二长石地质温度计在估算乌拉山金矿碱性长石形成温度中的应用_英文_
研究岩楽岩的金钥匙：角闪石-斜长石矿物温压计
文章编号：1006 - 446X (2016 ) 01—0038 - 04研究岩楽岩的金钥匙：角闪石-斜长石矿物温压计孟子岳朱飞霖张凯亮(成都理工大学地球科学学院地球化学系，四川成都610059)摘要：角闪石-斜长石温压计具有数据易得、结果可靠和应用广泛的优点，该文系统总结了角闪石-斜长石温压计的计算原理及适用条件，以及该温压计在计算岩浆体系成岩成矿的温度、压力，进而估算岩浆侵位深度及上升速率方面的应用，揭示了其在岩浆演化过程中的重要意义。
关键词：角闪石-斜长石温度计；角闪石全铝压力计；适用条件；应用实例中图分类号：T Q056.il 文献标识码：AThe Key to Research the Magmatic Rocks：Hornblende - plagioclase GeothermobarometerMENG Ziyue,ZHU Feilin,ZHANG Kailiang(Department of Geochemistry,Chengdu University of Technology,Chengdu610059,China)Abstract:Hornblende- plagioclase geothermobarometer has the advantages of the data acquired easily, reliable results and wide application.This paper summarizes the calculation principle of hornblende- plagioclase thermobarometry and applicable conditions.Besides it elaborates the use of thermobarometry in calculating the temperature and pressure of the magma system,then,estimating the depth and the rising rate of magma intrusion.It also reveals the important significance of hornblende - plagioclase geothermobarometer in the research of magma evolution.Key words：hornblende plagioclase thermometer;hornblende geobarometer;applicable conditions; application examples角闪石和斜长石是许多岩浆岩中常见的造岩矿物，由此两种矿物组成的角闪石-斜长石温压 计较其它矿物温压计具有数据易得、结果可靠等优点，并且该温压计在较大的温度(400 ~1 150 ^)、压力（0.1 ~2.3 GPa)范围内都比较稳定[1]。
锆石在地质研究中的应用
2021.08科学技术创新锆石在地质研究中的应用夏浪(成都理工大学,四川成都610000)锆石一直被视为具有高度稳定性的矿物,具有能持久保持矿物形成时的物理化学特征,富含U 、Th 等放射性元素、离子扩散速率低、封闭温度高等特点,因此被广泛于岩石学、地球化学研究中。
近年来微区定年技术发展,锆石更加成为了U -Pb 定年的理想对象。
本文从锆石岩相学、地球化学、包裹体等方面阐述锆石在地质领域研究中的应用方向。
1锆石矿物学和岩相学特征锆石的化学式为Zr Si O 4,含有H f ,Th ,U 等混入物,在岩浆岩矿物中含量较低,一般是以副矿物的形式存在。
在岩浆结晶分异演化过程中,根据鲍文反应序列分为连续和不连续系列。
岩浆中先后结晶出橄榄石、辉石、角闪石等暗色矿物,斜长石伴随暗色矿物且牌号递减依次结晶出来,从基性向酸性斜长石演化。
Zr 在基性岩浆中不饱和,锆石难结晶出来,而在酸性岩浆中饱和可以晶出。
CL 阴极发光的原理实质上是由于矿物中可能会混入杂质离子或者是晶体生长过程中产生的缺陷、双晶、生长条纹等,这些因素都可能导致矿物颗粒内部由于成分不均一而在阴极发光图像上呈现不同,锆石环带很好的记录了岩浆演化的过程。
在对锆石的CL 阴极发光影像图中,不同岩石成因的锆石在CL 阴极发光图像下形态会有显著的区别。
岩浆锆石广泛存在于酸性岩浆岩中,而在偏基性的岩石中存在的较少,岩浆锆石具有特征的同心韵律环带,具有自形到半自形的长柱状特征。
在沉积岩中也会以少量碎屑锆石的形式存在,碎屑锆石磨圆较好。
在高级变质岩中,特别是在原岩富含锆石的高级变质岩中,锆石的结构往往较为复杂,构成由晶核和变质增生组成的复杂结构。
变质锆石指的是变质作用过程中形成的锆石,成因不同的锆石(深熔作用形成、变质流体结晶、变质重结晶等)甚至是不同变质相下形成的锆石在阴极发光图像上都具有不同的环带特征以及锆石形态,如图1。
2锆石包裹体包裹体是矿物生长过程中或形成之后被捕获包裹于矿物晶体缺陷中的,保存在主矿物至今的物质。
地质温度计
地质温度计地质温度计是能够用来确定地质作用温度的地质产物。
目前应用比较普遍的地质温度计主要有矿物包裹体地质温度计、同位素地质温度计、同质多象温度计、泥质矿物温度计、矿物分解温度、固溶体分解温度、矿物中的放射性裂变径迹、镜质组反射率、生物标志化合物等。
矿物包裹体根据矿物晶体中原生包裹体的均一化测定矿物的形成温度。
这种原生包裹体通常叫矿物温度计。
包裹体可以是固态的，矿物包裹体测温法的一种，在室温下从显微镜中看到的包裹体中的气相和液相，是单相热液随主矿物冷缩所产生的气泡。
如果用实验方法对包裹体加热到某一温度时，包裹体可恢复到形成时的均一相。
由于均一温度是在常压下得到的，因此需加压力校正值。
这时的温度就叫均一温度，这种测温的基本方法叫均一法。
常用于测定透明矿物，它是包裹体测温的基本方法。
测定不透明矿物的方法叫爆破法，是根据气液包裹体爆破产生的响声来确定温度的。
从包裹体爆破曲线图上可得出爆破温度，爆破温度经过压力校正之后可认为是矿物形成温度的上限同位素根据共生矿物对的同位素分馏（见稳定同位素地球化学）测定地质体中同位素平衡时的温度。
由同位素分馏作用已知，同位素交换反应的分馏系数（α）随温度（T）而变化，它们之间的关系式为1000lnα=(A/T)+B该式为同位素地质温度计的计算公式，A和B是实验确定的常数，与矿物种类有关。
目前常用的有石英－磁铁矿、石英-白云母、石英-方解石等共生矿物对氧同位素地质温度计和闪锌矿-方铅矿、黄铁矿-方铅矿等硫同位素地质温度计。
同位素地质温度计不需进行压力校正。
闪锌矿闪锌矿中常含有一些微量元素，如铟(In)、锗(Ge)、镓(Ga)、铊(Tl)等，这些微量元素含量的多少常与闪锌矿的形成温度有关（见表）。
因此,闪锌矿地质温度计又称矿物－微量元素地质温度计或类质同象地质温度计。
