Geochemical Features and Sources of Metasedimentary Rocks of the Western Part of the Tukuringra Terrane of the Mongol–Okhotsk Fold Belt

This work presents the results of geological, geochemical, Sm–Nd isotope-geochemical studies of metasedimentary rocks of the Teploklyuchevskaya, Garmakan, and Algaja formations of the Tukuringra Terrane of the eastern part of the Mongol–Okhotsk fold belt, as well as U–Th–Pb geochronological (LA-ICP-MS) studies of detrital zircons from these rocks. It is established that the lower age boundary of formation of the protolith of metasedimentary rocks of the Teploklyuchevskaya Formation is about 243 Ma (Middle Triassic); those of the Garmakan and Algaja formations are ~175 Ma (Lower–Middle Jurassic boundary) and ~192 Ma (Lower Jurassic), respectively. This makes it possible to correlate the Teploklyuchevskaya, Garmakan, and Algaja formations with the youngest sedimentary complexes of the eastern part of the Mongol–Okhotsk fold belt. In terms of geochemistry, the protoliths of metasedimentary rocks of the above-mentioned formations are the most similar to sedimentary rocks of island arcs and active continental margins. The source terrigenous material was transported from the southern frame of the Mongol–Okhotsk fold belt. It is not improbable that Lower Mesozoic deposits of the western part of the Tukuringra Terrane, in particular, and the eastern part of the Mongol–Okhotsk fold belt, as a whole, are relics of residual basins, preserved in “gaps” in the collision zone between the southern margin of plates of the North Asian Craton and the Amur Superterrane.     

Geological and Geochemical Characteristics of Early Cretaceous Mafic Dikes in Northern Jiangxi Province, SE China and Their Geodynamic Implications

The development of Early Cretaceous mafic dikes in northern and southern Jiangxi allows an understanding of the geodynamic setting and characteristics of the mantle in southeast China in the Cretaceous. Geological and geochemical characteristics for the mafic dikes from the Wushan copper deposit and No. 640 uranium deposit are given in order to constrain the nature of source mantle, genesis and tectonic implications. According to the mineral composition,the mafic dikes in northern Jiangxi can be divided into spessartite and olive odinite types, which belong to slightly potassium-rich calc-alkaline lamprophyre characterized by enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE), large depletion in high strength field elements (HSFE) and with negative Nb, Ta and Ti anomalies, as well as 87Sr/86Sr ratios varying from 0.7055 to 0.7095 and 143Nd/r44Nd ratios varying from 0.5119 to 0.5122.All features indicate that the magma responsible for the mafic dikes was derived mainly from metasomatic lithosphere mantle related to dehydration and/or upper crust melting during subduction. Differences in geochemical characteristics between the mafic dikes in northern Jiangxi and the Dajishan area, southern Jiangxi were also studied and they are attributed to differences in regional lithospheric mantle components and/or magma emplacement depth. Combining geological and geochemical characteristics with regional geological history, we argue that southeast China was dominated by an extensional tectonic setting in the Early Cretaceous, and the nature of the mantle source area was related to enrichment induced by asthenosphere upwelling and infiltration of upper crust-derived fluids responding to Pacific Plate subduction.     

DTA Characters of Biotites of Different Genetic Types and Their Implications

A new method is proposed to determine the genetic types of granites.Based on detailed DTA measurements on biotite in granites from south China and the Sanjiang area,characteristic thermal properties are presented for biotites of different origins.Mechanisms are discussed for the differences in thermal behavior of biotite in terms of chemical composition,crystal structure,ordering and polytypism.These characteristic thermal parameters of biotite can be used to shed light on granie genesis with the advantages of rapidness ,simplicity and economy.     

