Cenozoic volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, China： Petrochemical evidence for partial melting of the mantle-crust transition zone

Neogene volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, are represented by a typical intermediate-basic and intermediate alkaline rock association, with latite-trachyte as the main rock type. The results of chemical analysis are: SiO2=52%–62%, Al2O3>15%, Na2O/K2O>1 and MgO<3.30%. In addition, the volcanic rocks are LREE-enriched with LREE/HREE=10–13, (La/Yb)N=15–19, and show a weak negative Eu anomaly with δEu=0.71–0.89. The close relationship between Mg# and SiO2 and the co-variation of the magmatophile elements and ultra-magmatophile elements such as La/Sm-La and Cr-Tb indicate that this association of volcanic rocks is the product of comagmatic fractional crystallization. The rock association type and lower Sm/Yb values (Sm/Yb=3.23–3.97) imply that this association of volcanic rocks should have originated from partial melting of spinel lherzolite in the lithospheric mantle. On the other hand, the weak negative Eu anomaly and relative depletion in Nb, Ta and Ti reflect the features of terrigenous magma. So the Neogene Belog Co alkaline volcanic rocks should be the result of partial melting of the special crust-mantle transition zone on the Qinghai-Tibet Plateau.     

Organic Material and Trace Elements of Bituminous Rocks in the Ozankiiy Field, Ankara, Turkey

Bituminous rocks in the Ozankoey （Ankara） field are different from those of the Paleocene- Eocene Mengen and Giineytepe （Bolu） regions in metal enrichment levels. Organic carbon （Corg） content of organic material-rich rocks in the Ozankoey （Ankara） field is 3.66-40.72% wt averaging 14.34%. The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material （The dominant kerogen type is Type-I with a limited amount of Type-Ⅱ kerogen.）. The bituminous rocks in the Ozankoey field are enriched in heavy metals such as Ni, Mn, As and Cr. In comparison with the average enrichment values of dements, Ni, Mn, As and Cr in bituminous shales of the Ozankoey field are as about 4.38, 14.93, 10.90 and 5.58 times as average values. The average concentrations of these heavy metals are also as high as 215× 10^-6, 828 × 10^-6, 58.54 × 10^-6, and 148 × 10^-6 respectively. In addition, sorption properties of day and organic materials are also important for metal enrichments in the bituminous shales.     

Organic Material and Trace Elements of Bituminous Rocks in the Ozank(?)y Field,Ankara,Turkey

Bituminous rocks in the Ozank(?)y(Ankara) field are different from those of the Paleocene- Eocene Mengen and Güineytepe(Bolu) regions in metal enrichment levels.Organic carbon(C_(org)) content of organic material-rich rocks in the Ozank(?)y(Ankara) field is 3.66-40.72% wt averaging 14.34%.The dominant organic materials are algae/amorphous accompanied by minor amount of herbaceous material(The dominant kerogen type is Type-Ⅰwith a limited amount of Type-Ⅱkerogen.). The bituminous rocks in the Ozank(?)y field are enriched in heavy metals such as Ni,Mn,As and Cr.In comparison with the average enrichment values of elements,Ni,Mn,As and Cr in bituminous shales of the Ozank(?)y field are as about 4.38,14.93,10.90 and 5.58 times as average values.The average concentrations of these heavy metals are also as high as 215×10~(-6),828×10~(-6),58.54×10~(-6),and 148×10~(-6) respectively.In addition,sorption properties of clay and organic materials are also important for metal enrichments in the bituminous shales.     

地球化学方法在麻林桥低温热水勘查中的应用

应用地球化学方法是地热、温泉勘查中广泛采用的有效手段之一。以麻林桥低温热水为例，说明土壤中的汞、砷、硼微量元素的富集规律，这些微量元素对寻找地下导热构造有明显的指示作用。     

Early Cretaceous volcanic rocks and Early Cenozoic extrusions of Cape Mary, Schmidt Peninsula, north Sakhalin: Geochemical study

The Early Cretaceous volcanic rocks of the Mariisky sequence and Early Cenozoic extrusive-vent rocks of Cape Mary are exposed at the northwestern extremity of Schmidt Peninsula, north Sakhalin. In chemical composition, all the rocks are subdivided into four groups. Three groups include the volcanic rocks of the Mariisky sequence, which consists, from bottom to top, of calc-alkaline rocks, transitional calc-alkaline-tholeiite rocks, and incompatible element-depleted tholeiites. These rocks show subduction geochemical signatures and are considered as a fragment of the Moneron-Samarga island arc system. Trace-element modeling indicates their derivation through successive melting of garnet-bearing mantle and garnet-free shallower mantle sources containing amphibole; pyroxene; and, possibly, spinel. The mixed subduction and within-plate characteristics of the extrusive vent rocks of Cape Mary attest to their formation in a transform continental margin setting.     

