四川平武银厂金矿勘探复杂地层钻进技术

四川平武银厂金矿区钻探施工中遇到漏失、缩径、岩心破碎、易孔斜和钻孔事故频发等施工难题,施工难度极大。本文结合地层特点,通过采用绳索取心液动锤、高密度低失水泥浆体系、跟管钻进等工艺技术措施,提高了钻进效率和施工质量,大幅度减少了孔内事故的发生,为顺利完成钻孔施工任务奠定了坚实的基础。     

塔里木陆块西北缘萨热克砂岩型铜矿床构造-流体演化对成矿的制约

塔里木陆块西北缘萨热克砂岩型铜矿床构造演化、流体演化与成矿之间具有密切关系,处于一个统一系统中。矿床成岩期方解石中包裹体水的δD值为-65.3‰~-99.2‰,改造成矿期石英包裹体水的δD值为-77.7‰~-96.3‰,成岩成矿期成矿流体δ~(18)OH_2O变化范围为-3.22‰~1.84‰,改造成矿期成矿流体δ~(18)OH_2O变化范围为-4.26‰~5.14‰,指示萨热克铜矿成岩期、改造期成矿流体主要为中生代大气降水及其经水岩作用而成的盆地卤水。矿石中辉铜矿δ~(34)S值为-24.7‰~-15.4‰,指示硫主要源自硫酸盐细菌与有机质还原,部分源于有机硫。构造与成矿流体演化对砂岩铜矿成矿起关键制约作用。盆地发展早期强烈的抬升运动使盆地周缘基底与古生界剥蚀,为富铜矿源层的形成提供了丰富物源,至晚侏罗世盆地发展晚期,长期演化积聚的巨量含矿流体在库孜贡苏组砾岩胶结物及裂隙中富集,在萨热克巴依盆地内形成具有经济意义的砂岩型铜矿床。     

Genesis and Metallogenic Process of the Lujing Uranium Deposit,Southwest Jiangxi Province,China: Constraints of Micropetrography and S–C–O Isotopes

The Lujing uranium deposit, located in the southeastern part of the Nanling metallogenic province, is one of the representative granite‐related hydrothermal uranium deposits in South China. Basic geology, geochemistry, and geochronology of the deposit have been extensively studied. However, there is still a chronic lack of systematic research on the genesis and metallogenic process of the deposit. Thus, we recently carried out an electron microprobe and stable isotopic analysis. The main research results and progresses are as follows: Uranium minerals in this deposit include coffinite, pitchblende, and uranothorite, and small amounts of uranium exist in accessory minerals in the form of isomorphism. Coffinite, which occurs predominantly as the pseudomorphs after pitchblende, also occurs as a primary mineral and is locally formed from the remobilization of uranium from adjacent uranium‐bearing minerals. The mineralizing fluid was originally composed of a magmatic fluid generated by late Yanshanian magmatism. The high As content of pyrite in ores may reflect the addition of meteoric water, or the formation water (or both), to the magmatic hydrothermal system. The δ³⁴S values vary from −14.4‰ to 13.9‰ (mean δ³⁴S = −3.9‰), showing a range that is similar to nearby Cambrian metamorphic strata and Indosinian granites, indicating that these host rocks represent the source of sulfur; however, the possibility of a mantle source cannot be completely ruled out. According to our new isotopic data and recent Pb isotopic data, we conclude that the uranium in ores was derived by leaching dominantly from the uranium‐rich host rocks, especially the Cambrian metamorphic strata. The δ¹³C_PDB values (−8.75‰ to 1.40‰; mean δ¹³C_PDB = −5.41‰) and δ¹⁸O_SMOW values (5.45–18.62‰; mean δ¹⁸O = 13.02‰) of reddish calcite from the ore‐forming stage suggest that the CO₂ in the mineralizing fluids was derived predominantly from the mantle, with a small component contributed by marine carbonates. Based on these new data and previous research results, this paper proposes that uranium metallogenesis in the Lujing deposit is closely associated with mafic magmatism resulting from crustal extension during the Cretaceous to Paleogene in South China.     

