Advances in Research of Mineral Chemistry of Magmatic and Hydrothermal Biotites

Biotite is an important hydrated ferromagnesian silicate mineral in igneous rocks and porphyry deposits.The determination of chemical compositions of biotite plays an important role in both igneous petrology and ore forming processes.This paper summarizes research results of magmatic and hydrothermal biotites exemplified by the Lakange porphyry Cu–Mo deposit and the Qulong porphyry Cu deposit in the Gangdese porphyry–skarn metallogenic belt,Tibet.Biotite mineral chemistry can provide critical insights into classification,geothermometer,geothermobarometry,oxygen fugacity,petrogenesis and tectonic setting,evaluating magmatic-hydrothermal process by halogen and halogen fugacity ratios,and distinguishing between barren and mineralized rocks.Biotite provides the latest mineralogical evidence on metallogenic prognosis and prospecting evaluation for porphyry Cu polymetallic deposits or magmatic hydrothermal deposits.

^(40)Ar/^(39)Ar ISOTOPIC DATING THE BIOTITES FROM THE IGNEOUS AND METAMORPHIC ROCKS OF THE ZHONGSHAN STATION AREA

The Zhongshan Station of China is located in the Larsemann Hills, East Antarctica. Low pressure granulite facies gneisses together with late granites are outcroped in the region. Three biotite samples from a garnet segregation, a syenogranite and a granite-pegmetite were measured with 40Ar/39Ar incremental heating technique. Biotites from the garnet segregation give an 40Ar/39Ar plateau age of 504±1Ma. Biotites from the syenogranite yield an 40Ar/39Ar plateau age of 494 ±1 Ma. Biotites from the granite-pegmatite give an 40 Ar/39 Ar plateay age of 486±1Ma. They verify 500 Ma thermal event called 'Pan African event' by previous K-Ar and Rb-Sr data. They are cooling ages of the biotites when the paleogeotherm of the area droped to the K-Ar closure temperature for biotite.

Late Triassic Biotite Monzogranite from the Western Litang Area,Yidun Terrane,SW China: Petrogenesis and Tectonic Implications

The Late Triassic igneous rocks in the Yidun terrane can provide vital insights into the evolution of Plaeo-Tethys in western China. We present new zircon U-Pb, whole-rock geochemistry, and Sr-Nd-Pb-Hf isotopic data for the Litang biotite monzogranites, Yidun terrane. The biotite monzogranites have a zircon U-Pb age of 206.1±1.0 Ma(MSWD=1.9,n=30), which indicates Late Triassic magmatism. The biotite monzogranites display I-type affinity, high Na_2O(3.38-3.60 wt%) contente,medii SiO_2(67.12-69.13 wt%), and low P_2 O_5 contents(0.10～0.12 wt%). They enriched in Rb,and Ba and depleted in Nb and Ta, with negative Eu anomalies(Eu/Eu*=0.74—0.81). They have evolved Sr-Nd-Pb-Hf isotopic composition, i.e.,(^(87) Sr/^(86 )Sr)i=0.714225 to 0.714763, negative ?_(Nd(t)) values of -2.0 to-2.6 with two-stage Nd model ages ranging from 1.01 to 1.05 Ga, negative ?_(Ht)(t)) values o f-3.4 to-4.1 with two-stage Hf model ages of 1.85 to1.88 Ga, suggesting a matured crustal sources. Their low Al_2O_3/TiO_2 ratios and medium Cao/Na_2O ratios, medium Mg~# and SiO_2 contents, low [molar Al_2O_3/(MgO+FeO^T)] values, and high [molar Cao/(MgO+FeO^T)] values indicate that the Litang biotite monzogranite was formed by partial melting of metabasaltic rocks. Based on the previous studies, we propose that the Litang biotite monzogranite derived from the westward subduction and closure of the Ganzi-Litang ocean during the Late Triassic-The mantle wedge-derived mafic melts provided sufficient heat for partial melting of ancient metabasalt protolith within the middle-lower crust.