Development of a Continental Volcanic Field: Petrogenesis of Pre-caldera Intermediate and Silicic Rocks and Origin of the Bandelier Magmas, Jemez Mountains (New Mexico, USA)

The Miocene–Quaternary Jemez Mountains volcanic field(JMVF) is the site of the Valles caldera and associated BandelierTuff. Caldera formation was preceded by > 10 Myr of volcanismdominated by intermediate composition rocks (57–70% SiO₂)that contain components derived from the lithospheric mantleand Precambrian crust. Simple mixing between crust-dominatedsilicic melts and mantle-dominated mafic magmas, fractionalcrystallization, and assimilation accompanied by fractionalcrystallization are the principal mechanisms involved in theproduction of these intermediate lavas. A variety of isotopicallydistinct crustal sources were involved in magmatism between13 and 6 Ma, but only one type (or two very similar types) ofcrust between 6 and 2 Ma. This long history constitutes a recordof accommodation of mantle-derived magma in the crust by meltingof country rock. The post-2 Ma Bandelier Tuff and associatedrhyolites were, in contrast, generated by melting of hybridizedcrust in the form of buried, warm intrusive rocks associatedwith pre-6 Ma activity. Major shifts in the location, styleand geochemical character of magmatism in the JMVF occur withina few million years after volcanic maxima and may correspondto pooling of magma at a new location in the crust followingsolidification of earlier magma chambers that acted as trapsfor basaltic replenishment. KEY WORDS: crustal anatexis; fractional crystallization; Jemez Mountain Volcanic Field; Valles Caldera; radiogenic isotopes; trace elements     

Trace变换的基本理论及其在地震勘探中的应用

Trace变换是一种新的图象重建工具,在图象重建方面已取得很好的效果。推导了Trace变换公式中的一个公式:∫(ε(t))rdtq的反变换公式,并结合τ-p变换中坐标系的转换关系,讨论了它在地震勘探中应用的可能性。对80道单一理论水平合成记录作了正、反变换的分析。从原记录和反变换记录中分别取道分析,分析结果表明对80道理论水平记录能很好的恢复。     

Modeling thermal deformation of VLBI antennas with a new temperature model

Temperature variations at very long baseline interferometry (VLBI) sites cause thermal deformations of the VLBI antennas and corresponding displacements of the VLBI reference points. The thermal deformation effects typically contain seasonal and daily signatures. The amplitudes of the annual vertical motion of the antenna reference point can reach several millimeters, depending on the design of the antenna structure, on the material, and on the environmental effects such as global station position, station height and climatology effects. Simple methods to correct this effect use the difference of the environmental temperature with respect to a defined reference temperature, the antenna dimensions, the elevation of the antenna, the material of antenna structure. Applying these simple models for thermal deformation in the VLBI data analysis improves the baseline length repeatability by 3.5%. A comparison of these simple models with local thermal deformation measurements at the antennas in Onsala and Wettzell show that the local measurements and the modeled corrections agree well when the temperature of the antenna structure is used, but agree less good when the surrounding air temperatures are used. To overcome this problem we present a method to model temperature penetration into the antenna structures, that allows to model thermal deformation effects that agree with the observed vertical deformation of the Onsala and Wettzell radio telescopes with a root mean square deviation of 0.07 and 0.13 mm, respectively. Possible implementations in the VLBI analysis are presented, and the definition of an adequate reference temperature is discussed.     

西秦岭北带泥盆纪Nereites遗迹相及其环境分析

西秦岭北带泥盆系舒家坝组下一中上部的巨厚陆源碎屑岩系中含有极丰富的遗迹化石,它们可为解释该组沉积环境提供重要信息:（1）由大量典型深水遗迹化石组成的Nereites遗迹相,可与世界各地浊积岩系和复理石相中的Nereites遗迹相进行对比,该遗迹相主要发育在浊流沉积区直至深海平原,其沉积水深最大可超过2000m;（2）舒家坝组的遗迹群落中,除大量属深水型分子外,还见有典型的浅水分子,两种水深性质不同的遗迹组合共生在一个沉积剖面,正是浊积岩系和复理石相才具有的独特分布特征;（3）根据沉积层序和遗迹组合的对比确认舒家坝组不存在风暴岩。     

Mineral magnetic and physical properties of surficial sediments and onshore samples from the southern basin of Lake Baikal, Siberia

Results of lithostratigraphic and mineral magnetic analysis of two surficial sediment cores (21 cm and 45 cm in length) collected from the Southern basin of Lake Baikal at a water depth of 1390 m, are presented. The sediments have been measured for a wide range of mineral magnetic parameters in order to assess their value in the identification of turbidite layers. Particle size and geochemical data are also presented and these explain some of the down core variations in magnetic mineralogy. It is suggested that changes in the particle size frequency distributions down core may be related to fossil diatom shells. One of the cores has been dated using ²¹⁰Pb. The sediment cores were cross-correlated using low frequency magnetic susceptibility (f) and these cores can also be correlated with a nearby core collected earlier in 1992. Changes in the magnetic parameters of lf, IRMs and HIRM₂₁₀ suggest that there are significant changes in the concentration of ferrimagnetic minerals in the sediment cores, indicating changing sediment sources and/or increasing concentrations of spheroidal carbonaceous particles and the dissolution of minerals through reduction below the oxidised layer within the sediment core.