Geological and Geochemical Characteristics and Petrogenesis of the Anqing—Lujiang Quartz Syenite Rock Belt,East China

The Anqing-Lujiang quartz syenite rock belt consists of the Huangmeijian, Chengshan and Dalongshan composite batholiths which intruded into the Mesozoic strata. The country rocks were subjected to thermal contact metamorphism with little sign of folding and regional metamorphism. The rock belt is Late Yenshanian in age with a Rb-Sr isochron age of 135 Ma. Major rock types are quartz syenite and, to a lesser extent, syenite porphyry and alkali feldspar granite. Rock-forming minerals are dominantly potash feldspar (more than 50%) and lesser amounts of plagioclase and quartz. Mafic minerals, mostly Mg-biotite with lesser amounts of amphibole and pyroxene, are rare. Occasionally, alkalic mafic minerals (aegirine, riebeckite) are found. Characteristic accessary minerals of the earlier intrusives are magnetite, sphene and apatite and those of the later intrusives are ilmenite and zircon. Typologic distribution and evolutionary trend of zircon population are very similar to those of granites of mantle origin as suggested by Pupin, J. P. Petrochemically, the rock belt is poor in Ca but rich in alkali and Al with Na₂O+K₂O > 10%. It belongs to the K-Na transitional series, with a high alkalinity ratio (A. R. = 3–7) and a K /Na (atom) ratio close to unity. Rocks in the belt are rich in REE which tends to decrease from the early to the late stage, belonging to LREE type. The initial Sr ratio is 0.7078–0.7064. The rock belt is the Mesozoic anorogenic product of alkalic magmatic activity from a deep-seated source. According to a mantle-crust mixing model for Sr and Pb isotopes, it is estimated that 60.2–53.8% of the materials has been derived from the mantle. Additionally, its rich alkali, poor water content and anorogenic characteristics suggest that the belt is similar to the A-type granites.     

Ocean Ridge Granite and Its Geochemical Characteristics in Western Qinghai—Xizang Plateau

In our work,ocean ridge granite,i.e., Oytan plagiogranite massif,was discovered in western Qinghai-Xizang plateau.It intruded into the basic lava of the Oytag ophiolite suite and it was formed a little later than the (ultra)mafic rocks of the Oytag ophiolite suite.The Oytang plagiogranite possesses the geochemical characteristics of mantle-source granite and was formed in the “supre-subduction zone”(SSZ)ocean ridge environment,like the ocean ridge granite of Troodos,Cypus.     

Geodynamic Background of the Mesozoic Intracontinental Magmatism in Southeast China

The authors have proposed a dynamic model in this paper based on the ages,rock series and associations,Sr-Nd isotopic signatures of the Mesozoic intracontinental magmatism overlying the Cathaysian and Yangtze blocks.The model describes the relation of intracontinental collision and subduction in the Tethyan tectonic regie with Paleo-Pacific oceanic plate sudbuction-strike slip-extension in the Pacific tectonic regime.During 220-150Ma,the horizontal collision between the North China block and the Yangtze block,as well as the intracontinental subduction of some divergent microcontinental terranes in the southwestern part of South China are ascribed to the influence of the Tethyan tectonic regime,giving rise to a volume of high-Isr and low-εNd(t) S-type granites only in the Cathaysian Block.During 145-90Ma,under the geodynamic backgound of subduction-strike slip-extension of the Paleo-Pacific oceanic plate on the basis of the deep tectonic process in the Tethyan tectonic regime,high-K,alkalirich calc-alkaline and shoshonitic volcano-plutonic complexes were generated in the Yangtze block,and high-K calc-alkalic and bimodal volcano-plutonic complexes were generated in the Cathaysian block.The occurrence of A-type peralkaline granites in the coastal areas of South east China indicates the end of Mesozoic intracontinental magmatism.     