A Report on a Biotite-Calcic Hornblende Geothermometer

This paper presents a biotite-calcic hornblende geothermometer which wasempirically calibrated based on the garnet-biotite geothermometer and thegarnet-plagioclase-hornblende-quartz geobarometer, in the ranges of 560-800 deg C (T) and 0.26-l.4GPa (P) using the data of metadolerite, amphibolite, metagabbro, and metapelite collected from theliterature. Biotite was treated as symmetric Fe-Mg-Al^VI-Ti quaternary solid solution, and calcichornblende was simplified as symmetric Fe-Mg binary solid solution. The resulting thermometer mayrebuild the input garnet-biotite temperatures well within an uncertainty of + - 50 deg C. Errors of+- 0.2 GPa for input pressure, along with analytical errors of = - 5 percent for the relevantmineral compositions, may lead to a random error of + - 16 deg C for this thermometer, so that thethermometer is almost independent of pressure estimates. The thermometer may clearly discriminatedifferent rocks of lower amphibolite, upper amphibolite and granulite facies on a high confidencelevel. It is assumed that there is a ferric iron content of 11.6 percent in biotite, and that theiron content in calcic hornblende may be calculated according to the method of Dale et al. (2000).This thermometer can be used for medium- to high-grade metabasites and metapelites.

Extraction of copper from copper-bearing biotite by ultrasonic-assisted leaching

Copper-bearing biotite is a refractory copper mineral found on the surface of the Zambian Copperbelt.Biotite is a copper oxide from which copper is extracted by various methods,especially by leaching.Leaching is the process of extracting a substance from a solid material dissolved in a liquid.To improve the efficiency of the leaching process by a more effective method,a new method called ultrasonic-assisted acid leaching is proposed and applied in this study.Compared with regular acid leaching,the ultrasound method reduced the leaching time from 120 to 40 min,and sulfuric acid concentration reduced from 0.5 to 0.3 mol·L^(-1).Besides,leaching temperature could be reduced from 75 to 45°C at the leaching rate of 78%.The mechanism analysis indicates that an ultrasonic wave can cause the delamination of a copper-bearing biotite and increase its specific surface area from 0.55 to 1.67 m^(2)·g^(-1).The results indicate that copper extraction from copper-bearing biotite by ultrasonic-assisted acid leaching is more effective than regular acid leaching.This study proposes a promising method for recycling valuable metals from phyllosilicate minerals.

花岗质岩石中黑云母成分区域性变化对深部物质示踪及成矿的约束:以秦岭地区为例

秦岭造山带早中生代花岗质岩浆及成矿作用非常发育,是探讨地壳深部物质组成及成矿关系的重要地区之一,学者已从岩石学、矿床学和地球化学等角度开展了众多研究,但对成矿作用与花岗岩和地壳深部物质组成的认识仍不太清楚。黑云母是中酸性岩中常见的暗色矿物,也是指示成矿可能性的重要矿物之一。因此,本文对秦岭该期花岗质岩石中黑云母成分开展研究,为解决该问题探索新途径。对秦岭早中生代花岗质岩石中黑云母成分的研究结果显示,北秦岭和南秦岭两个构造单元中黑云母成分和形成物理条件存在系统差异,揭示其岩浆物源有别,进而制约了其成矿种类特征。北秦岭早中生代花岗质岩石中黑云母的成分和形成条件变化范围小,以MgO(8%~13%)、TiO_(2)(3%~5%)和Cl(0.02%~0.6%)含量较高,F(0.2%~0.4%)含量较低,以及较高的氧逸度(log f O_(2)值为-16.96~-14.62)和温度(682~771℃)为特征;而南秦岭的成分和形成条件总体变化范围较大,具有MgO(3%~15%)、TiO_(2)(2%~4.5%)、Cl(0.01%~0.18%)含量较低,F(0.1%~1.6%)含量较高,以及较低的氧逸度(log f O_(2)值为-20.88~-15.08)和温度(536~754℃)。此外,研究还显示,黑云母的形成压力与岩浆演化程度和矿物组合相关,当岩石中出现黑云母+白云母±石榴子石组合时,压力较高。秦岭两个构造单元中黑云母成分和形成条件的差异,特别是氧逸度和Cl含量的明显不同,揭示各自的成矿种类和成矿潜力不同,如北秦岭较高的氧逸度和Cl含量,形成铜矿的潜力比南秦岭大。同时,两个构造单元中黑云母的成分差异,还揭示了岩浆物源及深部物质组成的不同,即北秦岭比南秦岭具有更为年轻的地壳,这与区域同位素填图示踪的深部物质组成差异基本一致。由此可见,对区域上同时代花岗质岩石中黑云母成分的研究,不仅可以揭示岩浆演化、岩浆结晶过程物理化学条件等,还可示踪深部物质组成的空间变化与差异及成矿种类和潜力,有望成为探测深部物质组成的新方法和了解区域成矿背景和潜力的新途径。

