西藏冈底斯斑岩铜矿带驱龙铜矿成矿流体特征及其演化

驱龙铜矿是西藏冈底斯斑岩铜矿带东段典型的斑岩型铜矿床.流体包裹体研究显示,与成矿有关的包裹体主要分为液相包裹体、气相包裹体和含子矿物多相包裹体3类,它们的均一温度为190℃～510℃;盐度为0.5～52.5 wt%NaCleq.激光拉曼显微探针(LRM)分析表明,各类包裹体中气、液相成分以H2O为主.含子矿物多相包裹体与不同气相充填度的液相包裹体、气相包裹体共存,且均一温度相近,但盐度相差很大,表明成矿流体经历了沸腾作用.从蚀变矿物组合、流体包裹体显微测温分析及LRM分析可以看出,驱龙斑岩铜矿床成矿流体富含Cl-、SO2-4、Na 、K 、Ca2 、CO2-3,具有较高盐度和较强的Cu溶解能力.     

西藏驱龙超大型斑岩铜矿的成因：流体包裹体及H O同位素证据

与多数产于岩浆弧环境中的斑岩铜矿不同,西藏冈底斯带斑岩铜矿形成于碰撞造山环境,查明其形成过程有助于理解非岩浆弧环境中斑岩铜矿床的成因.为此,选择冈底斯带最大的斑岩铜矿--驱龙斑岩铜矿进行解剖,通过对矿床岩浆-热液过程形成的各类脉体详细的流体包裹体研究,以及不同蚀变阶段蚀变矿物的H-O同位素研究发现:引起矿床早期蚀变(钾硅酸盐化)与矿化的流体并非通常认为的高盐度岩浆热液,而是直接从岩浆房出溶的中等盐度(约9% NaCl)、近临界密度的高温(550～650℃)气相;气相近临界密度的特征表明,早期蚀变与矿化形成于较高的压力(105±15～90±20 MPa)条件下,用静岩压力估算,对应的古深度在4.2±0.6～3.6±0.8 km之间,成矿后(约16 Ma)矿区发生了至少3～3.5 km的剥蚀;与高盐度流体相比,中等盐度气相与熔体密度差较大,很难在斑岩体顶部聚集并集中释放,而连续释放则直接导致矿床含矿斑岩体与Cu、Mo矿体时空关系的解耦,并造就了矿床早期蚀变范围大、但强度弱,矿化范围大、但品位低的矿床地质特征;成矿物质的沉淀并非温度降低的结果,而是因压力降低及气相中S大量减少所致.总之,驱龙斑岩铜矿是一类成矿与低密度气相有关的斑岩铜矿类型,其蚀变-矿化特征及成矿过程与高盐度流体引发的斑岩矿床类型有所不同,意识到斑岩矿床蚀变及矿化特征与矿床成因的密切关系,对矿床勘查将具有重要的现实意义.     

