Petrological and Geochemical Constraints on the Evolution of the Alkaline Complex of Koraput in the Eastern Ghats Granulite Belt, India

The Koraput Alkaline Complex in the high-grade Eastern Ghats Belt, India, is synkinematically emplaced in a pull-apart structure and far from the Bastar cratonic margin. The suite comprises four distinct members, namely, mafic syenite, felsic syenite, nepheline syenite and perthite syenite. Fe-rich orthopyroxene rims on olivine in mafic syenite indicate iron-enrichment in the early stage of differentiation. With plagioclase of andesine composition it could be described as alkali-norite, the plutonic equivalent of hawiite. Felsic syenite with both alkali-feldspars and plagioclase of oligoclase composition could be described as two-feldspar syenite, the plutonic equivalent of mugearite. Albitic rims on nepheline indicates subsolvus reaction. Chemical trends in amphiboles and plagioclase feldspars, progressively more ferroan and more sodic respectively, are strong indications of mineral fractionation in the Koraput suite. Chemical trends in the variation diagrams are compatible with feldspar fractionation in the Koraput suite. A weak Fe-enrichment trend in the early stage of differentiation, as observed in the AFM diagram, is compatible with that of the alkali-basalt series. Nb anomalies, both positive and negative, are indicative of crustal contamination as expected in synkinematic plutons. In terms of Gondwana assembly and break up, the alkaline complexes are supposed to represent rift-related magmatism along the continental margin. In spite of petrological evidence of the magmatic character of the Koraput Complex, anorogenic setting is contra-indicated by mesoscopic and microscopic fabrics, more akin to synkinematic intrusion during F 2 folding in the host country rocks. The Proterozoic alkaline complexes in the Eastern Ghats Belt, could alternatively trace the path of moving Gondwana continent over mantle plumes.     

假雄牙鲆消化器官中碱性磷酸酶比活性的研究

碱性磷酸酶(alkaline phosphatases)是一种内源性酶，几乎存在于所有动物的细胞膜(plasma membrane)中，它在许多代谢活动中，如动物的生长、蛋自质的合成、营养成分的转运、类固醇的生成等方面都发挥着重要的作用(Ram et al.，1985)。因此，对于碱性磷酸酶的研究，有利于了解鱼类的消化生理，并有助于更深刻地理解鱼类体内营养成分的吸收和转运机制。假雄牙鲆是在雌性牙鲆的一定生长发育阶段，用人工诱导的方法使之性转化所获得的。对于假雄牙鲆的生理、生化特性的研究，至今还未见正式报道。本实验以一年龄假雄牙鲆为研究对象，研究了不同消化器官中碱性磷酸酶的比活性，并初步探讨了在不同发育时期碱性磷酸酶比活性的变化，从而能够更深刻地理解假雄牙鲆体内营养成分消化与吸收的过程和机制，并有助于牙鮃的人工培育。     

山东张里金矿碱性次火山岩特征与成矿作用

山东张里金矿床是与碱性次火山岩有关的、赋存于隐爆角砾岩体内的石英－ 冰长石－ 萤石型中低温热液矿床。岩石化学、稀土元素和同位素分析结果表明: 控矿岩石系列分为: ①高钾钙碱性岩石系列,SiO2 平均含量为57. 6%,稀土总量为373. 98 × 10 － 6 ～ 297. 43 × 10 － 6,δEu 为0. 85 ～ 0. 82,Sr = 0. 704 41; ②高钾碱性岩系列,SiO2 平均含量为56. 65%,稀土总量为371. 19 × 10 － 6 ～ 41. 62 × 10 － 6, δEu 为0. 89 ～ 0. 93,Sr = 0. 717 11。这两种控矿岩石系列分别由两个不同的幔源岩浆在上升过程中,各自经过长时期的分异作用,并且混染了部分壳源物质而成,其含矿热液来自碱性次火山岩。     

Collision‐related granite magma genesis,potential sources and tectono‐magmatic evolution: comparison between central,northwestern and western Anatolia (Turkey)

