profiles are used to model the fundamental mode Rayleigh wave ellipticity curves and the S-wave site transfer functions. Finally, the correlation between this curves and the experimental H/V analysis has allowed us a better assessment of the site response in the studied areas.     

Photochemical Degradation of Hydrophilic Xenobiotics in the UV/H2O2-process. Influence of Bicarbonate on the Degradation Rate of EDTA, 2-Amino-1-naphthalenesulfonate,Diphenyl-4-sulfonate,and 4,4′-Diaminostilbene-2,2′-disulfonate

Hydrophilic xenobiotics can be eliminated in the UV/H₂O₂-process. The oxidation in this process is enhanced by the photolytically generated HO radicals. Bicarbonate is able to scavenge HO radicals. So it was expected that the degradation rates of the investigated xenobiotics were affected by the influence of bicarbonate. In contrast to the widely described decrease of the degradation rate, a much more complex situation was found in this investigation. The degradation rates of 2-amino-1-naphthalenesulfonate and diphenyl-4-sulfonate were decreased and reached for high concentrations of bicarbonate the values of the photolytical degradation rate. The degradation of 4,4′-diaminostilbene-2,2′-disulfonate was accelerated significantly in the presence of bicarbonate. The degradation rate of EDTA was increased at small concentrations of bicarbonate and decreased at higher concentrations.     

Alpine tectonic evolution of a Jurassic subduction-accretionary complex: Deformation,kinematics and Ar/Ar age constraints on the Mesozoic low-grade schists of the Circum-Rhodope Belt in the eastern Rhodope-Thrace region,Bulgaria-Greece

Deformation of the Circum-Rhodope Belt Mesozoic (Middle Triassic to earliest Lower Cretaceous) low-grade schists underneath an arc-related ophiolitic magmatic suite and associated sedimentary successions in the eastern Rhodope-Thrace region occurred as a two-episode tectonic process: (i) Late Jurassic deformation of arc to margin units resulting from the eastern Rhodope-Evros arc–Rhodope terrane continental margin collision and accretion to that margin, and (ii) Middle Eocene deformation related to the Tertiary crustal extension and final collision resulting in the closure of the Vardar ocean south of the Rhodope terrane. The first deformational event D₁ is expressed by Late Jurassic NW-N vergent fold generations and the main and subsidiary planar-linear structures. Although overprinting, these structural elements depict uniform bulk north-directed thrust kinematics and are geometrically compatible with the increments of progressive deformation that develops in same greenschist-facies metamorphic grade. It followed the Early-Middle Jurassic magmatic evolution of the eastern Rhodope-Evros arc established on the upper plate of the southward subducting Maliac-Meliata oceanic lithosphere that established the Vardar Ocean in a supra-subduction back-arc setting. This first event resulted in the thrust-related tectonic emplacement of the Mesozoic schists in a supra-crustal level onto the Rhodope continental margin. This Late Jurassic-Early Cretaceous tectonic event related to N-vergent Balkan orogeny is well-constrained by geochronological data and traced at a regional-scale within distinct units of the Carpatho-Balkan Belt. Following subduction reversal towards the north whereby the Vardar Ocean was subducted beneath the Rhodope margin by latest Cretaceous times, the low-grade schists aquired a new position in the upper plate, and hence, the Mesozoic schists are lacking the Cretaceous S-directed tectono-metamorphic episode whose effects are widespread in the underlying high-grade basement. The subduction of the remnant Vardar Ocean located behind the colliding arc since the middle Cretaceous was responsible for its ultimate closure, Early Tertiary collision with the Pelagonian block and extension in the region caused the extensional collapse related to the second deformational event D₂. This extensional episode was experienced passively by the Mesozoic schists located in the hanging wall of the extensional detachments in Eocene times. It resulted in NE-SW oriented open folds representing corrugation antiforms of the extensional detachment surfaces, brittle faulting and burial history beneath thick Eocene sediments as indicated by 42.1–39.7 Ma ⁴⁰Ar/³⁹Ar mica plateau ages obtained in the study. The results provide structural constraints for the involvement components of Jurassic paleo-subduction zone in a Late Jurassic arc-continental margin collisional history that contributed to accretion-related crustal growth of the Rhodope terrane.     