西藏驱龙超大型斑岩铜矿床:地质、蚀变与成矿

驱龙超大型矿床是一个产于后碰撞伸展环境下、与大洋俯冲无关的新型斑岩铜矿。文章通过对驱龙铜矿床地质、蚀变与矿化的详细研究,建立了驱龙中新世岩浆演化序列,初步查明了岩浆浅成侵位的构造控制要素,厘定了主要的围岩蚀变类型及空间展布规律,查明了引起各期蚀变事件的地质记录及矿化的空间分布规律,并探讨了成矿物质沉淀的机制,初步建立了该矿床的成矿模型。研究表明,驱龙铜矿中新世斑岩是闪长质深部岩浆房不断演化的产物,花岗闪长岩中新发现的、结晶时间为22.2Ma左右的闪长质包体可近似代表深部岩浆房组分,依次产出的花岗闪长岩、呈岩株或岩枝产出的P斑岩、X斑岩及最晚期的闪长玢岩(15.7±0.2)Ma,均为深部岩浆房连续演化的产物,岩浆持续6Ma左右。岩浆演化过程中角闪石、斜长石不断的结晶分异,导致了岩石常量元素、稀土元素及微量元素组成的规律性变化,斑岩埃达克质的特征也因岩浆演化过程中角闪石等矿物的不断结晶分异而引起。X斑岩中锆石的Hf同位素特征表明,岩石可能形成于新生下地壳的部分熔融。大面积产出的花岗闪长岩为驱龙铜矿最主要的含矿围岩,容纳了驱龙矿床70%以上的矿体,主要由斜长石、钾长石和石英组成,具花岗结构-似斑状结构,近EW向产出,其浅成就位可能受背斜控制,其后的各期斑岩均沿该侵位中心上侵,而冈底斯地壳中新世的快速抬升与剥蚀是导致含矿斑岩浅成侵位的根本原因;矿区内的SN向裂隙带既不控岩,也不控矿。浅成侵位的斑岩及深部岩浆房均发生了流体出溶。发生了大量流体出溶的深部岩浆房,是矿区早期蚀变流体的主要来源,显微晶洞构造及单向固结结构(UST)是流体出溶的地质记录。蚀变主要有3种类型,分别为早期的钾硅酸盐化、青磐岩化以及晚期的长石分解。钾硅酸盐化可分为2个阶段,即蚀变矿物以次生钾长石为主的早期钾硅酸盐化和以次生黑云母为主的晚期钾硅酸盐化。青磐岩化因产出的岩石类型不同,蚀变矿物组合具有明显差异性:产于叶巴组地层中的青磐岩化相对较强,蚀变矿物以绿帘石为主;产于花岗闪长岩中的青磐岩化相对较弱,蚀变矿物以绿泥石为主。晚期长石分解蚀变以破坏长石类矿物为特征,蚀变矿物主要为绢云母-绿泥石-粘土等。石英和硬石膏贯穿于上述各种蚀变中。空间上,钾硅酸盐化位于斑岩体及其周围地区,青磐岩化位于钾硅酸岩化外侧。后期形成的长石分解蚀变强烈叠加了早期钾硅酸盐化,介于钾硅酸盐化带与青磐岩化带之间。与早期钾长石化有关的脉体主要为不规则石英-钾长石脉,与晚期黑云母化有关的脉体主要为不规则至板状的石英-硬石膏脉、黑云母脉,与青磐岩化有关的脉体主要为板状的绿帘石-石英脉,与晚期长石分解蚀变有关的脉体主要为板状黄铜矿-黄铁矿脉及黄铁矿脉;在早期钾硅酸盐蚀变与晚期长石分解蚀变转换阶段,发育一组板状的石英-硫化物脉。早期不规则的脉体形成于斑岩结晶早期、矿区裂隙小规模发育阶段;晚期的板状脉体形成于斑岩弱固结或固结之后、矿区大规模连通裂隙发育阶段。驱龙矿区的铜矿化分布较为均一,主体产于花岗闪长岩中,其中,铜矿化主体形成于黑云母化蚀变阶段,转变阶段及长石分解阶段也有大量铜的形成;钼主要形成于转换阶段,长石分解蚀变阶段也有产出。黑云母化阶段,铜的沉淀与角闪石黑云母化、斜长石钾长石化过程中Ca2 的大量释放有关;转换阶段,铜钼矿化可能与压力和(或)温度骤降有关;晚期铜矿化与长石矿化蚀变阶段,斜长石绿泥石化、黑云母绿帘石化过程中Ca2 及Fe2 的释放有关。     

西藏冈底斯斑岩铜矿带成矿流体的扫描电镜（能谱）约束

文章通过对碰撞造山型斑岩铜矿床———冈底斯斑岩铜矿带中的2个典型矿床(驱龙和厅宫)早期钾化石英脉中多相包裹体的扫描电镜/能谱研究,有效地弥补了以往研究中遗漏的成矿流体中有用组分信息,对成矿流体性质及成矿过程有了更为清晰的认识。扫描电镜/能谱研究表明,驱龙、厅宫矿床中多相包裹体中的子矿物,除常见的石盐及钾盐外,还含有重晶石、方解石、黄铜矿、钛铁矿及其他以Fe、Cu_Fe为主要元素的未知矿物。这些结果表明,成矿流体为富含Cu、Fe、Ti、Mn、S等成矿元素的高氧化态岩浆热液;黄铜矿、钛铁矿、重晶石等子矿物与石盐、钾盐子矿物共同产出,暗示直接从斑岩岩浆中出溶的高盐度流体是成矿物质组分搬运的主要载体。     