The central, northwestern and western Anatolian magmatic provinces are defined by a large number of late Mesozoic to late Cenozoic collision‐related granitoids. Calc‐alkaline, subalkaline and alkaline intrusive rocks in central Anatolia are mainly metaluminous, shoshonitic, I‐ to A‐types. They cover a petrological range from monzodiorite through quartz monzonite to granite/syenite, and are all enriched in LILE. Their geochemical characteristics are consistent with formation from a subduction‐modified mantle source. Calc‐alkaline plutonic rocks in northwestern Anatolia are mainly metaluminous, medium‐ to high‐K and I‐types. They are monzonite to granite, and all are enriched in LILE and depleted in HFSE, showing features of arc‐related intrusive rocks. Geochemical data reveal that these plutons were derived from partial melting of mafic lower crustal sources. Calc‐alkaline intrusive rocks in western Anatolia are metaluminous, high‐K and I‐types. They have a compositional range from granodiorite to granite, and are enriched in LILE and depleted in HFSE. Geochemical characteristics of these intrusive rocks indicate that they could have originated by the partial melting of mafic lower crustal source rocks.     

The Mazarrón basin,SE Spain: a study of mineralization processes,evolving magmatic series,and geothermal activity

The Miocene to Present Mazarrón basin provides a window on the metallogenic role of an evolving magmatic series. High-K calc–alkaline magmas gave rise to an important cluster of Pb–Zn–Ag–Cu vein and stockwork deposits emplaced in dacitic to rhyodacitic domes, part of a complex volcanic–metallogenic province (Au, Hg, Pb–Zn–Cu–Ag, Sn) stretching for ～150 km along the Mediterranean coast of SE Spain. By Pliocene time the former magmatic series had been replaced by intraplate alkaline basaltic volcanism, thus becoming the southern branch of the Western/Central Europe alkaline province. In terms of base metal sulphide deposits, this European province is barren, although it triggered widespread, CO₂-rich geothermal activity. Modern geothermal activity at El Saladillo (Mazarrón) resulted in the deposition of carbonate sinter deposits and formation of microbial mats. Proximal facies consist of millimetric to centimetric multicoloured layers of microbial mats, including yellow-orange thin bands of calcified bacteria and mineral growths of aragonite and calcite; green layers of live thermophilic Lyngbya-type cyanobacteria; black, degraded organic matter; and pyrite as the sole sulphide phase. Except for arsenic (37–63 μg g^?1), all of the studied trace elements (Ag, Ba, Bi, Cd, Cu, Pb, Sb, Se, and Sn) appear in remarkably low concentrations in the geothermal sinters. This is consistent with compositional data for the El Saladillo waters, with no significant metal concentrations. We present the first conceptual model (Miocene to Present) for the ore-forming processes, magmatism, CO₂ degasification, and geothermal activity for this realm. We argue that the time- and space-limited character of this volcanism (small, scattered outcrops), the deep magma emplacement level, the metal sulphide behaviour in alkaline basaltic magmatic chambers, and the dry character of these magmas prevented any metallogenic interaction between the chambers and the much shallower meteoric waters that drove the El Saladillo geothermal system and others of the same kind in Spain and elsewhere in Europe.     

西藏当惹雍错富钾和富钠碱性火山岩的矿物学研究及其成因指示

对青藏高原西南部当惹雍错地区的中新世超钾质粗面岩及共存的富钠质方沸石(霞石)响岩进行了详细的岩石学、矿物学研究,揭示出两套岩石具有不同的矿物学特征.钠质方沸石(霞石)响岩中橄榄石斑晶的熔体包裹体与钾质火山岩的成分相当,应属于早期残余的钾质岩浆,表明了钠质方沸石(霞石)响岩的形成晚于超钾质粗面岩.两类岩石的全岩化学成分、...     