Rb–Sr Dating of Gold‐Bearing Pyrite in the Jinchang Porphyry Cu–Au Deposit,Heilongjiang Province,NE China

The Jinchang Cu–Au deposit in Heilongjiang Province, NE China, is located in the easternmost part of the Central Asian Orogenic Belt. Rb–Sr analyses of auriferous pyrite from the deposit yielded an isochron age of 113.7 ±2.5 Ma, consistent with previously reported Re–Os ages. Both sets of ages represent the timing of Cu–Au mineralization because (i) the pyrite was separated from quartz–sulfide veins of the mineralization stage in granite porphyry; (ii) fluid inclusions have relatively high Rb, Sr, and Os content, allowing precise measurement; (iii) there are no other mineral inclusions or secondary fluids in pyrite to disturb the Rb–Sr or Re–Os decay systems; and (iv) the closure temperatures of the two decay systems are ≥500°C (compared with the homogenization temperatures of fluid inclusions of 230–510°C). It is proposed that ore‐forming components were derived from mantle–crust mixing, with ore‐forming fluids being mainly exsolved from magmas with minor amounts of meteoric water. The age of mineralization at Jinchang and in the adjacent regions, combined with the tectonic evolution of the northeast China epicontinental region, indicates that the formation of the Jinchang porphyry Cu–Au deposit was associated with Early Cretaceous subduction of the paleo‐Pacific Plate.     

庐枞火山岩盆地南部拔茅山铜矿深部找矿潜力分析

位于庐枞火山岩盆地南部的拔茅山铜矿,是细脉带蚀变岩型脉状铜矿的代表。研究表明,其深部具有斑岩型铜矿的勘探潜力。为了进一步明确其深部找矿潜力,针对研究区斑岩型、热液型铜多金属矿的岩体、断裂、接触带等主要控矿因素,利用高精度磁法和可控源音频大地电磁测深(CSAMT)成果,分别对拔茅山岩体的分布、产状和深部形态及其与围岩的接触带特征进行了剖析。在此基础上,通过与沙溪斑岩铜矿地质、物探异常特征的类比,指明了研究区的找矿方向和有利找矿部位,为进一步找矿提供了思路和依据。     

安徽茶亭铜金矿床赋矿石英闪长玢岩黑云母成分特征及成岩成矿指示意义

安徽宣城茶亭矿床位于长江中下游成矿带东南缘的南陵-宣城盆地内,是近年来该盆地内新发现的大型斑岩型Cu-Au矿床。石英闪长玢岩是茶亭矿床主要的赋矿岩石,文章从石英闪长玢岩的造岩矿物黑云母入手,利用EMPA及LA-ICP-MS等原位微区分析方法,对黑云母进行了详细的矿物化学分析,旨在查明赋矿石英闪长玢岩形成的物理化学条件,并探讨其成岩成矿意义。分析结果表明:茶亭赋矿石英闪长玢岩中黑云母具有高w(TiO_2)、低w(Al_2O_3)的特征,整体富Mg、贫Fe。黑云母温压计算结果表明,在不同深度上,石英闪长玢岩具有相似的结晶温度及压力,其结晶温度为746～773℃,压力为44～85 MPa,对应深度为1.7～3.3 km,平均为2.47 km,显示石英闪长玢岩侵位深度相对较浅。黑云母中高的氧化系数(0.613～0.864)、高Mg#(0.557～0.864),以及w(MgO)介于14.73%～15.86%,均显示石英闪长玢岩为壳幔混源,并且以幔源为主。黑云母成分显示石英闪长玢岩形成于较高氧逸度条件下。浅部岩体具有较高的X_(Mg)值,表明浅部岩体氧逸度较高,可能指示随着岩浆的不断演化,残余岩浆的氧逸度不断降低。同时,石英闪长玢岩黑云母相对一般斑岩型铜矿具有较高的w(Cu),并且高Cl、低F。这些特征均有利于茶亭Cu-Au矿床的形成。     