Structural Geochemical Study of the Yuxi Fold-Thrust Belt in the Southern North China Plate

The gigantic fold-thrust fracture belt that ex-tends for 900 kmto the NWin the southern NorthChina plate strides across three provinces : Shaanxi ,Henan and Anhui .It is one of the most characteristicstructural deformations in the North China plate .Along this structural belt a series of i mportantcoalfields occur ( e . g. Pingdingshan, Queshan,Huainan) inthe southernmost edge of the North Chi-na coal-concentrating basin. Consequently ,this beltis not only of key value for research onthe…     

Geochemical and Sr–Nd isotope evidences of the suprasubduction nature of mesozoic magmatism in the Mongol–Okhotsk Sector of the Pacific Fold Belt

In this article we present geochemical and isotope characteristics of rocks of the Unerikan, Selitkan and Aezop–Yamalin volcano–plutonic zones of the eastern termination of the Mongol–Okhotsk Orogenic Belt. The obtained data demonstrate that the Mesozoic igneous rocks of the Mongol–Okhotsk sector of the Pacific Folded Belt were formed due to the melting of the continental crust in a tectonic setting corresponding to a suprasubduction one.     

Comparative Geochemical Characteristics and Genesis of Large Polyphase Plutons in the Cores and on the Periphery of the Mongol–Okhotsk Fold Belt Magmatic Areas of Different Ages

Doklady Earth Sciences - The early Mesozoic Baga-Khentei pluton is a part of the Daurian–Khentei batholite that was formed under the impact of the Mongolian plume on the lower horizons of the...     

Geochemical Characteristics of the Plagiogranites in the Vicinity of Bingdaban,Central Tianshan

The tectonic and geochemical characteristics suggest that the plagiogranites exposed in the vicinity of Bingdaban on the northen margin of the central Tianshan uplift zone show a distinct mantle-source character, and their enrichment in LREE and selected enrichment in LILE(large ion lithophile elements)reflect a setting related to an arc tectonic regime.These rocks represent the products formed at shallow levels from mantle-derived magmas modified with subduction components(or super crustal rocks).     

华北克拉通北缘西拉沐沦钼多金属成矿带钼矿化类型、特征及地球动力学背景

最近,在华北克拉通北缘,沿东西走向的西拉沐沦构造带两侧异军突起地出现了一个400多千米长、300千米宽的钼矿带,短短4年时间已经发现了10余个大型-中型钼矿床,显示了巨大的资源前景。钼矿床的空间分布受区域东西向、北东向及北西向断裂联合控制,钼矿床的形成与中生代的中酸性侵入体关系密切,矿床产于花岗岩体中、斑岩体内外接触带或附近,矿床类型以斑岩型、石英脉型、火山热液型及云英岩型为主。空间关系表明钼矿床的形成主要与中生代富硅、富钾酸性侵入岩有关。成矿年代学研究表明,西拉沐沦成矿带钼矿具有三期成矿作用：包括245Ma、150Ma和138Ma。其对应的成矿动力学背景为印支期华北板块与西伯利亚板块碰撞造山后伸展阶段和燕山期中国东部构造大转折期。其中,印支期的成矿作用和相应的岩浆活动在以往的工作中较少论及。     

华东地区花岗岩类成因类型及其与铀成矿的关系

本文对华东地区的花岗岩类按改造型 变质混合交代型、重熔型和同熔型———同熔型 (Ⅰ型 )、深源分异型 (A型 )进行了成因分类 ,并对各类花岗岩的岩石化学成分、岩石学特征、副矿物、稀土元素、锶、氧同位素等特征进行了较为详细的论述 ,列举了各类花岗岩的分布地区和代表性岩体 ;论述了各类花岗岩的空间分布与铀矿床产出的关系 ,指出重熔型花岗岩是铀矿床产出的主要岩体类型 ,其次是深源分异型 (A型 )花岗岩。变质混合交代型和同熔型 (Ⅰ型 )花岗岩只有铀矿点或矿化点产出。文章最后系统地总结了改造型与同熔型花岗岩的铀矿化特征。     

大陆造山带地球化学研究：Ⅰ 岩石构造环境地球化学判别的改进

本文讨论了如何改进岩石构造环境的地球化学判别方法及其应用于研究造山带构造演化的问题，在论述了岩石地球化学特征与形成构造环境关系实质的基础上，提出了优选判别指示元素，参数和方法的准则及应用实例；并提出采用岩套内岩类配套及相邻相造期岩套或岩石建造时空配套综合分析途径的建议，从解决某些岩石化学特征在反映构造环境方面存在的多解性问题，推动造山带构造演化细节的深入研究。     