闪锌矿（ZnS）主要产于接触交待矽卡岩和中低温热液矿床中，若其形成温度较高，则含铁质较多，它的颜色容易呈现黑色或褐黑色；如其形成温度不高，则含铁质较少，因而呈现较浅的黄色、褐黄色。
三元长石地质温度计及其在我国粤西花岗岩中的应用
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2020-2021化学二模试题分类汇编——科普阅读题综合含答案解析
一、中考初中化学科普阅读题1．碳酸钠是一种重要的化工原料。
吕布兰、索尔维和侯德榜为碳酸钠的工业化生产做出了巨大贡献。
I、吕布兰法1789年，法国医生吕布兰（N．Leblanc，1742-1806）以食盐、浓硫酸、木炭和石灰石为原料，开创了规模化工业制取碳酸钠的先河，具体流程如图：（1）碳酸钠俗称__________。
（2）不断有科学家对吕布兰法进行改进，是因为此法有明显不足，请写出一条不足之处__________________________________。
Ⅱ、索尔维法1892年，比利时工程师索尔维发明氨碱法制碳酸钠，又称索尔维法。
原理如下：NaCl+NH3+CO2+H2O═NaHCO3↓+NH4Cl 2NaHCO3ΔNa2CO3+CO2↑+H2O。
某兴趣小组采用下列装置模拟索尔维法制备碳酸氢钠，进而制得碳酸钠，实验完毕后，将三颈烧瓶内的反应混合物过滤、洗涤、低温干燥，并将所得固体置于敞口容器中加热，记录剩余固体质量，实验记录如下：加热时间/min t0t1t2t3t4t5剩余固体质量/g未记录15.313.711.910.610.6请回答下列问题：（3）装置图中，饱和NaHCO 3溶液的作用是________（用化学方程式表达）（4）有同学认为应该在长颈漏斗内放置一团蘸有酸液的棉花，理由是______（5）根据实验记录，计算t 2时NaHCO 3固体的分解率是________（已分解的NaHCO 3质量与加热前原NaHCO 3质量的比值）（精确到0.1%）。
若加热前NaHCO 3固体中还存在少量NaCl ，上述计算结果将________（填“偏大”、“偏小或“无影响”）。
（6）制碱技术在很长一段时间内把持在英、法等西方国家手中，我国化学工程专家侯德榜先生独立摸索出索尔维法并公布与众，又于1943年创造性地将制碱与制氨两种工艺联合起来，基本消除废弃物的排放，同时生产出碳酸钠和氯化铵两种产品，这就是著名的侯氏制碱法。
微量元素在地质中的运用
微量元素在地质上的应用微量元素在地质上的应用主要有以下几个方面：一、分配系数的应用1. 计算平衡时的温度由热力学可知：\nk=-BRTK:平衡常数，在稀溶液条件下，K=D△日二热熔变化，可以测定，R二气体常数，B为常数，据此可求得温度: AIn D BT这就是微量元素的分配系数温度计。
很多温度计已经测定，特别是稀土元素和硫化物对。
2. 计算平衡时的压力根据热力学，在恒温条件下，分配系数D与压力P的尖系式为：lln D ' ・v 5P j ” RT3. 判断岩浆成岩过程⑴模型A部分熔融模型a. 平衡部分熔融C,= 1Co_D（1 _F）F其C L :兀素在熔体中的浓度；中：Co：初始固相母体物质中的浓度F:部分熔融特度D :总分配体系b：分离熔融模型（在发生熔融时，从固相中连续移出所形成的熔体「丄（1卫）PCo D D P ：压力c.结晶作用模型分离结晶作用过程中，微量元素的行为可用下式来描述：CL 二D'4砂F CL： i元素在熔体中的浓度；C O,L： i元素在原始熔体中浓度;F :原始岩浆分离结晶作用后剩余的份额（固结度，结晶度），还有其它模型。
（2）过程鉴别（3）地球化学参数的确定①源区的物质成分根据地质观察，综合考虑岩石学、微量元素、残留体和同位素组成等资料。
e.g.基性岩和超基性岩取上地幔为源区物质，以2倍左右球粒陨石的丰度为C。
值；花岗岩：S型花岗岩以杂砂岩的平均成分为G, I型花岗岩源岩为下地壳和上地幔物质的混合，有人以岩体边缘相为G。
二微量元素指示剂1 •对岩浆演化过程的指示（1）大离子半径亲石兀素大禺子亲石兀素一般有：Ba ・ RbSr、K 等。
丿元糸价态半径⑺Sr+2 1.12Ca+2 1.00Rb+ 1 1.47K+ 1 1.33Ba+2 1.34①S心和Sr在钙长石一熔体中的分配系数较大（即S®易进入含矿物中），在中酸性岩浆演化过程中，Sr随Ca的减少而贫化，但S®的半径比Ca?+大，C*比Sr2+B先进入晶格，随岩浆作用的进行，Sr/Ca比值变大，若以同源不同阶段岩石中的Sr和Ca作图，可得到演化线。
成矿物质来源及其研究方法-矿床学
第十一章成矿物质来源及其研究方法第一节成矿物质来源与含矿建造现代矿床学研究表明，多数矿床，尤其是非成岩矿产矿床都具有成矿物质多来源的特征，重视成矿物质多来源是矿床学地球化学的研究趋势。
同时研究发现，许多矿床成矿作用具有复合成矿的特点，常不是一次成矿作用完成的，而是经过了预富集到再富集成矿的多次地质作用完成的。
我们把预富集阶段形成的成矿物质丰度较高的岩石组合称为含矿建造，含矿建造是包含一系列含矿岩石与非含矿岩石的岩石系列，包括沉积岩、变质岩和岩浆岩。
含矿建造中有一部分是成矿元素的富集岩，一部分是具有与矿化有关的矿化剂元素，如S、Cl、F、C等。
而根据矿床学研究成矿物质来源分为直接来源与间接来源。
直接由地幔岩浆、花岗岩浆或沉积介质提供成矿物质到矿床中的物质来源称为直接来源，由幔源、壳源固结岩石，即矿源层或矿源岩提供成矿物质所反映出的幔源或壳源来源特征，称为间接物质来源。
对于成岩矿产成矿物质来源可能更多地反映直接物质来源，而对于非成岩矿产，由于其经过多次富集成矿，其物质来源特征可能更多反映间接物质来源。
一、上地幔物源含矿建造以上地幔为直接成矿物质来源的矿床局限于有限的矿床类型：1、与镁铁质、超镁铁质岩和部分碱性岩浆有关的矿床，在空间、时间和成因上与岩浆岩有联系，矿产种类有钒钛磁铁矿、铬铁矿、铜镍硫化物、钛铁矿－金红石－磷灰石、金刚石、铌、稀土等，大部分是成岩矿产。
部分形成上地幔岩含矿建造，其中富集Ni、Co、Ag、Bi、U等。
2、与镁铁质火山有关的矿床，主要形成于火山期后热液自变质交代作用或喷流喷气作用。
其中包括块状硫化物、玢岩铁矿、黑矿型矿床等。
3、与上地幔煌斑岩岩浆有关的绿岩型金矿，可以通过地幔对流煌斑岩侵位形成金矿；富金煌斑岩浆在地壳浅层与地壳物质发生反应形成花岗岩浆或加入变质热液中参与成矿。
煌斑岩脉含金丰度一般87PPb，明显高于壳源岩，金一般以Au－F络合物搬运。
以上地幔岩为物源岩含矿建造，成矿物质间接来自地幔，这类矿床对于前寒武纪变质岩区金矿最为重要。
地球科学中火成岩矿物温压计研究进展
地球科学中火成岩矿物温压计研究进展发表时间：2020-08-18T17:09:01.257Z 来源：《中国西部科技》2020年第8期作者：冉亚洲[导读] 火成岩结晶的温度、压力对于研究火成岩形成时的岩浆结晶环境、熔体演化过程具有重要意义。
摘要：火成岩结晶的温度、压力对于研究火成岩形成时的岩浆结晶环境、熔体演化过程具有重要意义。
岩浆结晶过程中某些元素在成岩矿物中的含量与岩浆结晶的温度、压力有很好的相关性，通过矿物压力计获得岩浆结晶时的压力，可以计算出岩浆侵位冷凝结晶时的深度。