The Microarea Composition of Garnet and Biotite from the Ji'an Group in Tonghua District and Its Significance as an Indicator of Metamorphic P-T-t Path

The garnet (Grt) and biotite (Bt) from gneisses of the Ji’ an Group are characterized by diffusion zoning at the rim, but equilibrium composition of metamorphic peak is usually remained in extensive interior area. Garnet with growth zoning is also found in the kyanite zone.In the light of microarea compositional variation of Grt and Bt, the temperatuIe and pressuIe at the progressive, peak and post peak metamorphic stages are determined by correctly using GrtBt thermometer and GASP barometer. On this basis, a counterclockwise P-T-t path can be constructed, which reflects the closing process of an ensialic rift belt in this region during the Early Proterozoic.

Reviews in Garnet-Biotite Geothermometer: Its Versions, Inherent Problems of Accuracy and Precision, and Perspective for Further Research

This paper briefly introduces twenty one versions of garnet biotite Fe Mg exchange geothermometry, points out the sources of systematic errors inherent in geothermometry. The sources lie in that: (1) ideal Fe Mg mixing in garnet and biotite is assumed; (2) non ideal properties of both garnet and biotite are not considered completely; (3) minor elements—Mn, Ca in garnet, and Al Ⅵ, Ti, Mn in biotite are almost neglected; (4) effects of pressure on equilibrium, although little, are almost not taken into consideration, and experiments were conducted at one fixed pressure; (5) the data used for regression analysis is too scarce in quantity; (6) internal consistency of the data used for empirical calibration is not fully guaranteed; (7) the authors take energy parameters W’s (Margule’s parameters) independent of pressure and temperature, though the former are actually the functions of the latter items; and (8) the most important composition activity relationship is not consistent with the mineral compositions used for calibration. Furthermore, it is believed that empirical calibrations cannot avoid the following problems: (1) effect of retrograde metamorphism; (2) inconsistent data set; (3) effect of pressure on temperature estimation; and (4) effect of Fe 3+ calculation. Exact experimental work should be done in order to accurately calibrate the geothermometer in which the Margule’s parameters should be treated as the functions of pressure, temperature, and mineral compositions.

Hematite, Biotite and Cinnabar on the Face of the Turin Shroud: Microscopy and SEM-EDX Analysis

The Turin Shroud, recently accessible for hands-on scientific research, is now extensively investigated. Its pinkish red blood stains that seem anomalous ones are studied by modern techniques (notably by resolute optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray). Exploration by these techniques of a blood stain located on the face permits us to discover some red-colour particles (hematite, biotite and cinnabar) of exogenous material in this stain. We finally characterize these red-colour particles and try to explain their presences in the blood stain. Globally, all these red-colour particles cannot explain all of the reddish appearance of the area under study.

赣西北麦斜岩体岩石成因:来自黑云母矿物化学的约束

黑云母是花岗岩常见的暗色矿物之一。黑云母化学成分变化是寄主岩浆固结成岩时不同的物理化学条件下所对应的结果,因此,黑云母化学成分很好地记录了寄主岩浆的属性,对黑云母开展矿物化学成分的研究可以有效地反演寄主岩岩浆演化和成岩过程的物理化学条件,指示岩石的成因类型、岩浆物质来源等信息(Wones and Eugster,1965)。