西昆仑塔什库尔干苦子干碱性杂岩体的成因及其构造意义

苦子干碱性杂岩体是塔什库尔干新生代碱性岩带的主要组成之一,主要由霓辉正长岩、石英霓辉正长岩和碱性花岗岩组成。霓辉正长岩、石英霓辉正长岩和碱性花岗岩的SiO2含量差别较大,分别为50．26％～54．11％、59．74％～60．43oA、69．59％～72．13％;霓辉正长岩与石英霓辉正长岩的里特曼指数相近,分别为7．83～10．97、8．51～9．05,明显不同于碱性花岗岩（2．49～3．71）。这3种碱性岩石都表现出富集轻稀土,以及K、Rb、Sr、Ba等大离子亲石元素（LILE）,亏损Nb、Ta、Ti等高场强元素（HFSE）的特征。其中异常高的Sr、Ba和∑REE含量暗示可能还有富集地幔物质的加入。利用原位锆石LA—ICP—MS同位素测试方法,获得石英霓辉正长岩和碱性花岗岩的锆石U—Pb年龄分别为10．9±0．1Ma和11．9土0．4Ma,代表了岩石的结晶年龄;石英霓辉正长岩锆石εHf（t）值为-9．78～3．24,碱性花岗岩中锆石εHf（t）值为-13．54～5．78,均显示岩浆源区具有壳幔混合的特点。依据这些资料,并结合区域地质研究的综合分析,笔者初步提出西昆仑塔什库尔干苦子干碱性杂岩体的形成是由于青藏高原在～25Ma期间主体拆沉作用发生后,造成软流圈物质向北逃逸,并受到北面塔里木克拉通岩石圈山根阻挡而上涌,进而发生壳幔混合作用的产物。因此,该杂岩体是青藏高原大规模拆沉后浆活动的远程效应,且标志着研究区在～11Ma期间已处于伸展构造背景。     

山东郗山碱性杂岩体地球化学特征及其意义

郗山碱性杂岩体与稀土矿床的成因关系密切。通过系统的岩石地球化学研究,全面认识了该区碱性岩浆活动的性质、物质来源及构造背景。经研究发现,SiO2含量为65．08％～69．41％,属于酸性岩,全碱值（K2O＋Na2O）为8．16％～12．92％;在TAS图上,岩石样品全部落在碱性趋势线之上;微量元素的组成以富集大离子亲石元素（LILE）Ba、Sr,亏损高场强元素P、Nb、Ta、Hf为特征;稀土总量（EREE）为189．11×10^-6～2144．52×10^-6轻稀土强烈富集,亏损重稀土,以弱负Eu异常为主。郗山碱性杂岩体岩石属于碱性岩系列,成岩物质来源较深,与EMI富集地幔有关,并受到了地壳物质的混染,形成于引张型构造背景,为造山期后岩浆活动的产物。     

Trends in the training and employment of geoscientists in Australia from 1967 to 1978

There are now 14 universities and 8 colleges of advanced education in Australia with geology or earth science departments, which comprised 278 professional staff, 2020 undergraduates, and 556 graduate students in 1978. Academic staff, engaged in a wide range of research, represent less than 10 percent of the total number of Australian geoscientists. Almost all non‐academic employers (98 percent of the sample) presently accept a graduate with a B.Sc. (Hons) degree, while 85 percent accept a B.Sc pass degree. About 65 percent of non‐academic geologists work for industry, and the remainder are employed by government surveys and research organisations. Mining and mineral exploration employ 76 percent of the geologists in industry, followed by petroleum exploration with 11 percent. Geologists make up 83 percent of geoscientists in non‐academic employment, the remainder being geophysicists 15 percent and geochemists 2 percent. Information on vacancies available in early 1979 suggests that all the recent graduates would be absorbed by government and industry, and pointed to a resurgence in demand for qualified geoscientists. There has been striking growth in the number of consulting/contracting geological firms, with 65 firms employing 242 geoscientists replying to the 1978 census.     

Geochemical and isotopic evidence for the age,orogenic setting and petrogenesis of the Nychum Volcanic association,North Queensland

Rb‐Sr and K‐Ar age determinations agree with palaeobotanical evidence in assigning an age of 270 Ma (Lower Permian) to the Nychum Volcanics, North Queensland. Geological and geochemical evidence (moderate ‐REE, La/Yb, Th, Zr/Y, Hf/Yb, Sc/Ni) indicate that the volcanics were erupted on a thin, active continental margin. Five magma groups are present: high‐alumina basalts, andesite‐dacites, acid rocks, tholeiitic andesites, and pitchstone with a high La/Yb ratio. The high‐alumina basalts and calc‐alkaline andesites have a parent‐daughter (source rock‐partial melt) relationship. The acid rocks share high HREE, Zr, Hf, Zn, Sc, Fe/Mg and low Al with, and may be fractionated from, the tholeiitic subduction‐zone andesites. Low‐pressure fractional crystallisation is evident in all five magma groups.