通过矿物温度计获得岩浆冷凝结晶时的温度，根据地温梯度推演结晶深度，并能进一步验证通过压力计获得的成岩深度的准确性。
研究者通过低温热年代学手段获得岩浆剥露到地表的时间，结合岩浆侵位结晶的年龄、侵位的深度，可以获得岩浆隆升剥蚀的速率。
对比区域不同花岗岩隆升剥蚀过程，解释造山带演化过程。
本文综述了矿物温度压力计的研究进展，包括角闪石-斜长石温度压力计、绿帘石温度计。
关键词：矿物温度计、矿物压力计、岩体隆升1角闪石、斜长石矿物温度压力计1.1角闪石全铝压力计Hammarstrom and Zen（1986）通过电子探针分析高压和低压钙碱性侵入体中角闪石AlT和Alⅳ之间的线性拟合关系：Alⅳ=0.15+0.69 AlT，r2=0.97，而角闪石中的AlT含量又与角闪石结晶时的压力和温度有很好的对应关系，即角闪石的全铝含量随着压力升高而增大。
所以角闪石便成为探究火成岩结晶温压条件的可靠矿物（Bluandy and Holland , 1990），而角闪石全铝压力计对于角闪石的种类又有要求，通常闪长岩类岩石中的普通角闪石、浅闪石、韭闪石、钙镁闪石比较适用。
研究中通过对比前人文章中火成岩侵入体和自然岩石的矿物相平衡实验得到在特定矿物组合（斜长石、角闪石、黑云母、钾长石、石英、榍石、磁铁矿或钛铁矿±绿帘石）下，角闪石全铝压力计的计算公式。
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第23卷 第4期2004年12月 岩 石 矿 物 学 杂 志ACTA PETROLO GICA ET MIN ERALO GICAVol.23,No.4 Dec.,2004文章编号:1000-6524(2004)04032710二长石地质温度计在估算乌拉山金矿碱性长石形成温度中的应用胡 萍1(1.中国地质大学,湖北武汉 430074;2.摘 要:种类的脉状地质体。
含金矿脉中主要矿物共生组合为碱性长石金属硫化物。
矿床的显著特征为碱性长石交代作用强烈文采用电子显微探针分析了共生碱性长石和斜长石的化学成分,并采用三元二长石温度模型估计了碱性长石的平衡温度。
结果表明,第一成矿阶段的碱性长石石英含金矿脉中碱性长石的形成温度为353℃,第二成矿阶段石英含金矿脉中碱性长石的形成温度为281℃,矿脉碱性长石形成压力约为5kbar。
这些结果与同类矿石中平衡共生的碳酸盐矿物和云母类矿物的地质温度计估计的形成温度以及共生石英中流体包裹体的均一温度非常一致。
因此,乌拉山金矿床形成和富集的温度可估测为260～380℃,压力约为5kbar。
此外,应用二长石温度计计算了本地区区域变质片麻岩和花岗岩中碱性长石的平衡温度,所得温度比采用共生铁铝榴石和黑云母温度计估计的温度要低约250℃。
这表明共生的铁铝榴石和黑云母的平衡温度可能代表其寄主变质岩变质期温度及寄主花岗岩原生温度,而区域变质岩和花岗岩中的碱性长石在经历了随后多次热液作用后,可能重新平衡再生,这也与前人对乌拉山金矿的矿床地质和同位素研究的结果一致。
关键词:碱性长石;形成温度;二长石温度计;乌拉山金矿床;内蒙古中图分类号:P578.968;P618.51 文献标识码:AFormation temperatures of alkali feldspars from the Wulashan gold deposit:an estimate by t wo-feldspar thermometryPing HU1,2,Linghu ZHAO1and Qiujuan B IAN1(1.China University of G eosciences,Wuhan430074,China;2.Northeastern Illinois University,Chicago,IL60625,USA)Abstract:The Wulashan gold deposit,Inner Mongolia,China,which is characterized by intensive alkali feldspar metasomatism,is hosted by the late Archean gneiss,amphibolite,migmatite,and marble of the Wu2 lashan Group and surrounded by several intrusions.The general mineral assemblage of mineralized lodes is alkali feldspar+quartz+plagioclase+carbonate(calcite and Fe-dolomite etc).Alkali feldspar is also present as a major component within country rocks.On the basis of the microprobe analyses for coexisting alkali feldspar and plagioclase,the equilibrium temperatures of the alkali feldspars are calculated using several ternary two-feldspar geothermometers.The obtained temperatures at5kbar are353℃for alkali feldspars from gold-bearing veins I (K-feldspar-quartz veins),and281℃for alkali feldspars from gold-bearing veinsⅡ(quartz veins),in good a2 greement with the estimated temperatures for coexisting carbonates,mica minerals and gold,and with the ho2 mogeneous temperatures of fluid inclusions in quartz and alkali feldspars.Therefore,the gold mineralization in收稿日期:20040421;修订日期:20040625基金项目:教育部科学技术研究基金资助项目(9549115)作者简介:胡 萍(1970),女,汉族,博士研究生,研究方向为矿物学。