赣西北麦斜黑云母花岗闪长岩中黑云母矿物化学特征及其对岩石成因的指示意义

黑云母是花岗岩中常见的暗色矿物之一,其化学成分可以有效反演寄主岩岩浆演化和成岩过程的物理化学条件、岩石成因类型及岩浆源区性质。本文利用电子探针对麦斜岩体黑云母花岗闪长岩中的黑云母进行了化学成分分析。结果显示,麦斜黑云母花岗闪长岩中黑云母以镁质黑云母和铁质黑云母为主,MgO含量为8.81%~10.69%,FeO^(T)含量为18.94%~21.27%,黑云母矿物化学成分特征指示麦斜黑云母花岗闪长岩属于I型花岗岩,并具有壳幔混合特征。黑云母结晶温度为492~645℃,平均595℃,岩浆氧逸度log(ƒ_(O_(2)))为-15.8~-13.7(≈ΔFMQ+0.1~ΔFMQ+0.2)。综合地质特征、矿物化学特征及前人岩石地球化学研究成果,认为幔源基性岩浆底侵作用提供热能,导致下地壳以岩浆岩为主的源区物质发生部分熔融,同时伴有少量幔源基性岩浆混入并直接参与了岩浆作用,进而形成麦斜黑云母花岗闪长岩。

北秦岭翠华山-库峪一带晚中生代花岗岩黑云母地球化学特征及成因

为探讨北秦岭造山带晚中生代岩浆复杂多样的成因机制,以北秦岭中段翠华山、大峪及库峪地区晚中生代二长花岗岩为研究对象,利用电子探针技术对其中的黑云母进行地球化学分析.结果显示,所采样品中的黑云母主体属于镁质黑云母,其成因类型为原生黑云母.矿物化学数据计算结果显示,翠华山、大峪及库峪二长花岗岩样品中黑云母的结晶压力均值分别为205、202、211 MPa,对应结晶深度分别为7.8、7.6、8.0 km,结晶温度均值分别为711、653、657℃,氧逸度均值分别为-16.45、-18.40、-18.27.基于上述结果分析,揭示研究区二长花岗岩主要物质来源于地壳并有少量幔源物质加入,翠华山、大峪及库峪二长花岗岩具有I型花岗岩亲缘性,均属于造山带钙碱性花岗岩系.

循环加卸载下黑云母石英片岩的弹性模量与能量演化特征研究

黑云母石英片岩是一种典型的各向异性岩石,为研究其损伤演化规律及各向异性表现特征,针对含0°,45°,90°3种片理角度的试样,开展了等塑性应变循环加卸载试验。结果表明:不同片理面角度试样的破坏模式有所不同,0°片理面试样中的张拉破裂现象与45°片理面中的剪切破坏现象尤为明显。随着塑性应变增加,黑云母石英片岩的弹性模量表现出先强化、后弱化的现象,这一现象在高围压下更为明显。在弱化阶段中,弹性模量演化的转折点与裂纹起裂强度σci稳定时对应塑性应变一致。弹性模量作为岩石损伤劣化过程的评价指标较完整性系数受片理面角度的影响更小。在岩石内部能量演化过程中,耗散能大小与片理面角度的关系为0°>90°>45°,耗散能、弹性能下降的速率大小关系为45°>90°>0°,其降至稳定时与岩石损伤强度σcd稳定时对应塑性应变一致。该研究借助弹性模量和能量演化规律分析,探究了黑云母石英片岩的损伤演化力学行为。

