Pre-Early Ordovician Cadomian arc-type granitoids, the Bolu Massif, West Pontides, northern Turkey: geochemical evidence

The West Pontides tectonic belt of northern Turkey comprises a Lower Ordovician–Lower Carboniferous transgressive sequence. A stratigraphic basement to this Paleozoic sequence is exposed in the Bolu area. The tectono-stratigraphy of the basement closely resemble that of the Cadomian belt of western Europe. Three rock units forming the basement imply development of an Andean-type active continental margin during the pre-Early Ordovician period. High-grade metamorphics (the Sünnice Group), granitoids (the Bolu Granitoid Complex) and evolved felsic meta-volcanic rocks (the Ça?urtepe Formation) are exposed unconformably beneath the Lower Ordovician fluvial clastics, between the Bolu-Yedigöller area, to the north of Bolu. The Bolu Granitoid Complex comprises a group of intrusive rocks of variable composition and size, generated through multiple episodes of magmatism, and is represented by two separate intrusive bodies within the study area, the Tüllükiri? Pluton in the west and the Kap?kaya Pluton in the east. Both plutons are mainly tonalite and granodiorite in composition. More felsic and mafic compositional varieties also occur. Major and trace element chemical characteristics of the granitoids, as well as biotite chemistry, indicate that these are volcanic arc-type granitoids and are products of an immature arc developed during early stages of a subduction. Furthermore, textural and chemical characteristics of the plutons show that these are subvolcanic intrusions, emplaced at shallow depths, and are calc-alkaline in composition. The granitoidic plutons intrude the Ça?urtepe Formation. The Ça?urtepe Formation is represented by arc-type volcanics and volcaniclastics. Both the Ça?urtepe Formation and the granitoids represent subduction-zone magmatism constructed on a continental crust, represented by the Sünnice Group. The history is very similar to Cadomian active margins as exposed in western Europe (i.e., the North Armorican and Bohemia massifs) and therefore the basement to the Paleozoic of the West Pontides is considered to be a preserved remnant of the Cadomian belt.     

Alkaline phosphatase in a littoral Mediterranean marine ecosystem: role of the main plankton size classes

This work investigates the alkaline phosphatase activity in a littoral marine ecosystem (Toulon Bay and Le Niel Bay, France) in order to study its biochemical characteristics with respect to pH, sea water composition and phosphate sensitivity. We also characterise the active forms in sea water and determine the extent to which zooplankton generate phosphatase activity with respect to other plankton classes. In Toulon Bay, phosphatase was produced mostly by the microplankton fraction (>90 μm), accounting for more than 90% of total activity. In contrast, most of the phosphatase activity in Le Niel Bay was generated by the nanoplankton fraction (5–90 μm) and the picoplankton fraction (0.25–5 μm). The microplankton enzymes had non Michaelis-Menten kinetics suggesting the involvement of multiple enzyme processes with distinct kinetic constants. This activity is in major part secreted into the sea water and is stimulated by the ionic strength and the pH of the sea water. Cypris larvae of the genus Balanus played a special role in this release. For the nanoplankton and picoplankton, part of this activity was due to non-secreted enzymes, probably bound to membranes or occurring intracellularly. Moreover, nano and picoplankton phosphatase required higher pH than microplankton enzyme. For all plankton size classes, there was no activity at low pH, suggesting that acid phosphatases were not involved in reactions with substrates dissolved in water.     

饲料中添加锌对牙鲆生长和生化指标的影响

含锌３７．５ｍｇ／ｋｇ的基础饲料中,分别加入锌０,１５,３０,５０,８０ｍｇ／ｋｇ,饲喂初重为３０．８５～３４．８５ｇ的牙鲆幼鱼１个月。结果表明,饲料中添加锌,鱼的增重率、肝脏锌含量、肠粘膜碱性磷酸酶活性都高于不添加组;且有随添加量加大而增加的趋势。当添加锌８０ｍｇ／ｋｇ时,此３项指标达到最大,分别为１１２．７％,４３．８ｍｇ／ｋｇ和１８．２８Ｕ／ｍｇ蛋白质。但添加锌没有影响鱼的成活率和肌肉锌含量。此结果说明,添加锌对牙鲆鱼苗具有促生长作用。建议在牙鲆的实用饲料中,锌添加量应大于８０ｍｇ／ｋｇ,锌的总含量应在１１９．２ｍｇ／ｋｇ以上。     

囊谦盆地新生代钾质碱性火山岩岩石地球化学特征

青海囊谦盆地发育一套渐新世（32～36 Ma）钾质碱性 火山 岩,主要岩石类型为粗 面安山岩、粗面英安岩。SiO2含量为43%～66%;总碱量（K2O+Na2O）较高,多为8%～ 10%, 多数K2O/Na2O＞1,属于钾质—超钾质碱性系列。研究表明,该区火山岩具有同源特征 ,源区 接近BSE组分,并含有一定比例的陆壳物质。源区可能经历了强烈混合均一化作用、交代作 用,是壳幔相互作用的产物。     

