The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.     

The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.     

北淮阳马畈加里东岩体的研究及其地质意义

位于北淮阳凹陷中部的马畈杂岩体,属于加里东期侵入体（角闪石４０Ａｒ／３９Ａｒ年龄为（４６２．７±１．４）Ｍａ）．化学成分显示该岩体具有钙碱性Ｉ型特点,形成于破坏性板块边缘的火山岛弧环境,定位深度约１０ｋｍ．根据岩体的应变分析、面理节理测量、包裹体测温,结合围岩宏观微观构造综合研究得出,马畈岩体至少经历了两次明显构造变形和３个阶段的抬升才剥露于地表．岩体主期隆升发生在侏罗纪之前,早于南部大别地块的主期隆升时间（Ｊ３—Ｋ１）,岩体的多期构造变形与北淮阳自早古生代以来的构造演化有着密切关系．     

雪峰山加里东造山运动及其体制转换

本文论述了雪峰山地区加里东造山运动的变形序列,加里东运动期间,至少存在３个连续的构造热事件。并且阐述了挤压体制向伸展体制的转换,形成低角度滑脱带,高角度正断层及变质核杂岩。     

塔里木盆地中央地区的断裂系统:几何学、运动学和动力学背景

塔中低凸起位于塔里木盆地中央隆起的中段,发育4组不同方向的断裂,以北西向的塔中Ⅰ号断裂带为主干断裂,其南的近北西向断裂和近东西向断裂与之组成"入"字形构造,向西撒开;剖面上则因塔中Ⅰ号断裂带活动强度自东向西减弱而出现不同的断裂组合样式。基于地层记录和区域演化分析了该区断裂系统的活动时期和活动方式,两次重大的挤压—剪切事件分别发生在奥陶纪末和晚志留-中泥盆世,因而塔里木盆地中央隆起可能是晋宁期山体在后期重新活动形成的加里东期陆内造山带。北西向断裂是二叠纪岩浆侵入或玄武岩喷溢的通道,之后全区断裂基本处于平静状态。结合塔里木周边造山带的演化,认为古生代—三叠纪时塔中地区的盆地发育主要受西昆仑造山带演化制约,同时叠加有古阿尔金剪切造山带的影响,这是为塔中地区特殊的构造位置决定的。侏罗纪—新近纪,该地的盆地主要与阿尔金断裂的剪切造山作用耦合发育,仅早白垩世时与塔北—库车地区同属南天山的"盆""山"系统。断裂的运动学特征取决于其动力学背景,实际上受制于邻侧的造山带发育。断裂系统的发育是塔中地区能形成复式油气田的关键条件之一,本文的研究对推进复式油气成藏的机理研究、明确近期的重点勘探靶区等有积极意义。     

广西钦甲花岗岩体岩石地球化学特征及成因研究

华南地区加里东期花岗岩远不如燕山期那么发育,位于广西西南部的钦甲岩体是较为著名的加里东岩体之一。钦甲岩体位于扬子板块西南缘,属早古生代花岗岩体。本文在前期年代学研究的基础上对钦甲岩体的岩石地球化学特征进行了分析探讨,其SiO2含量为65.94%~72.23%,全碱含量(K2O+Na2O)为6.27%~9.11%,K2O的含量普遍大于Na2O,A/CNK值为1.02~1.24,属弱过铝质花岗岩类。岩石稀土元素含量偏低,变化范围为17.18×10-6~128.33×10-6,其配分曲线呈轻稀土富集并缓向右倾斜、重稀土较为平坦、具较明显的铕负异常。微量元素以富集大离子元素Rb、Th,亏损Ba、Sr为特征,其形成可能和扬子板块与华夏板块之间的汇聚挤压有关,其源岩主要由含少量泥质的砂质岩组成,并可能有具Ce负异常的沉积物参与部分熔融。     