华北克拉通吉南夹皮沟新太古代石榴黑云斜长片麻岩的变质P-T-t演化及构造意义

华北克拉通东部陆块新太古代末期的构造体制是近年来备受学界关注的热点议题。本文对地处华北克拉通东部陆块东北部的吉南夹皮沟石榴黑云斜长片麻岩进行了详细的岩相学、矿物化学、变质相平衡模拟、传统地质温压计和锆石U-Pb年代学研究,以明确其变质P-T-t演化,探讨构造过程和动力学机制。石榴黑云斜长片麻岩主要由石榴石、黑云母、斜长石、角闪石、石英和少量钛铁矿组成,记录了逆时针P-T轨迹,可以划分为三个变质阶段。岩石第一阶段的矿物组合为黑云母+斜长石+角闪石+石英+钛铁矿(+熔体)(Bt 1+Pl 1+Amp 1+Qz+Ilm(+L)),记录的温压条件为790~854℃和0.55~0.88GPa,之后通过升压略降温到达压力峰期阶段,在这个过程中角闪石分解、石榴石生长、基质型斜长石的X_(An)值从核到边降低。第二阶段的矿物组合为石榴石+黑云母+斜长石+角闪石+石英+钛铁矿(+熔体)(Grt+Bt_(2)+Pl_(2)(核部)+Amp_(2)+Qz+Ilm(+L)),相平衡模拟获得该阶段的温压条件为670~745℃和1.10~1.24GPa,传统地质温压计的结果为707~771℃和0.99~1.18GPa,两者可相互佐证,可能代表了岩石的压力峰期阶段。第三阶段的矿物组合为黑云母+斜长石+石英+钛铁矿(Bt_(3)+Pl_(2)(边部)+Qz+Ilm),形成于压力峰期后的降温降压过程,石榴石边部分解形成斜长石,该类斜长石的X_(An)值从核到边逐渐升高。变质锆石U-Pb定年获得2483±8Ma(MSWD=3.2)的年龄,结合稀土配分模式和锆石Ti温度计计算结果,将该年龄解释为岩石压力峰期阶段前的变质时代。考虑到吉南变质地体新太古代末期岩浆活动与变质作用的时间重叠性、区域上的“穹窿-龙骨”构造样式、前人的变质作用资料以及石榴黑云斜长片麻岩记录的升压轨迹,本文认为吉南新太古代末期变质作用与重力凹沉构造有关。

西昆仑大红柳滩花岗岩中黑云母地球化学特征及地质意义

西昆仑大红柳滩岩体被认为与伟晶岩锂(铍)矿化密切相关。为约束大红柳滩岩体形成时的物理化学条件、岩石成因类型及源区性质,本文选取大红柳滩岩体作为研究对象,对花岗岩中的黑云母进行背散射观察(BSE)和电子探针分析(EPMA)。研究结果表明:大红柳滩二云母花岗岩与正长花岗岩中的黑云母属铁质黑云母,具有富硅、铝、铁和钾,贫镁、锰、钠和钙的特征;黑云母花岗岩中黑云母为铁质黑云母和镁质黑云母,具有富镁,贫铝、铁的特征。二云母花岗岩和正长花岗岩中黑云母具有高的AlⅥ值(0.7~0.9),与电气石、石榴子石和白云母等过铝质矿物共存。黑云母花岗岩中的黑云母具有高的MgO含量(9.30%~10.11%),黑云母与角闪石共存。通过黑云母成分估算二云母花岗岩、正长花岗岩及黑云母花岗岩中黑云母结晶温度分别为661℃~673℃、621℃~669℃、685℃~714℃,固结压力分别为332~404 MPa、356~377 MPa、248~270 MPa,对应侵位深度分别为12.46~14.98 km、13.18~14.38 km、9.18~10.01 km,氧逸度分别为-15.8~-15.0、-16~-15、-14.9~-14.0。综合研究结果表明,大红柳滩地区二云母花岗岩与正长花岗岩为壳源物质重熔的产物,具有典型强过铝质S型花岗岩的特点,而黑云母花岗岩是具有幔源物质混入成因的I型花岗岩。本研究成果为大红柳滩岩体不同岩性花岗岩成岩时的物理化学条件、岩石成因类型以及源区性质等方面提供了新资料。

