华北板块北缘中段早石炭世构造属性:察哈尔右翼后旗高分异Ⅰ型花岗岩地球化学的制约

察哈尔右翼后旗二长花岗岩岩体位于华北板块北缘中段.岩体富SiO₂、富K、富碱、低Ca和P、贫Fe和Mg,w(P₂O₅)与w(SiO₂)呈负相关,铝指数(A/CNK)为0.96~1.15,分异指数为90.36~92.96;主要造岩矿物为条纹长石、斜长石和石英,其铁镁矿物主要为黑云母,未出现碱性铁镁矿物和富铝矿物,副矿物为锆石、磁铁矿、磷灰石、榍石和钛铁矿;可见察哈尔右翼后旗二长花岗岩属高分异钙碱性I型花岗岩类.结合较低的w(∑REE)((46.8~94.4)×10^-6)、w(Th)((1.74~2.39)×10^-6)、w(U)((0.27~0.39)×10^-6)和微量元素判别图解,二长花岗岩岩浆源区可能为下地壳,源岩可能为岩石圈地幔.岩石轻重稀土分馏较强 ((La/Yb)_N= 6.52~28.39),δEu以正异常为主(0.83~3.51),富集大离子亲石元素(LILEs,Cs、Rb、Ba和K),亏损高场强元素 (HFSEs,Nb、Ta、P和Ti).地球化学特征反映了二长花岗岩具有火山弧岩石特征,且岩体侵入新元古界埃迪卡拉系什那干群,表明岩体形成于活动大陆边缘弧环境,其侵位反映了古亚洲洋的俯冲岩浆事件.     

南桥高度亏损N—MORB的发现及其地质意义

对赣西北九岭古岛弧西延部分的湖南浏阳南桥玄武岩进行了单颗粒锆石蒸发法2 0 7Pb/ 2 0 6Pb年龄测定 ,结果为 12 71± 2Ma。该玄武岩辉绿岩显示高度亏损的地球化学特性 :K2 O极低 ,不相容的高场强元素和稀土元素的丰度均低于 (少数接近 )N_MORB的平均丰度 ,εNd(12 71Ma)为 6 .86～ 8.98,具典型N_MORB特性 ,可能为沿古俯冲带分布的洋壳残片 ,为九岭古岛弧提供了新的证据。     

库布苏式金矿的发现过程及找矿方向

简述了库布苏金矿的地质特征，提出了在西部地区寻找该类矿床的找矿准则。该矿产于陆缘火山岩岩浆孤区，其成矿与强应变构造带及浅成、超浅成脉岩有关，有东准噶尔地区，强应变构造带与不同方向的断裂变汇地段、低绿片岩相带和金的化探异常应是优选找矿靶区的依据，次级脆性断裂破碎带、中性岩脉和蚀变应是找矿标志。     

Geochronology and Geochemistry of Early Cretaceous Granitic Plutons in the Xing’an Massif, Great Xing’an Range, NE China: Petrogenesis and Tectonic Implications

In this study, we present zircon U-Pb ages, whole-rock geochemical data and Hf isotopic compositions for the Meiguifeng and Arxan plutons in Xing'an Massif, Great Xing'an Range, which can provide important information in deciphering both Mesozoic magmatism and tectonic evolution of NE China. The zircon U-Pb dating results indicate that alkali feldspar granite from Meiguifeng pluton was emplaced at ～145 to 137 Ma, and granite porphyry of Arxan pluton was formed at ～129 Ma. The Meiguifeng and Arxan plutons have similar geochemical features, which are characterized by high silica, total alkalis, differentiation index, with low P_2O_5, CaO, MgO, TFe_2O_3 contents. They belong to high-K calc-alkaline series, and show weakly peraluminous characteristics. The Meiguifeng and Arxan plutons are both enriched in LREEs and LILEs(e.g., Rb, Th, U and K), and depleted in HREEs and HFSEs(e.g., Nb, Ta and Ti). Combined with the petrological and geochemical features, the Meiguifeng and Arxan plutons show highly fractionated I-type granite affinity. Moreover, the Meiguifeng and Arxan plutons may share a common or similar magma source, and they were probably generated by partial melting of Neoproterozoic high-K basaltic crust. Meanwhile, plagioclase, K-feldspar, biotite, apatite, monazite, allanite and Ti-bearing phases fractionated from the magma during formation of Meiguifeng and Arxan plutons. Combined with spatial distribution and temporal evolution, we assume that the generation of Early Cretaceous Meiguifeng and Arxan plutons in Great Xing'an Range was closely related to the break-off of Mudanjiang oceanic plate. Furthermore, the Mudanjiang Ocean was probably a branch of Paleo-Pacific Ocean.     