广西德保铜矿钦甲岩体Hf同位素特征及其对壳幔相互作用的指示

对广西德保铜矿钦甲岩体不同单元中的锆石进行了Hf同位素的研究,结果表明,钦甲岩体中锆石εHf(t)值变化范围为-17.0～+7.8,Hf同位素两阶段模式年龄(tDMC)范围为0.93～2.49Ga,峰值为1.3～1.6Ga,表明它们的岩浆源区主要以中元古代地壳物质为主,同时在成岩过程中有地幔组分的参与,属壳幔混源花岗岩,推测钦甲岩体可能形成于岩石圈伸展的壳幔混合作用环境。华南地区加里东期花岗岩中锆石Hf同位素特征,表明岩浆形成过程中具有明显的地幔物质加入,暗示华南地区在早古生代发生过强烈的壳幔相互作用。     

江西信丰桐木稀土矿区龙舌岩体的成岩时代及成矿条件分析

选择赣南离子吸附型稀土矿床产地——龙舌花岗岩体开展了锆石LA-ICP-MS定年工作。研究结果表明,岩体中的锆石晶型较完整,环带明显,属于典型的岩浆锆石;龙舌岩体之中粗粒斑状黑云母花岗岩形成于加里东期(206Pb/238U加权平均年龄为457.5±1.7Ma,MSWD=0.39)。加里东期的花岗岩可能是扬子陆块与华夏陆块拼接的结果,该花岗岩含有褐帘石等易风化的富稀土副矿物,经受多起构造事件,断裂发育,加之地处温热气候,遭受强烈的风化作用,有助于形成离子吸附型稀土矿床,因此对南岭离子吸附型稀土矿床的形成具有重要贡献。     

雪峰造山带中段地质构造特征

雪峰造山带的地质构造特征认识尚存在较多分歧。通过构造剖面测制并结合区域地质调查,对雪峰造山带中段东部怀化—两丫坪地区的形变类型、变形时代、变形强度、剖面结构以及构造变形的运动学特征、成因机制和构造体制等进行了较全面的分析研究,取得以下主要认识和进展:(1)雪峰造山带中段形变类型主要有板劈理、折劈理、褶皱及与褶皱同走向的大型膝褶带、逆断裂、正断裂、右行走滑断裂等;(2)加里东运动和早中生代构造运动(印支运动与早燕山运动)中均存在明显的挤压变形,构造体制均为NW—NWW向挤压,形成NE—NNE向褶皱和逆断裂,加里东运动尚形成了板劈理和大型膝褶带;(3)雪峰造山带中段以溆浦—靖州断裂为界分为东带和西带,分别为加里东期区域雪峰逆冲推覆构造的根带和中带。东带板劈理发育,西带板劈理不发育且上古生界与下伏地层产状相近,表明加里东运动中东带变形强度明显大于西带,不整合特征、抬升幅度、逆冲断裂的发育特征等表明早中生代构造运动中东带变形较强,而西带变形较弱;(4)劈理优势倾向以及褶皱轴面和逆断裂的倾向,反映雪峰造山带东带加里东运动和早中生代构造运动中均具有背冲构造样式,但早中生代背冲构造的中轴相对加里东期向西迁移25 km以上;(5)南华纪早期溆浦—靖州断裂以东大幅伸展断陷并接受巨厚沉积,晚古生代期间断裂东侧大幅伸展沉降而构成湘中沉积盆地的西边界,反映雪峰造山带东带为一块体强度低的构造薄弱带,这是其变形强度大于西带及成为雪峰推覆构造根带的主要原因。     

藏北羌塘中部日湾茶卡组物源--LA-ICP-MS锆石U-Pb年龄及稀土元素特征

在龙木错-双湖-澜沧江板块缝合带中段的冈玛错-日湾茶卡地区,近东西向展布着一条富含暖水型生物化石的早石炭世地层日湾茶卡组（C1r）。对日湾茶卡组砂岩中的碎屑锆石进行LA-ICP-MS U-Pb定年,分析结果显示存在325~400Ma、400~500Ma、500~600Ma、950~1100Ma、1400~1800Ma和大于1800Ma六个年龄区间;最年轻的碎屑锆石年龄为325 Ma,时代为早石炭世维宪期;碎屑锆石中362 Ma和454Ma的年龄峰值最明显,为龙木错-双湖-澜沧江洋岛弧消减事件和加里东运动的年龄记录,表明碎屑岩的物源区主要来自于扬子大陆周缘。结合古生物化石资料可知,日湾茶卡组属于欧亚大陆扬子型石炭纪沉积地层,为岛弧环境下的一套浅水台型沉积。