花岗岩中黑云母地球化学特征对铟矿化的启示:以栾川矿集区鱼库‒石宝沟岩体为例

传统观点认为,铟常在锡多金属矿床中富集。但近年来发现,一些与花岗岩有关的贫锡多金属矿床中,铟也能够富集到一定程度。不可否认的是,无论在贫锡还是富锡的矿床中,铟的富集均与花岗质岩浆活动密切相关。然而,目前对于岩浆演化过程中控制In超常富集的因素尚不清楚。在花岗岩中,黑云母是Sn和In的重要载体矿物,其化学成分也可以有效反映岩浆成因及成岩物理化学条件。栾川矿集区的赤土店矿床为贫锡富铟的岩浆热液铅锌银矿床,其矿化与燕山期鱼库-石宝沟花岗岩关系密切。本文以鱼库-石宝沟花岗岩作为贫锡花岗岩的代表,对岩体中的黑云母开展了详细的矿物地球化学研究,并与华南典型锡铟矿化花岗岩中的黑云母进行对比。结果表明,鱼库-石宝沟花岗岩中的黑云母为镁质黑云母,华南锡铟矿化花岗岩中的黑云母为铁质黑云母-铁叶云母。且鱼库-石宝沟花岗岩中的黑云母具有较低的Sn、In含量,指示该花岗质岩浆贫锡和铟,而华南锡铟矿化花岗岩岩浆源区本身就富锡和铟。与鱼库-石宝沟花岗岩相比,华南锡铟矿化花岗岩起源于变沉积岩的部分熔融,且具有高温、低氧逸度、高挥发分的特征,这些物理化学条件对铟矿化有重要控制作用。而贫锡铟的鱼库-石宝沟花岗岩并不具备这些有利于铟矿化的条件,与之相关的矿床中之所以出现铟的富集,可能与后期地质事件使矿体中的In元素发生活化和再富集有关。

南秦岭双元沟铜矿床成矿斑岩的黑云母和角闪石成分特征及成矿意义

南秦岭山阳—柞水矿集区发育多个斑岩-夕卡岩型Cu-Mo矿床,其中双元沟斑岩型铜矿床的矿体主要赋存于岩体及其与围岩的接触带中。选取双元沟矿床的石英闪长斑岩和花岗闪长斑岩开展岩相学、电子探针和LA-ICP-MS原位微区成分分析,揭示黑云母和角闪石的成分特征及成矿指示意义。双元沟石英闪长斑岩与花岗闪长斑岩的黑云母主量成分特征相近,且具有富Mg,Al,Ti,K,F,Cl和贫Si,Na的特征。角闪石主微量元素差异较大,石英闪长斑岩中角闪石相对花岗闪长斑岩更富Si,Mg,而贫Al,Fe。两类岩体中的角闪石均具轻稀土元素富集,重稀土元素亏损的特征。石英闪长斑岩具有较高的氧逸度,位于HM(Fe_(2)O_(3)-Fe_(3)O_(4))高氧化区。两类斑岩均富挥发分,且花岗闪长斑岩的岩浆更富水(平均为5.30%),指示花岗闪长斑岩更具成矿潜力,含水量是造成二者成矿差异的主要因素。

桂北加里东期越城岭岩体和都庞岭西体黑云母矿物化学特征对比及对成岩成矿指示

加里东期越城岭岩体和都庞岭西体同处于南岭西段W-Sn-Cu多金属成矿带,但二者成矿能力不同。越城岭岩体以铁质黑云母为主,形成于相对低温(平均531℃)和高压(平均277 MPa)环境,具有贫镁(MgO平均8.05%、X_(Mg)=0.39),富铁(FeOT平均22.4%、I_(Fe)=0.61)、铝(Al_(2)O_(3)平均16.8%)等特征;都庞岭西体以镁质黑云母为主,形成于高温(平均687℃)和低压(平均194 MPa)环境,具有富镁(MgO平均11.9%、X_(Mg)=0.56),贫铁(FeOT平均17.0%、I_(Fe)=0.45)、铝(Al_(2)O_(3)平均15.5%)等特征。综合岩相学和前人全岩分析结果表明,越城岭岩体具有S型花岗岩特征,其岩浆可能主要来自上地壳变质泥岩的部分熔融,而都庞岭西体具有I-S过渡型花岗岩的特征,其岩浆可能主要来自壳幔混合源区岩浆岩的部分熔融。越城岭岩体具有变质泥岩源区岩浆岩属性、低氧逸度(log f_(O_(2))=-23.6)、富氟(F平均1.10%、IV(F)=1.62、IV(F/Cl)=6.00,log(f_(H_(2)O)/fHF)^(fluid)=4.78)、高铁指数(XFe=0.58)及高结晶分异程度(log(f_(H_(2)O)/f_(HCl))^(fluid)=5.10,log(fHF/f_(HCl))^(fluid)=0.10)等特征,指示其具有较好的钨及一定的铜成矿潜力;而都庞岭西体具有壳幔混合源区岩浆岩属性、较低的氧逸度(log f_(O_(2))=-17.3)、富氯(Cl平均0.04%,log(fHF/f_(HCl))^(fluid)=-0.36)、中等铁指数(XFe=0.41)及较低的结晶分异度(log(f_(H_(2)O)/f_(HCl))^(fluid)=4.41,log(fHF/f_(HCl))^(fluid)=-0.36)等特征,指示其局部可能有一定的铁成矿潜力。综合分析认为,岩石成因、源区性质以及成岩过程的物化条件是制约越城岭岩体和都庞岭西体不同类型金属成矿能力的重要因素。