滇西三江造山带中南段地球化学分区特征

正中国多类型区域地球化学调查工作获得了丰富的数据资源,其提供的全方位信息亦在矿产资源勘查等方面发挥了重要作用(Wang Xueqiu et al.,2007)。近年来,学者们尝试利用区域性化探数据进行元素的地球化学分区,取得了较好的效果(汤金来等,2016)。三江造山带是我国重要的成矿带之一,其区域化探工作始于上世纪60年代,并阶段性完成了1:50万、1:25万和1:20万多尺度     

过铝花岗岩的成因类型与构造环境研究综述

概述了过铝花岗岩类的成因类型及形成的构造背景,特别介绍了过铝花岗岩岩浆的来源及其鉴别标志,指出过铝花岗岩岩浆按物质来源可分为壳源、幔源和壳幔混源三种类型,是地壳、地幔以及地壳物质与地幔物质相互混合和相互作用的结果,各种不同类型之间可能存在一种地壳源与地幔源之间的连续谱系,并简要介绍了CPG和MPG两种主要过铝花岗岩的成因机制.提出了过铝花岗岩形成环境的综合判别准则,指出过铝花岗岩不仅可以形成于碰撞造山过程中的挤压性构造环境,而且可以形成于与岩石圈伸展作用相关的张性构造环境.     

关于造山带花岗岩类填图方法的讨论——以西秦岭天水地区为例

花岗岩类的分类理论决定其填图方法.现行的单元-超单元填图方法是依据花岗岩类的I型、S型分类理论和同源岩浆演化理论而建立的.由于同源岩浆演化理论的不完善性,造山带地壳结构及地质构造特征的复杂性、地质作用过程的多样性,导致了形成花岗岩类源岩组分的复杂性,使得I型、S型分类在造山带具有不确定性,因而单元-超单元填图方法在造山带实践中存在较多问题和矛盾.造山带花岗岩类填图方法应以基本岩石分类方案为依据,以野外可识别、易掌握的客观岩石学、矿物学、组构学为准则, 客观、真实地反映造山带花岗岩类的特色.     

江南造山带雪峰隆起区元古宙浊积岩沉积构造背景的地球化学制约

江南造山带雪峰隆起区元古宙浊积岩的地球化学组成良好地反映了沉积盆地的板块构造性质,并为解释区域大地构造的性质和演化提供了有用的信息。中元古代冷家溪群和新元古代板溪群(包括下部马底驿组和上部五强溪组)地层在主元素成分上无明显区别,总体上以中等SiO2含量和K2O/Na2O比值以及较高的(Fe2O3+MgO)含量为特征。稀土元素球粒陨石标准化曲线与典型的后太古宙页岩(如PAAS或NASC)和上陆壳相似,以轻稀土富集、显著的铕负异常和重稀土平坦为特征。大离子亲石元素和铁镁族元素的含量中等。主元素和微量元素特征指示了研究区元古宙浊积岩很可能代表了一套活动大陆边缘弧后沉积盆地的产物。陆内裂谷盆地模式对于解释新元古代华南地区的构造性质和演化可能并不合适。华夏陆块与扬子陆块的拼接以及Rodinia超大陆的最终形成可能发生在约0.8Ga左右的晋宁(雪峰)造山运动期,而不是全球Grenville造山期末的四堡(东安)运动期。     

阿尔金南缘构造带西段辉绿岩墙群的地球化学特征及构造环境

对阿尔金南缘构造带西段辉绿岩墙群的岩石学和地球化学的详细研究表明,该区辉绿岩墙群为拉斑系列岩石,其主量元素以中等TiO2(1.19%～1.59%)、高MgO(5.51%～7.88%)、贫K2O(0.04%～0.84%)和P2O5(0.10%～0.20%)、Na2OK2O为特征;高场强元素(HFSE)丰度特征显示其为E-MORB型或过渡型玄武岩质岩石;稀土元素总量相对较高,轻重稀土元素分馏不显著[(La/Yb)N=1.93～3.61,LREE/HREE=3.01～4.10],在球粒陨石标准化配分模式图上呈略富集型.结合玄武岩构造环境判别图解综合分析推测,它们可能形成于一种裂谷向MORB环境过渡的构造环境,即初始小洋盆构造环境.     