Every Cloud has a Silver Lining: Using Silver Concentration to Identify the Number of Sources of Lead used in Shang Dynasty Bronzes

The use of lead, some of which is characterized by a highly radiogenic signature, sharply distinguishes Bronze Age China from the rest of Eurasia. Scholars have long hypothesized that silver can offer an independent proxy to characterize lead minerals. The summary of silver distribution associated with Shang and Western Zhou bronzes in this paper reveals an important difference between the south(Sanxingdui, Hanzhong, Jinsha, Panlongcheng, Xin’gan) and the Central Plains. Correlating silver with ...     

Mineralogy and Geochemistry of the High‐Cr Podiform Chromitite from the Cuobuzha Ophiolite,Yarlung Zangbo Suture Zone,Western Tibet,China: Implication for its Origin

The Cuobuzha high-Cr chromitites in the western segment of Yarlung Zangbo Suture Zone of Tibet are mainly hosted in the harzburgites as massive type, which are characterized by high concentrations of platinum group elements(PGE) ranging from 380 to 577 ppb, and low Pd/Ir ratios(<0.1). In mid-ocean ridge basalts(MORB)-normalized spidergrams, chromites of the Cuobuzha chromitites are depleted in Al, Ga, V, Mg and Zn, and enriched in Mn and Cr, sharing similar patterns with those of ophiolitic b...     

新疆阿拉套山西段察哈乌苏二长花岗岩成因及构造意义

察哈乌苏岩体位于新疆西天山阿拉套山南缘的西段,大地构造位置属阿拉套山南缘泥盆纪—石炭纪弧后盆地,岩体主要由灰白色中粒二长花岗岩、灰白色中-细粒二云二长花岗岩组成。岩石地球化学数据显示,岩石中SiO2、Al2O3、碱含量较高,A/CNK=1.08～1.14,属过铝质高钾钙碱性花岗岩系列;轻稀土元素相对富集,重稀土元素相对亏损,稀土元素配分模式呈轻稀土富集的缓右倾型,具有明显的Eu负异常;强烈富集大离子亲石元素（LILE） Rb、Th、U、K、Hf,亏损高场强元素（HFSE） Ba、Nb、Ta、Sr、P、Ti;岩石具有较低的ISr值（0.701 5～0.702 6）。综合研究,表明察哈乌苏二长花岗岩为低Sr高分异S型花岗岩,兼具A型花岗岩的特征,是长石分离结晶的产物。二长花岗岩具有较高的正εNd （t）值（+0.37～+1.18）;高的Th、Ta含量及Th/Ta值（6.12～8.54）指示岩浆源区为亏损地幔,但受到古老地壳物质同化混染的影响。构造判别图解中所有样品落入火山弧花岗岩和同碰撞花岗岩的交界部位,更靠近同碰撞花岗岩区域。察哈乌苏岩体的侵位时代为313 Ma,结合区域地质背景,笔者认为伊犁微板块在310 Ma前已与准噶尔微板块碰合,北天山洋盆闭合时限早于晚石炭世末,310 Ma以后,阿拉套山地区逐渐进入后碰撞伸展阶段。因此,察哈乌苏二长花岗岩应为后碰撞花岗岩,岩体形成于同碰撞挤压向后碰撞伸展转换过渡阶段的张性环境,是幔源玄武质岩浆底侵和发生ACF作用的结果,其构造背景可能为活动大陆边缘。     