阿尼玛卿蛇绿岩带花岗—英云闪长岩锆石U—Pb同位素定年及大地构造意义

对阿尼玛卿蛇绿岩带布青山段花岗—英云闪长岩进行的锆石U—Pb同位素定年及岩石化学研究表明,该岩体锆石U—Pb年龄为402±24Ma,归属加里东末期,并非二叠-三叠纪同造山岩浆活动的产物;岩石属钙碱系列,具岛弧花岗岩特征,暗示着本区在早古生代发生过洋壳俯冲及岛弧岩浆活动事件,并为本区早古生代蛇绿岩的存在提供了佐证。     

Magmatic source enrichment by slab-derived melts in a young post-collision setting, central Mindanao (Philippines)

Central Mindanao was the locus of a Pliocene (4–5 Ma old) arc–arc collision event followed by basaltic to dacitic magmatism starting at 2.3 Ma, representing the most voluminous volcanic field in the Philippines. Lava compositions range from calc-alkaline to shoshonitic. Adakites and Nb-enriched basalts are among the magmatic products. All the lavas are Na-rich (up to 4.88%), with Na₂O/K₂O ratios from 2.5 to 6.5. Sr, Nd and Pb isotopic compositions are similar to MORB, except for some shoshonitic lavas that have slightly less radiogenic Nd ratios. K-enrichment in basalts can be related to both fractional crystallization (FC) at moderate pressures and to partial melting of an enriched source. Trace element systematics indicate that the sub-central Mindanao mantle is characterized by the presence of garnet, phlogopite, amphibole, and perhaps some titanate phase. The enrichment of this source is attributed to the interaction of slab-derived melts, i.e., adakites, with the arc mantle. This would explain the presence of Nb-enriched basalts, transitional adakites and high-magnesium andesites, as well as the bulk Na-enrichment and relatively unradiogenic character of the central Mindanao lavas. We envision an ion-exchange type of enrichment, in which the HFSE, LILE and LREE, mobilized during slab melting, are preferentially enriched in the metasomatized mantle, resulting in a diversity of post-collision magma compositions. The MORB-like isotopic signatures of the central Mindanao lavas preclude important contributions of slab-derived hydrous fluids, sediments, continental crust or an OIB-type contaminant. Slab melting after cessation of subduction is deemed possible by thermal rebound of previously depressed geotherms. Initial contributions to mantle enrichment in post-collision sites may thus come from slab melts. In most other cases of post-collision magmatism, however, this signature can be easily masked by enrichments coming from other sources, e.g., the continental lithosphere.     

THE IMPROVEMENT OF ALKALINE MEADOW BY ACCUMULATIVE SAND BY WIND IN THE SONGNEN PLAIN

In the Songnen Plain, there are 330,000 ha of alkaline meadow, many sand sources such as fixed dunes, semi-fixed dunes and sand hills, and rich wind force resources as well. Sand has been stopped naturally and A neurolepidium chinense has grown on alkaline patch of the plain. If we make use of the natural law and set up manmade obstacles in alkaline patches, we can use accumulative sand to cover alkali, improve alkaline meadow, restore A neurolepidium chinense vegetation to develop animal husbandry.     

LPHT metamorphism in a late orogenic transpressional setting, Albera Massif, NE Iberia: implications for the geodynamic evolution of the Variscan Pyrenees

During the Late Palaeozoic Variscan Orogeny, Cambro‐Ordovician and/or Neoproterozoic metasedimentary rocks of the Albera Massif (Eastern Pyrenees) were subject to low‐pressure/high‐temperature (LPHT) regional metamorphism, with the development of a sequence of prograde metamorphic zones (chlorite‐muscovite, biotite, andalusite‐cordierite, sillimanite and migmatite). LPHT metamorphism and magmatism occurred in a broadly compressional tectonic regime, which started with a phase of southward thrusting (D1) and ended with a wrench‐dominated dextral transpressional event (D2). D1 occurred under prograde metamorphic conditions. D2 started before the P–T metamorphic climax and continued during and after the metamorphic peak, and was associated with igneous activity. P–T estimates show that rocks from the biotite‐in isograd reached peak‐metamorphic conditions of 2.5 kbar, 400 °C; rocks in the low‐grade part of the andalusite‐cordierite zone reached peak metamorphic conditions of 2.8 kbar, 535 °C; rocks located at the transition between andalusite‐cordierite zone and the sillimanite zone reached peak metamorphic conditions of 3.3 kbar, 625 °C; rocks located at the beginning of the anatectic domain reached peak metamorphic conditions of 3.5 kbar, 655 °C; and rocks located at the bottom of the metamorphic series of the massif reached peak metamorphic conditions of 4.5 kbar, 730 °C. A clockwise P–T trajectory is inferred using a combination of reaction microstructures with appropriate P–T pseudosections. It is proposed that heat from asthenospheric material that rose to shallow mantle levels provided the ultimate heat source for the LPHT metamorphism and extensive lower crustal melting, generating various types of granitoid magmas. This thermal pulse occurred during an episode of transpression, and is interpreted to reflect breakoff of the underlying, downwarped mantle lithosphere during the final stages of oblique continental collision.     