西藏驱龙超大型斑岩铜矿床成矿流体对成矿的控制

驱龙斑岩铜矿是冈底斯成矿带新发现的规模最大的超大型矿床, 形成于中新世.原生流体包裹体有5种类型, 主成矿阶段均一温度集中于240~650℃之间, 盐度变化于0.18%~52.04%之间, 明显分为高盐度高密度、低盐度低密度2类.可见含子矿物、液相、气相等包裹体共存现象, 且均一温度相近, 盐度相差很大, 表明成矿流体经历了沸腾过程; 氢氧同位素及单矿物微量稀土元素研究表明, 成矿物质主要来源于斑岩岩浆体系, 而成矿流体主要来源于岩浆水、天然热卤水有关的混合水, 且天然热卤水占优势, 属NaCl (F) -KCl (F) -C₂H₆-HCO₃-CaSO₄型流体.成矿流体总体显示出高温、高盐度、高矿化度、高氧逸度的还原性酸性流体特征, 并且富集Na+、K+、F-、Cl-、SO₄2-、CO₂等成分, 以富F-为特征(F-/Cl- > 1, 平均为5.66), 这种特殊性质的流体特别有利于Fe2+、Cu2+等元素的迁移, 并最终在岩浆期后热液期富集成矿, 它是形成驱龙超大型斑岩铜矿床的必要条件; 流体减压沸腾及不同性质流体混合作用是促使金属离子沉淀富集的主要机制.对该矿床成矿深度(0.5~2km) 进行了探讨, 可作为该矿床勘查评价的依据.      

西藏多不杂斑岩铜矿床高温高盐度流体包裹体及其成因意义

多不杂铜矿为班公湖—怒江缝合带上发现的第一处大型斑岩铜矿床,矿床位于羌塘—三江复合板片南缘的多不杂构造岩浆带中。多不杂斑岩铜矿总体上具有典型的斑岩铜矿矿石特征和蚀变分带特点,围绕斑岩体从岩体中心向外,可以划分出三个主要的蚀变带,依次为钾硅化 绢英岩化带、绢英岩化带和黄铁矿化—角岩化带。矿床以岩体内部和外部均发育强烈的磁铁矿化蚀变、而外围青磐岩化带不发育等特征有别于国内其他斑岩铜矿。对斑岩铜矿的流体包裹体特征和均一测温结果表明斑岩铜矿石英含有丰富的流体包裹体,包裹体类型众多,而以大量发育含子矿物多相包裹体为突出特征。子矿物种类有石盐、钾盐、赤铁矿、红钾铁盐、石膏、黄铜矿等,有时一个包裹体含有多达5~6个子矿物,在我国其他斑岩铜矿中是不多见的。金属子矿物大量发育表明流体成矿金属元素含量很高。成矿流体由来自岩浆的高温、高盐度流体和以天水成因为主的中低温、低盐度流体两个流体端员组份组成。高温、高盐度流体为主要成矿流体,以含子矿物多相流体包裹体为代表,其形成温度>450℃,盐度在28%~83%NaClequ.,平均达到58%~60%NaClequ.,流体组分主要属于H2O-NaCl-KCl-FeCl2体系。高温高盐度流体是在浅成条件下于岩浆结晶的最后阶段从浅部岩浆中直接出溶形成的。中低温、低盐度流体主要来源于天水或天水与晚期岩浆热液的混合,温度在360℃以下,盐度3.71%~14.15%NaClequ.。含矿硫化物主要在300~420℃温度区间沉淀,沉淀富集主要与温度降低有关,多不杂斑岩铜矿为与浅成斑岩体侵入有关的高温岩浆热液型斑岩铜矿。与世界上其他斑岩铜矿相比,多不杂斑岩铜矿具有与Bingham和Grasberg等世界级超大型斑岩铜矿相似的流体包裹体和蚀变分带特征,暗示该矿床具备形成超大型斑岩铜矿的潜力。     