Ages and geodynamic settings of Xilamulun Mo–Cu metallogenic belt in the northern part of the North China Craton

The Xilamulun belt along the northern part of the North China Craton is located in eastern segment of the Central Asian Orogenic Belt and has great economic potential for Mo–Cu mineralization. More than ten medium to large ore deposits have been discovered in this region in the recent years. The major types of mineralization type include porphyry (Chehugou Mo–Cu, Kulitou Mo–Cu, Xiaodonggou Mo and Jiguanshan Mo), quartz vein (Nianzigou Mo, Xinjing Mo), epithermal (Hongshanzi Mo–U) and alteration assemblage (Liulingou Mo). The timing of mineralization was previously thought to be Yanshanian (208–290 Ma), however, Indosinian (260–208 Ma) ages for intrusions and mineralization have been recognized in recent years. Based on geochronologic data and regional geological evidence, it is suggested that the mineralization in the Xilamulun belt was formed during multiple events. The mineralization processes are related to a post-collisional extension stage (~ 258–210 Ma) with the generation of the porphyry molybdenum–copper deposit, a tectonic stress transformation from NS to EW (~ 185–150 Ma) that gave rise to vein or porphyry molybdenum deposit, and a lithospheric thinning stage (~ 140–110 Ma) with porphyry molybdenum deposit.     

Geochemical and Sr-Nd isotopic evidence for origin and evolution of the Miocene Pangeon granitoids,Southern Rhodope,Greece

The Sr-Nd isotopic ratios of selected post-collisional, calc-alkaline, I-type granitoids from the Pangeon pluton, intruding the lower tectonic unit (LTU) in the Southern Rhodope in the Miocene, support the existence of two types of granitoids (PTG porphyritic tonalite granodiorite and MGG biotite granodiorite to two-mica granite) unrelated by crystal fractionation and likely derived by partial melting of the same source under different P-T conditions. The Sr-Nd isotopic ratios of mafic enclaves in the granitoids as well as metamorphic rocks from the LTU have also been determined. At 22 Ma, the IR_Sr range between 0.706850 and 0.708381, whereas the ε_Nd(22) range from –3.86 to –1.05, with no relationship to granitoid types. The relationships between Sr and Nd isotopes as well as these isotopes and SiO₂ provide evidence of contamination of mafic melts by interaction with crust during magma differentiation. Both partial melting and AFC processes (r = 0.2) may account for compositional variations in the Pangeon magmas. The mafic enclaves display IR_Sr from 0.706189 to 0.707139, and ε_Nd(22) from –2.29 to –1.94, similar to the granitoids, supporting the hypothesis of a common origin. Amphibolites inferred to be subduction-enriched metabasalts under-plated crust during old subduction can represent the source of the Pangeon melts. The T_DM of the Pangeon granitoids is in the range 0.7–1.1 Ga for the inferred extraction age of the LILE-enriched subcontinental lithospheric mantle source. The upper crustal geochemical signatures and the relatively small isotopic composition of the Pangeon granitoids make these rocks similar to the coeval eastern-Mediterranean lamproites emplaced within the same geodynamic setting; this prompts similar melt sources. Lastly, the Pangeon granitoids display geochemical characteristics, isotopic ratios, and T_DM also similar to other Tertiary magmatic rocks from the Southern Rhodope and Biga peninsula, western Anatolia, suggesting a similar tectonic environment and co-magmatic evolution throughout the area.