黑云母温度计能否用于估计花岗质侵入岩的结晶温度?

为了探讨黑云母温度计是否适用于估计花岗质侵入岩的结晶温度,汇编了国内外典型花岗质侵入体的岩石化学和矿物化学数据,利用Henry等(2005)的黑云母Ti饱和温度计、Li和Zhang(2022)的黑云母全组分温度计估算了岩浆温度,并与Shao等(2020)的锆饱和温度计估算结果进行了对比。结果表明,黑云母Ti饱和温度计估算的温度比锆饱和温度计和黑云母全组分温度计低50~200℃,因此认为黑云母Ti饱和温度计并不适用于估算花岗质侵入岩的结晶温度,而黑云母全组分温度计可以复现S型和I型花岗岩的锆饱和温度计结果。

滇西北红牛-红山铜矿床复式岩体黑云母特征及成岩成矿指示意义

滇西北红牛-红山斑岩-矽卡岩型大型铜矿床位于格咱铜多金属矿集区中部,其成矿作用与晚白垩世花岗质岩浆活动存在密切联系,矿区内发育燕山晚期花岗斑岩-石英二长斑岩复式岩体,矿体主要产于斑岩体以及与斑岩有关的矽卡岩中。铜钼矿化在空间上的分布具有明显的差异性,深部揭露的花岗斑岩发育弱黄铜矿化、辉钼矿化,而石英二长斑岩中发育较强的铜钼矿化,局部出现全岩矿化的特点,总体表现出浅部、接触带矿化程度高,向深部逐渐降低的趋势,导致这种差异的原因尚未明确。在详细的岩相学观察基础上,文章对复式岩体中的黑云母开展了EMPA及LA-ICP-MS原位微区分析,旨在查明矿区花岗斑岩-石英二长斑岩复式岩体形成时的物理化学条件以及导致二者含矿差异性的制约因素。结果表明,2种类型黑云母具有低Al,高Mg、Ti的特征,均属于镁质黑云母;黑云母成分显示红牛-红山燕山晚期复式岩体为具壳幔混源特征的I型花岗岩,属于高温、浅成-超浅成相、高氧逸度岩体。花岗斑岩结晶温度为737~751℃,压力为46~72 MPa,对应深度1.74~2.73 km,平均为2.17 km;石英二长斑岩结晶温度为722~754℃,压力为37~58 MPa,对应深度1.42~2.20 km,平均为1.91 km,氧逸度略高于花岗斑岩。花岗斑岩中黑云母的Ⅳ(F)值为0.91~1.06,Ⅳ(Cl)值为-4.67~-4.48,石英二长斑岩中黑云母Ⅳ(F)值为0.56~0.77,Ⅳ(Cl)值为-5.16~-4.81,与花岗斑岩共存的热液流体log(f_(H2O)/f_(HF))_(fluid)值为1.31~1.47,与石英二长斑岩共存的热液流体log(f_(H2O)/f_(HF))_(fluid)值为0.96~1.17,表明该复式岩体2种岩性均显示高F、Cl特征,石英二长斑岩流体中更富含HCl和HF。这些特征表明红牛-红山燕山晚期复式岩体具有同时发生Cu、Mo矿化的潜力,并且Cu、Mo元素更趋向于在石英二长斑岩中富集。较高的氧逸度和卤素含量可能是导致石英二长斑岩和花岗斑岩含矿差异性的主要原因。