北山白头山铷矿赋矿花岗岩锆石U-Pb年龄、分异演化过程及对铷成矿的约束

白头山铷矿位于北山造山带,为近年来新发现的超大型铷矿,含石榴子石白云母花岗岩是其重要的赋矿岩体,对于理解铷富集成矿机制具有重要意义。白头山含石榴子石白云母花岗岩具有高硅(SiO2为73.56%~75.60%)、富碱(Na2O+K2O为8.84%~10.39%)、富铝(Al2O3为14.41%~15.01%),低Mg、Fe、Ca、P和Ti的特征,铝饱和指数较高(A/CNK=0.98~1.14)。微量元素方面,白头山含石榴子石白云母花岗岩富集Rb、Th、U、Ta,相对亏损Ba、Sr、P、Ti,具有明显的负Eu异常(Eu/Eu*为0.02~0.03)。岩石学、矿物学和地球化学特征指示,白头山含石榴子石白云母花岗岩属于高分异S型花岗岩,在岩浆演化过程中该花岗岩体系可能发生了云母、斜长石、锆石等矿物的结晶分异作用。稀土元素总量较低(32.06×10-6~45.33×10-6),具有明显的四分组效应(TE1.3=1.28~1.31),结合特征性元素对(Zr/Hf、Nb/Ta、Y/Ho、K/Rb)发育的non-CHARAC(不受离子电荷半径控制)行为,反映其经历了强烈的分异演化与熔流体作用。高分异花岗岩的强烈分异演化和熔流体作用是白头山铷矿富集成矿的关键控制因素。锆石U-Pb测年显示,白头山含石榴子石白云母花岗岩形成年龄为226±3.8 Ma,结合前人资料,表明印支期是东天山—北山地区高分异花岗岩和伴生稀有金属形成的重要阶段,为研究区稀有金属找矿提供了新的方向。     

喜马拉雅淡色花岗岩成因与稀有金属成矿潜力

喜马拉雅淡色花岗岩世界瞩目,具有重要的理论研究和找矿意义,但是其成因争议较大。本文统计了两千余件样品的全岩主微量地球化学、Sr-Nd-Pb-Hf同位素、锆石/独居石/磷钇矿等副矿物原位U-Pb年龄和锆石Hf同位素等,试图全面地总结喜马拉雅淡色花岗岩的研究进展和现状。喜马拉雅淡色花岗岩分为南北两带,北带花岗岩主要出露于特提斯喜马拉雅和片麻岩穹隆中,而南带花岗岩主要发育在高喜马拉雅顶部和东-西构造结中。从北往南,成岩时代逐渐变新;南北两带均以二云母花岗岩和(石榴石-电气石)白云母花岗岩为主,两期(始新世和中新世)中-基性岩脉和埃达克质岩主要在北带中发育。新生代岩浆活动分为5个阶段：49~40 Ma、39~29 Ma、28~15 Ma、14~7 Ma、6~0.7 Ma,分别主要与新特提斯洋壳板片断离、印度陆壳板片的低角度俯冲、断离或回撤、南北向撕裂(裂谷)和东西构造结的快速隆升有关。喜马拉雅淡色花岗岩起源于高喜马拉雅杂岩系的不一致(不平衡)部分熔融,并经历了矿物分离结晶的高分异演化。淡色花岗岩属于强过铝质岩石,具有高Si、K、Na,低Ca、Fe、Mg、Ti、Mn,高的Rb/Sr、Y/Ho值,低的Th/U、Nb/Ta、Zr/Hf、K/Rb值,稀土元素总量较低,负Eu异常明显的地球化学特征。随着成岩时代变新,Sr-Nd-Pb-Hf等同位素都指示岩浆源区中古老地壳物质的占比逐步增加。喜马拉雅淡色花岗岩/伟晶岩中Li、Be、W、Sn、Ta、Cs和Rb等稀有元素的富集系数大于10,伟晶岩属于典型的LCT型伟晶岩。喜马拉雅新生代淡色花岗岩带有望成为一条新的世界级的Li-Be-Sn-W-Ta稀有金属成矿带。     

Study on characteristics of 3-D translating-pulsating source green function of deep-water havelock form and its fast integration method

The singularities, oscillatory performances and the contributing factors to the 3-D translating-pulsating source Green function of deep-water Havelock form which consists of a local disturbance part and a far-field wave-like part, are analyzed systematically. Relative numerical integral methods about the two parts are presented in this paper. An improved method based on LOBATTO rule is used to eliminate singularities caused respectively by infinite discontinuity and jump discontinuous node from the local disturbance part function, which makes the improvement of calculation efficiency and accuracy possible. And variable substitution is applied to remove the singularity existing at the end of the integral interval of the far-field wave-like part function. Two auxiliary techniques such as valid interval calculation and local refinement of integral steps technique in narrow zones near false singularities are applied so as to avoid unnecessary integration of invalid interval and improve integral accordance. Numerical test results have proved the efficiency and accuracy in these integral methods that thus can be applied to calculate hydrodynamic performance of floating structures moving in waves.