西藏冈底斯三处斑岩铜矿床流体包裹体及成矿作用研究

对西藏冈底斯斑岩铜矿带中的驱龙、冲江斑岩铜矿床和与斑岩有关的帮浦铜多金属矿床进行了流体包裹体岩相学、显微测温和激光拉曼探针分析。对斑岩中斑晶石英、硅化脉石英和热液矿物硬石膏内流体包裹体的观测表明，与成矿有关的流体包裹体可以分为气相包裹体、液相包裹体、含子晶的多相包裹体等3类。它们的均一温度变化较大（191～550℃），气相包裹体与含子晶多相包裹体的均一温度相近，主要集中于300～550℃之间。流体的盐度ω（NaCleq）为1．91％～66．75％，含石盐子晶包裹体的盐度ω（NaCleq）范围为32．70％～66．75％。激光拉曼光谱分析表明，子晶以石盐为主，并有较多的黄铜矿；气相包裹体和液相包裹体的气相中含有CO2。低密度的气相包裹体与高密度的液相包裹体、高盐度的含子晶包裹体共生，其均一温度范围一致，但盐度相差较大，指示成矿流体有不混溶作用或沸腾作用。成矿流体来自于岩浆的出溶；金属硫化物直接来源于岩浆。斑晶石英内流体包裹体中的不混溶作用与岩浆的初始沸腾有关；硅化脉石英捕获的流体包裹体与岩浆的二次沸腾有关；而硬石膏内流体包裹体的不混溶与两种不同性质流体的混合作用有关。斑晶石英中包裹体内的黄铜矿子晶是岩浆流体高金属含量的表征而不是矿化开始的标志。冈底斯成矿带内斑岩铜矿的成矿始于岩浆期后高温阶段，随后的高-中温热液阶段是流体大量沉淀矿质的重要时期。     

冈底斯斑岩铜矿带冲江铜矿含矿流体的形成和演化：来自流体包裹体的证据

对冲江斑岩铜矿含矿斑岩中石英斑晶和含矿石英脉中包裹体进行岩相学、显微测温分析、包裹体中气液相成分的激光拉曼显微探针（LRM）分析和子矿物的扫描电镜/能谱（SEM/EDS）分析.研究表明含矿流体来自富含挥发分的岩浆的出溶作用,最初从岩浆中出溶的流体为近饱和的超临界流体,其最低捕获温度在362～389℃左右,盐度在17.7%～18.9%NaCleq左右.随着出溶流体温度压力的下降,超临界流体发生相分离,并分离出低盐度的气相和高盐度的液相.在石英绢云母化阶段进一步发生高盐度液相包裹体的沸腾作用,形成子矿物溶化温度高于气液相均一温度的高盐度包裹体和富气相包裹体.与粘土化有关的流体为流体演化的晚期产物,属低温、低盐度流体.     

藏东玉龙斑岩铜矿床多期流体演化与成矿的流体包裹体证据

通过对王龙斑岩铜矿石英斑晶、辉钼矿石英脉中流体包裹体岩相学、包裹体显微测温分析、包裹体成分的激光拉曼探针分析及包裹体中子矿物的扫描电镜/能谱分析,发现矿化斑岩石英斑晶中发育多期流体包裹体。斑晶中除流体包裹体外尚可见少量熔体包裹体,与斑岩期矿化有关的成矿流体以中高温(200～537℃)、高盐度(29.6～44.7 wt%NaCleq)为特征,与粘土化蚀变有关的流体包裹体以低温、富 Ca 为特征,不同气相充填度的气液两相包裹体与高盐度含子矿物多相包裹体共存,且具有相似的均一温度,显示不混溶流体包裹体特征。温度、压力降低引起的流体不混溶是造成斑岩型矿化矿质沉淀的主要因素,斑岩期流体与浅成低温热液期流体形成于统一的流体系统,为同源演化结果。     

西藏冈底斯斑岩铜矿带厅宫铜矿床流体包裹体研究

厅宫斑岩铜矿床是西藏冈底斯斑岩铜矿带上重要的矿床之一。为了探明该矿床成矿流体的成分及温压条件等物理化学性质，文章对厅宫铜矿各蚀变阶段石英脉及石英斑晶中的流体包裹体进行了显微测温、四极杆质谱、离子色谱和激光拉曼探针分析，结果表明：厅宫铜矿成矿流体为高温、高盐度岩浆热液，成矿事件主要发生在340～380℃，成矿过程中流体发生了沸腾；成矿流体中气相成分以H2O为主，还含有一定量的CO2及少量的CH4、H2S、C2H6等气体；液相中离子以K^＋、Na^＋、Cl^-、SO4^2-、F^-等为主，还含有少量的Ca^2＋、Mg^2＋等；另外，出现大量气泡先消失、子矿物后熔融的Ⅲa类包裹体，表明有些成矿流体可能直接来源于深部岩浆的出溶作用。     