the Wulashan gold deposit formed at the temperatures ranging from280～360℃and the pressure of5kbar.On the other hand,the temperatures of alkali feldspars from regional metamorphic gneiss and granite are lower than the equilibration temperatures of coexisting almandine and biotite,indicating that the temperatures of almandine and biotite may represent the peak temperature of metamorphism and alkali feldspars in metamorphic rocks and granite may re-equilibrate after experiencing numerous overprinting thermal/magmatic events.K ey w ords:alkali feldspar;formation temperature;two-feldspar thermometer;the Wulashan gold deposit;In2 ner Mongolia1 IntroductionThe chemical compositions of alkali feldspar are dependent on temperature,pressure,oxygen fugaci2 ty,fluid compositions,coexisting mineral associa2 tions,and bulk-rock composition.Therefore,some features of alkali feldspars could be useful indicators of the physicochemical environment in which it grew. Barth(1951)presented an empirical two-feldspar thermometer using measurements of the distribution of NaAlSi3O8(Ab)between naturally occurring plagio2 clases and alkali feldspars.Several other two-feldspar thermometers have been calibrated considering the ef2 fect of pressure(Stormer,1975;Powell&Powell, 1977;Whitney&Stormer,1977;Heselton et al., 1983).However,these models do not include the conditions for equilibrium provided by KAlSi3O8(Or) and CaAl2Si2O8(An),and do not consider Al-Si or2 dering.The equilibrium of all three components in co2 existing feldspars,as well as Al-Si ordering,should be taken into account in thermodynamic models of feldspar equilibrium(Parsons&Brown,1983). Thus,more recently,the thermodynamic formula2 tions of feldspar activity-composition relations include constraints from equilibrium among the Ab,Or and An components in coexisting alkali feldspars and pla2 gioclases(Ghiorso,1984;Green&Udansky,1986; Fuhrman&Lindsley,1988;Lindsley&Nekvasil, 1989;Elkins&Grove,1990;Kroll et al.,1993).One unique feature of the Wulashan gold deposit is the intensive alkali feldspar metasomatism.This “potassic wash”is associated with silicification that lo2 cally extends for several meters into the host rocks (Hart et al.,2002).Field studies showed that alkali feldspar metasomatism is closely associated with the evolution of gold mineralization in both space and time.Fluid inclusion and stable isotope studies of gold-bearing quartz veins have been carried out and several competing ore genesis models were therefore proposed(Hart et al.,2002).Alkali feldspars widely exist in all varieties of rock types in this area,but the mineralogy of alkali feldspars in this area has not been studied in details so far.In this paper,the chemical compositions of coexisting alkali feldspars and plagio2 clases from the Wulashan gold deposit are analyzed us2 ing electron microprobe.The formation temperatures of alkali feldspars are estimated and compared using several ternary two-feldspar thermometers.The for2 mation temperatures and pressure of alkali feldspars are further applied to reveal the characterization of the Wulashan gold deposit,and to provide constraints on the conditions of gold mineralization in the Wulashan gold deposit.2 G eological settingThe Wulashan