Improvement of kerogen structural interpretations based on oxidation products isolated from aqueous solutions

A detailed investigation of kerogen oxidation products remaining in aqueous solutions after the usual isolation of degradation products by extraction with ether or precipitation, was carried out for the first time in kerogen structural studies. Three shale samples were investigated: Green River shale (type I kerogen), Toarcian shale, Paris Basin (type II), and Mannville shale, Canada (type III). The yields of acids from aqueous solutions were noticeable: 12.98, 15.32 and 22.32%, respectively, based on initial kerogens. Qualitative and quantitative capillary GC/MS analysis showed that the ratios of different kinds of identified acids depended much on the type of precursor kerogen. Some of the acids identified in aqueous solutions have not been found earlier among the degradation products of the same kerogen samples, or were obtained in different ranges and yields. Consequently, slight modifications were suggested of the image on the nature of various types of kerogens based on examination of ether-soluble acids only. Namely, slightly higher proportions of aromatic and alkane-polycarboxylic acids in the total oxidation products of both type I and type II kerogens indicated larger participation of aromatic and alicyclic and/or heterocyclic structures in these two kerogens. On the other hand, for type III Mannville shale kerogen, a somewhat larger share of aliphatic type structures was demonstrated.     

浙江建德新生代玄武岩源区特征及其成因

中国东南部浙江境内分布有大量新生代板内玄武岩，这些玄武岩的分布受到三条北东—南西向的断裂控制，将浙江玄武岩分为西部、中部、东部三个区域。其中，出露于浙江西部江山-绍兴断裂带的建德玄武岩是浙江境内最古老的新生代玄武岩（约40 Ma）。为进一步认识浙江境内新生代岩浆作用的本质，测定了建德玄武岩的元素组成和Sr、Nd、Hf、Pb同位素组成，并在与浙江境内其它新生代玄武岩对比的基础上，探讨它们之间的成因联系。建德玄武岩为碧玄岩，与浙江西部其它新生代玄武岩一样，碱性程度明显高于浙江中部和东部的新生代玄武岩（以弱碱性的碱性橄榄玄武岩和拉斑玄武岩为主）。这些玄武岩具有较低的SiO₂ (41.3~42.3 wt%）和Al₂O₃（9.70~12.6 wt%）含量，较高的MgO（8.90~15.6 wt%）、CaO（8.92~12.1 wt%）、TiO₂（2.78~3.18 wt%）和Fe₂O₃^T（14.1~16.2 wt%）含量以及较高的Ca/Al（1.02~1.16）比值。不相容微量元素组成上与火成碳酸岩具有亲缘性，即蛛网图上表现为明显的K、Zr、Hf、Ti的负异常（Hf/Hf*=0.74~0.77, Ti/Ti*=0.70~0.74），同时具有高的Zr/Hf比值（48.5~50.1），表明其地幔源区含有碳酸盐组分。建德玄武岩具有亏损的Sr-Nd-Hf同位素组成（⁸⁷Sr/⁸⁶Sr=0.7032~0.7034, εNd=5.85~5.95, εHf=7.78~8.56）和较高的²⁰⁶Pb/²⁰⁴Pb（18.491~18.554）、²⁰⁷Pb/²⁰⁴Pb（15.488~15.518）和²⁰⁸Pb/²⁰⁴Pb（38.387~38.523）比值。相比浙江中部和东部玄武岩，浙江西部玄武岩及建德玄武岩具有更高的碱含量、不相容微量元素含量、La/Yb比值和更明显的K、Zr、Hf、Ti负异常，表明浙江西部玄武岩是碳酸盐化地幔低程度熔融的产物。浙江新生代玄武岩的Ti/Ti*与Ba/Th、K/La比值之间较好的正相关性表明其源区存在两端元混合的特征。其中，以浙江西部玄武岩（包括建德玄武岩）为代表的地幔端元是由含碳酸盐的再循环洋壳熔融产生的碳酸盐熔体与亏损地幔反应形成的碳酸盐化地幔，以较低的Ba/Th、K/La和Ti/Ti*比值为特征。以浙江东部玄武岩为代表的地幔端元具有和碳酸盐化地幔端元互补的、较高的Ba/Th、K/La和Ti/Ti*比值，代表熔融残余的再循环洋壳。因此，浙江新生代玄武岩的地幔源区是不均一的，这种不均一性主要是由具有成因联系的两种端元组分所控制。