Fluorine in basalts from Iceland

The fluorine content of Icelandic tholeiitic and alkaline basalts matches values found in similar rocks from other areas. Covariation between fluorine and incompatible minor elements such as potassium or phosphorus is found in evolved tholeiites and alkali basalts. Lack of such covariation in primitive olivine tholeiites indicates that fluorine and other incompatible minor and trace elements are not controlled by minerals such as amphibole, mica or apatite in the mantle residue, and that the covariation between these elements in the evolved basalts cannot be inherited from the mantle. Model calculations on rocks from the Langjökull area show that olivine tholeiite suites are, if derived by simple fractional crystallization, enriched in incompatible elements much in excess of the increase due to crystal removal. These observations are taken to indicate that the well documented covariation between fluorine and other incompatible elements is not established until evolution of the basaltic magma has started in crustal holding chambers. The constancy of element ratios and enrichment in excess of what can be accounted for by crystal fractionation or incremental addition of new batches of primitive magmas does indicate (1) mineral control involving amphibole, mica or apatite and (2) addition of fluorine, potassium and phosphorous from an external source. It is argued that this source is the crustal envelope of the holding chamber.     

Chlorine in basalts from Iceland

Chlorine has a higher solubility in basaltic magmas than other volatiles. A theoretical degassing model predicts that less than 10% of the chlorine originally present in the magma is lost to the atmosphere during surface degassing. This prediction is born out by strong correlation between chlorine and nonvolatile elements in samples from recent volcanic eruptions in Iceland. It is concluded that the chlorine content of subaerial basaltic lavas is proportional to the chlorine content of the magmas. Assuming a roughly constant ratio between chlorine and water in the magmatic gas phase and assuming further that this ratio approximates the $\text{Cl}\text{H}{}_2\text{O}$ ratio in sea water and sediments it is possible to assign each basaltic magma a fixed amount of water. The figures thus obtained (0.3–1.2% H₂O) are identical with previously assumed water contents of basaltic magmas.The implied water contents of the melts are discussed in terms of derivation from hydrous mantle phases. It is concluded that such phases can supply only a fraction of the assumed water content, the rest is derived from an additional volatile source in the mantle. The mantle source giving rise to alkali basalts in Iceland has a lower content of volatiles than the tholeiite source.     

Ca-enrichment in olivines from volcanic rocks

Data are presented on the Ca-content of olivines in a range of volcanic rocks from a variety of suites. These include olivine basalts through to trachytes from Gough, St. Helena and Tristan da Cunha Islands; trachytes from central Victoria, Australia, and a leucitite and phonclitic-tephrite series from Bufumbira, Uganda. In olivine crystals from basaltic lavas the Ca- and Mn-contents are low and Fe shows the most significant zoning from core to rim. In Fe-rich olivines from trachytic differentiates Ca and Mn frequently show more significant variation than Fe. While the Mn-content is proportional to the Fe-content of these olivines, Ca-zoning, in many cases, is unrelated to Fe-content. The marked Ca-enrichment in olivines occurs with the absence of plagioclase in the host lavas. The Ca(Al  Na  K) ratio is shown to be related not only to the Ca-content of the olivines in the lava, but may be used to predict olivine stability in evolved compositions.     