gold deposit is situated along the northwestern margin of the North China craton,and on the northern side of the Daqingshan-Wulashan fault belt(Zhang et al.,1999).The major host rocks are the Archean high-grade metamorphic volcano-sedi2 mentary rocks of the Wulashan Group,e.g.,banded amphibolite,garnet-biotite-plagioclase gneiss,horn2 blende-plagioclase gneiss,sillimanite-biotite gneiss, and magnetite-plagioclase-hypersthene-pyroxene gran2 ulite(G an et al.,1994).The Late Paleozoic Dahuabei granitoid batholite is the major intrusion in this area,which intruded the Archean Wulashan Group and is about4kilometers west to the Wulashan823 岩 石 矿 物 学 杂 志 第23卷gold deposit(Nie&Bj rlykke,1994).In addition, there are also a number of granitoid stocks,pegmatite dikes,migmatite veins,K-feldspar alteration and magmatic hydrothermal veins in this area(Nie et al., 2002).The gold mineralization occurs in quartz-K feldspar veins(gold-bearing veinsⅠ)and quartz veins (gold-bearing veinsⅡ)with small amount of base metal sulfides, e.g.,pyrite,chalcopyrite and gale2 na.Alteration throughout the mineralized region is dominated by extensive alkali feldspar flooding adja2 cent to veins,dikes,faults,and breccias.The miner2 alization veins are200-500m(up to1000m)long along E-W or close to E-W,1-3m(up to10m) wide,and250-400m deep,and are spatially associ2 ated with the intrusive stocks,dikes and veins(Hart et al.,2002).3 Samples and analytical methodsCoexisting alkali feldspar(AF)and plagioclase feldspar(PF)samples were collected from all rock types exposed in the Wulashan gold deposit:(1) gneisses(e.g.,biotite-plagioclase gneiss,biotite-muscovite-plagioclase gneiss,mucscovite-plagioclase gneiss and feldspar-quartz gneiss),(2)migmatite, (3)granite,(4)altered granite,(5)pegmatite,(6) magmatic hydrothermal veins,(7)gold-bearing K feldspar-quartz veins,and(8)gold-bearing quartz veins.The chemical compositions of AF and PF were analyzed using J EOL model733electron microprobe operating at15kV and10nA.On-line data reduction and the matrix correction procedure of Bence and Al2 bee(1968)were employed.An alkali feldspar sample of known compositions was employed for standardiza2 tion.Counting times were optimized to provide the lowest possible counting-statistical errors,while mini2 mizing electron beam damage to the samples.For ex2 ample,the counting time of20seconds for Na as the first element in each analysis was used to produce ac2 ceptable counting-statistic errors and to result in no measurable loss in Na X-ray intensity during analysis. The analytical uncertainties based on counting statis2tics are estimated on the level of～2%of the amount present for major elements.3.1 T ernary t w o-feldspar thermometerAt equilibrium the chemical potentials of Ab,Or and An in coexisting AF and PF are equal. μPF Ab=μAF Ab(1) μPF An=μAF An(2) μPF Or=μAF Or(3) For each phase the equilibrium conditions may be ex2 pressed in terms of a standard state free energy term for each component and a free energy of