Late Carboniferous – Middle Permian arc/forearc‐related basin in Central Asian Orogenic Belt: Insights from the petrology and geochemistry of the Shuangjing Schist in Inner Mongolia,China

The Solonker Suture Zone is thought to record the terminal evolution of the Central Asian Orogenic Belt (CAOB) in Inner Mongolia. However, two contrasting interpretations of the timing of suturing of the Solonker Suture Zone exist: (i) Permian to Early Triassic; and (ii) Middle Devonian or Late Devonian to Carboniferous. The Shuangjing Schist is exposed in the Linxi area along the Xar Moron Fault Zone, which marks the southern boundary of the Solonker Suture Zone in the eastern section of the CAOB, and thus provides insight into the timing of suturing of the Solonker Suture Zone. Detailed and systematic analysis of the petrology and geochemistry of the Shuangjing Schist shows that the Shuangjing Schist developed by greenschist facies prograde metamorphism of a volcanisedimentary rock series protolith. The volcanic parts of the Shuangjing Schist are a calc‐alkaline series with large volumes of intermediate members and subordinate acidic members. Volcanism occurred in a magmatic arc on the continental margin and was induced by subduction‐related magmatism resulting from mantle metasomatism. The sedimentary parts of the Shuangjing Schist reflect a transition from continental shelf to abyssal plain sedimentation. The formation of the Shuangjing Schist is suggested to be related to closure of an arc/forearc‐related ocean basin. The timing is constrained by a laser ablation inductively coupled plasma–mass spectrometry (LA‐ICP–MS) U–Pb magmatic zircon age of 298 ± 2 Ma from a carbonaceous biotite–plagioclase schist that was intruded by granite at 272 ± 2 Ma. In the Linxi area, southward subduction of the arc/forearc basin led to uplift, thickening, collapse, and erosion of the overriding continental crust. Collapse induced extension and widespread magmatism along the volcanic arc at the northern margin of the North China Craton. The closure of the arc/forearc‐related oceanic basin led to the formation of Late Permian to Middle Triassic collisional granites and the subsequent end of the collision of the Solonker Suture Zone.     

Paleomagnetism,magnetic fabric,and <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar dating of Pliocene and Quaternary ignimbrites in the Arequipa area,southern Peru

⁴⁰Ar/³⁹Ar ages and paleomagnetic correlations using characteristic remanent magnetizations (ChRM) show that two main ignimbrite sheets were deposited at 4.86 ± 0.07 Ma (La Joya Ignimbrite: LJI) and at 1.63 ± 0.07 Ma (Arequipa Airport Ignimbrite: AAI) in the Arequipa area, southern Peru. The AAI is a 20–100 m-thick ignimbrite that fills in the Arequipa depression to the west of the city of Arequipa. The AAI is made up of two cooling units: an underlying white unit and an overlying weakly consolidated pink unit. Radiometric data provide the same age for the two units. As both units record exactly the same well-defined paleomagnetic direction (16 sites in the white unit of AAI: Dec = 173.7; Inc = 31.2; α95 = 0.7; k = 2749; and 10 sites in the pink unit of AAI; Dec = 173.6; Inc = 30.3; α95 = 1.2; k = 1634), showing no evidence of secular variation, the time gap between emplacement of the two units is unlikely to exceed a few years. The >50 m thick well-consolidated white underlying unit of the Arequipa airport ignimbrite provides a very specific magnetic zonation with low magnetic susceptibilities, high coercivities and unblocking temperatures of NRM above 580°C indicating a Ti-poor titanohematite signature. The Anisotropy of Magnetic Susceptibility (AMS) is strongly enhanced in this layer with anisotropy values up to 1.25. The fabric delineated by AMS was not recognized neither in the field nor in thin sections, because most of the AAI consists in a massive and isotrope deposit with no visible textural fabric. Pumices deformation due to welding is only observed at the base of the thickest sections. AMS within the AAI ignimbrite show a very well defined pattern of apparent imbrications correlated to the paleotopography, with planes of foliation and lineation dipping often at more than 20° toward the expected vent, buried beneath the Nevado Chachani volcanic complex. In contrast with the relatively small extent of the thick AAI, the La Joya ignimbrite covers large areas from the Altipano down the Piedmont. Ti-poor titanomagnetites are the dominant magnetic carriers and AMS values are generally lower than 1.05. Magnetic foliations are sub horizontal and lineations directions are scattered in the LJI. The AMS fabrics are probably controlled by post-depositional compaction and welding of the deposit rather than transport dynamics. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar chronology and geochemistry of high-K volcanic rocks in the Mangkang basin,Tibet

Our two newly obtained high-quality ⁴⁰Ar/³⁹Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ± 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ± 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. et al., implying that they were formed in the same tectonic setting.