First diamonds from placers in Primorie

The paper reports the results obtained by the detailed studying of carbonado (the first find in a gold placer in Primorie) and a collection of diamonds that was confiscated in 1937 from a poaching small digger and was kept safe at the Nezametnyi mine (near the village of Vostretsovo), which had developed this placer deposit. In the concentrate from the placer, carbonado is associated with green corundum, various ilmenite, zircon titanian amphiboles and pyroxenes, rutile, anatase, and fragments of subvolcanic biotite picrites. All of these minerals, native aluminum, and tin occur as inclusions in the diamonds. The carbonado from Primorie was determined to be practically identical to this mineral from Brazil, has a porous structure, is characterized by orange luminescence, contains inclusions of Y, Ce, La, Ba, and Sr phosphates, and has an isotopically light composition of its carbon (¹³C from ?25 to ?32‰). Pores of the carbonado aggregates contain clusters of diamond crystals. The collection of diamonds from an unknown source included six gem-quality transparent crystals, one rounded ballas, two cuboctahedral crystals (one of greenish and the other of silver-gray color, both with outer coats), and one black carbonado grain. The data obtained on the mineralogy of the diamonds have demonstrated that they are completely identical to this mineral from kimberlites and lamproites but bear traces of intense dissolution, fragmentation, multiple recrystallization, and graphitization at defects, which are the most widespread in the ballas. One of the crystals was determined to contain inclusions: aggregates of potassic omphacite (0.50 wt % K₂O) and corundum. Ilmenite (containing up to 8 wt % MgO), titanaugite, kaersutite (4 wt % TiO₂, 0.8 wt % K₂O), and churchite (aqueous phosphate) were obtained from the core of the ballas. The titanaugite, kaersutite, and ilmenite were proven to be compositionally analogous to these minerals from picrites occurring near the placer. The carbon isotopic composition δ¹³C of the cores of the single diamond crystals varies from ?6 to ?11‰. The margins of the grains were proved to be enriched in the light carbon isotope (δ¹³C from ?19 to ?21‰). The gem-quality transparent diamond crystals are characterized by blue luminescence, and the color of luminescence in the carbonado varies from orange red in the bulk of the aggregate to yellowish green in its core. The aforementioned transformations of diamonds were likely caused by their transportation in pipes of micaceous picrites of the Jurassic meymechite complex. The carbonado are thought to correspond to the final stage of the metastable recrystallization (in pores, within the temperature range of the rutile-anatase transition) of the original isotopically heavy diamonds under the effect of various oxidizers (H₂O, CO₂, F, and others) and in the presence of catalytically acting REE, Ti, and P. The primary diamond source (kimberlite or lamproite) can be older and more distant from the study area. The complete geological analogy between the study area in Primorie, Kalimantan Island in Indonesia, and West Australia (where no sources of the placers are known) led us to consider the territory of Primorie as promising for exploration for diamondiferous placers.     

Hardening in porous chalk from precompaction

Knowledge of compactant behavior and the associated subsidence for high porosity carbonate formations is crucial in applications such as enhanced oil recovery. To gain insights into inelastic compaction and failure modes of a porous chalk under different loading histories, triaxial compression experiments were conducted on a high porosity (45 %) chalk, tested using three stress paths: no precompaction (virgin rock), precompacted to 30 MPa, and precompacted to 60 MPa. For the virgin chalk with no precompaction under triaxial compression, the transition from axial splitting to shear fracturing to compaction banding was observed. By precompacting the specimens to mean stresses of 30 and 60 MPa, the brittle failure regime expanded. In 60 MPa precompacted specimens, shear fracture was observed over a larger range of mean stress. Furthermore, precompaction increased the internal friction angle due to permanent volume change, but the cohesion decreased due to damage.     

贵州关岭动物群中的海百合

关岭动物群是由海百合、水生爬行动物、鱼、双壳类、菊石、牙形石等多门类生物组成的动物群,保存在上三叠统瓦窑组近底部.本文仅描述了其中的海百合1属2种:Traumatocrinus kueichouensis Mu, Traumatocrinus guanlingensis sp. nov.,其中Traumatocrinus guanlingensis 为1新种.     

Chemistry of petroleum brines from oil-producing wells in Cretaceous rocks from Southeast Mexico

Brine chemical data obtained from oil wells in Cretaceous oilfields in the Southeastern Basin of Mexico show a complex evolution, with the following main hydrochemical processes: (1) mixing of highly evaporated brines, past the point of halite precipitation with seawater; (2) water/rock interactions between brines and carbonated rocks (dolostones).     

花岗伟晶岩石英流体包裹体中的短链羧酸

用离子色谱法研究了某些花岗伟晶岩中石英流体包裹体浸取液的短链送终酸（甲酸、乙酸、丙酸和草酸）和无机阴离子（氟、氯和硫酸根离子）组成,同时进行了矿物包裹体流体的氢和石英的氧同位素成分测定以及显微计温学研究。结果表明,北京延庆大庄科花岗伟晶岩的石英流体包裹体浸取液中含有少量的甲酸和乙酸。花岗岩演化晚期－伟晶岩阶段的高温水热流体中可以存在短链羧酸。