mixing. μPF Ab=μ0PFAb+R T lna PF Ab(4) μAF Ab=μ0PFAb+R T lna AF Ab(5) Coexisting AF and PF are assumed to be part of a con2 tinuous solution,with the same standard state free en2 ergies for each component.Therefore,the activities of Ab,Or and An in coexisting AF and PF are equal. a PF Ab=a AF Ab(6) a PF An=a AF An(7) a PF Or=a AF Or(8)The excess free energy of mixing for ternary feldspar is expressed using a ternary Margules parame2 ter that includes asymmetric terms for each binary and ternary interaction term.The algebra formulations for the activities of Ab,Or and An in coexisting AF and PF are developed using the excess free energy of mix2 ing and the mole fraction of Ab,Or and An.The ex2 cess terms for ternary feldspar are defined based on the fitting to experimental data(Seck,1971;Johannes, 1979)and given by Ghiorso(1984),Green&Udan2 sky(1986),Fuhrman&Lindsley(1988),Lindsley &Nekvasil(1989)and Elkins&Grove(1990). Thus,three temperatures(T Ab,T Or and T An)can be calculated at a given pressure,each one expressing the equilibrium temperature based on the activity of that component.Ideally,for two feldspars at equilibrium, these temperatures should all be the same;in reality they rarely are,because of(1)analytical uncertainty in determining exact feldspar compositions,(2)diffi2 culties in estimating amount of exsolution and re-equilibrium that occurred after crystallization of each feldspar,(3)uncertainties in the estimation of pres2923 第4期 胡 萍等:二长石地质温度计在估算乌拉山金矿碱性长石形成温度中的应用 sure,and(4)errors associated with the model.A SOLVCALC program package was developed for calculating the ternary feldspar solvus and for ternary two-feldspar thermometer(Wen&Nekvasil, 1994),in which the popular models of Ghiorso (1984),Green&Udansky(1986),Nekvasil& Burnham(1987),Fuhrman&Lindsley(1988), Lindsley&Nekvasil(1989)and Elkins&Grove (1990)are included.At a given pressure and a two-feldspar compositional pair,the program searches for the closest matching tie-line and calculates the equilib2 rium temperature by adjusting the compositions within an uncertainty as defined.The program was designed to calculate the temperature from400℃to1300℃at the pressure range of1bar to15.0kbar.However,it has been used to calculate and give reasonable temper2 ature data down to300℃(Jenkin et al.,2001).The SOLVCALC program was applied in this work to estimate the equilibrium temperature of coex2 isting AF and PF within an uncertainty of2%adjust2 ed for each component in each phase.In order to test the effectiveness of this program,the end-member compositions of several coexisting AF and PF from metamorphic and volcanic rocks(Elkins&Grove, 1990)were cited to calculate the equilibrium tempera2 tures using Fuhrman&Lindsley(1988)(F&L)and Elkins&Grove(1990)(E&G)models.The results are summarized in Table1,in which the temperatures calculated by Fuhrman&Lindsley(1988)and Elkins &Grove(1990)are also given for comparison.Three estimated temperatures(T Ab,T Or and T An)using the SOLVCALC program are reasonably close within ～50℃for each coexisting AF and PF pair,and are in good agreement with the data reported by Fuhrman& Lindsley(1988)and Elkins&Grove(1990).T able1 Comparison of temperature calculated using different tw o-feldspar modelsMetamorphic rocks Volcanic rocksBM-15IN-11MM-2SR-311234 End-member compositionsAF Or0.7510.6390.7000.6380.6030.6530.6300.650 Ab0.2350.3480.2560.3140.3790.3190.3620.337 An0.0140.0060.0360.0310.0180.0280.0080.013PF Or0.0140.0170.0300.0100.0730.0410.0610.076 Ab0.7430.7850.7620.7130.6540.6320.7980.702 An0.2420.1930.2050.2730.2730.3260.1410.222Fuhrman&Lindsley(1988)and Elkins&Grove(1990)Pressure(kbar)88881111F&L T Ab/℃707764723763849807676770 T Or/℃612604665598821756676772 T An/℃708750725766832776671779E&G T Ab/℃698763728786868813687769 T Or/℃618615680616863782679770 T An/℃685746807720862796680770This studyPressure(kbar)88881111F&L model T Ab/℃708769733801849808676789 T Or/℃618632678624821761676797 T An/℃707744748798832774671790E&G model T Ab/℃702758734796866812680767 T Or/℃605618672621860785674767 T An/℃676752816757861793677769033 岩 石 矿 物 学 杂 志 第23卷3.2 The end-m ember compositions of alk ali feldsp arThe chemical formulae of AF and PF are calculat2 ed based on the electron microprobe data and8oxygen atoms per molecule.The normalized end-member compositions of representative coexisting AF and PF from the Wulashan gold deposit are given in Table2, and projected in the ternary triangle diagram of feldspar(Fig.1),where the dash lines connected some coexisting AF and PF pairs.It can be seen that the contents of Or in PF and of An in AF are very low.The PFs are albite and oligoclase.The contents of Or in most alkali feldspars are in the range of88-99%,with the exception of one sample from migmatites(Or=62%).T able2 The end-member composition of representative co-existing alkali feldspars and plagioclases fromthe Wulashan gold depositSample#Alkali feldspar(mol%)Plagioclase feldspar(mol%)Or Ab An Or Ab AnRegional metamorphicgneisses 3090.8870.1020.0110.0130.7130.278 3120.9150.0750.0100.0170.6890.294Migmatite 901-30.6210.3770.0020.0110.6920.297 919-30.9550.0450.0010.0030.9850.012 917-20.8950.0970.0080.0010.9980.001Granite 9A-10.6930.3050.0020.0070.9870.006 3060.8760.1170.0070.0380.8260.136 3380.8860.1070.0070.0010.9980.001Altered granite 3111-20.8960.1020.0020.0050.9380.057 3260.9530.0410.0060.0210.9690.010 3420.9240.0760.0010.0100.8750.115Pegmatite 3660.9360.0640.0010.0060.9830.011 3820.9580.0420.0010.0160.9770.007MHV4151-30.9470.0530.0010.0020.9820.016G old-bearing veinⅠ354-10.9240.0710.0050.0050.8960.099 3170.9500.0410.0090.0050.8290.166 CM1390.9670.0330.0010.0050.8960.099 3370.9630.0370.0010.0050.8090.186 3310.9530.0470.0010.0050.8910.105 41530.9500.0500.0010.0050.9060.089G old-bearing veinⅡCM1810.9910.0070.0020.0050.8400.155 3340.9720.0270.0010.0050.8940.102 3360.9630.0250.0120.0050.8920.103 3670.9700.0240.0060.0050.9160.079 MHV—Magmatic hydrothermal veins.3.3 T emperatures from different modelsThe normalized end-member compositions are in2 put into the SOLVCALC program and adjusted within a defined uncertainty of2mol%.The three tempera2 tures(T Ab,T Or and T An)of coexisting AF and PF from the Wulashan gold deposit are estimated at the pressure of1,5,and8kbar using four ternary two-feldspar thermometer models(Green&Udansky, 1986;Fuhrman&Lindsley,1988;Lindsley&Nek2 vasil,1989;Elkins&Grove,1990).T Or and T An are generally variable in a greater range,even for the same thermometer model,indicating that T Or and T An may be not reliable,probably due to the low con2 tents of Or in PF and of An in AF.The T Ab data of representative alkali feldspars are given in Table 3. The T Ab of alkali feldspars estimated at8kbar are shown in Fig.2.The T Ab of alkali feldspars estimated using Fuhrman&Lindsley(1988),Lindsley&Nek2 vasil(1989)and Elkins&Grove(1990)models are quite consistent and are well within±50℃.The er2 ror of±50℃is an acceptable error for any meaningful two-feldspar thermometer,considering the analytical133 第4期 胡 萍等:二长石地质温度计在估算乌拉山金矿碱性长石形成温度中的应用 Fig.1 Compositions of coexisting alkali feldspars (AF )and plagioclase feldspars (PF )in the ternary triangle diagramuncertainty of exact compositions ,uncertainty of esti 2mated pressure ,the possible exsolution or re-equilibri 2um after the crystallization of feldspars ,and the possi 2ble errors of the model pared with the T Ab from the other models ,the T Ab of alkali feldspars esti 2mated from Green &Udansky (1986)appears too high at higher temperatures ,but too low at lower temperatures ,and changed within the range of ±150℃.Although none is taken as a prior ,Fuhrman&Lindsley (1988),Lindsley &Nekvasil (1989)and Elkins &Grove (1990)models appeared to give more consistent and reasonable temperature estimates for al 2kali feldspars from the Wulashan gold deposit.TheT Ab data of alkali feldspars from Elkins &Grove(1990)model will be further discussed.T able 3 Form ation temperature (T Ab /℃)of alkali feldspar estim ated using different tw o -feldspar geothermometer modelsSample #Pressure (kbar )E &G model L &N modelF &L modelG &U model15810888Barte (1961)Regional metamorphicrocks 309434479549555507527538510312405461503524471492458464Migmatite901-3781815846904854912978995919-3292341378403378368248360917-2310357393416407387413447Granite9A-1477524563577567516600709306429487525549499514498508338324372408432417403397462Altered granite3111-2391443483509482476401464326254301337360336325311353342372475465491451457396432Pegmatite 366326377415440353405329396382288337373398373363304355MHV4151-3308357395420330385362376G old-bearing vein Ⅰ354-1325376414439411406403420317287336373398365365340372CM1392843333703943673602933453373133654014263893923233653313163664044294003953373794153318368406431404397299383G old-bearing vein ⅡCM181219264298320290289174253334270318354378351345274329336237283317340314308331323367215260293315290283264319MHV —Magmatic hydrothermal veins ;E &G —Elkins &Grove (1990);L &N —Lindsley &Nekvasil (1989);F &L —Fuhrman &Lindsley (1988);G &U —Green &Udansky (1986)。