内蒙古丰镇市泉子沟斑岩钼矿床成岩成矿年代学及其地质意义

泉子沟斑岩钼矿床位于内蒙古丰镇市,地处华北克拉通北缘内蒙古台隆凉城断隆内。矿区出露一套燕山期花岗质杂岩体——红娘山杂岩体,主要由中粗粒花岗岩、似斑状花岗岩和石英斑岩组成,钼矿体主要赋存于似斑状花岗岩中。文章在详细的野外地质调查基础上,对泉子沟矿床的成岩成矿时代进行了详细研究,并探讨了地质意义。5件辉钼矿样品的Re-Os模式年龄介于(158.8±2.2)Ma~(161.5±2.2)Ma之间,其加权平均值为(159.8±1.0)Ma(MSWD=0.92),等时线年龄为(161.7±3.1)Ma(MSWD=1.40)。红娘山杂岩体LA-ICP-MS锆石U-Pb年龄分别为:中粗粒花岗岩结晶年龄为(173±1)Ma(MSWD=0.88),似斑状花岗岩侵位年龄为(162±1)Ma(MSWD=0.40),石英斑岩结晶年龄为(160±2)Ma(MSWD=1.90)。辉钼矿Re-Os和锆石U-Pb定年结果表明,泉子沟钼矿床形成于晚侏罗世早期,成矿与似斑状花岗岩关系密切。泉子沟钼矿床的辉钼矿w(Re)介于16.49×10~(-6)~32.87×10~(-6),暗示成矿物质主要来自下地壳。     

黑龙江省塔河县宝兴沟金矿床中生代侵入岩及其对成矿作用的制约

宝兴沟金矿床为近年来在漠河前陆盆地南缘新发现的大型金矿床。区内发育石英闪长岩、闪长玢岩、花岗细晶岩等侵入岩,矿体主要产于石英闪长岩、闪长玢岩内部及其与二十二站组砂岩的内外接触带中。地球化学研究表明,石英闪长岩具高钾、低钛、富碱特征,花岗细晶岩具高硅、高钾、低钛、富碱特征,二者均为高钾钙碱性系列岩石,富集大离子亲石元素Rb、Ba、Sr等,亏损高场强元素Nb、Ta、Ti和重稀土元素Yb、Y,但二者稀土元素特征和配分曲线差异较大,不具成因联系。矿石与石英闪长岩、闪长玢岩具有相似的微量元素、稀土元素组成和稀土元素配分曲线,表明石英闪长岩、闪长玢岩为成矿提供了热液和成矿物质等,与成矿具有密切的成因联系。LA-ICP-MS锆石U-Pb同位素测年结果显示,石英闪长岩成岩时间为118.13~121.77 Ma,限定了宝兴沟金矿床的形成时间不早于118Ma,为早白垩世,形成于太平洋板块俯冲后的伸展环境。漠河前陆盆地除中-晚侏罗世侵入岩外,早白垩世中酸性侵入岩对区域成矿也具有重要的作用,是今后找矿的重要方向之一。     

延边农坪富金斑岩铜矿床花岗闪长斑岩年代学、地球化学及其地质意义

农坪金铜矿床位于吉林省珲春市春化境内,是一座中型富金斑岩型矿床。文章采用LA-ICP-MS锆石U-Pb定年方法,对农坪含矿花岗闪长斑岩进行了锆石U-Pb分析,获得加权平均年龄为(95.6±1.6)Ma,表明花岗闪长斑岩形成于晚白垩世。地球化学分析显示,农坪含矿斑岩富碱(5.6%~6.7%),高Mg#(47~55)、富集LILE和LREE,亏损HFSE和HREE,高Sr/Y(32~57)、(La/Yb)N(10~21)比值,具有埃达克质岩石的特点,岩浆的形成可能存在壳幔混合及分离结晶作用。结合区域大地构造背景和同一构造带上其他矿床的形成时代和特征,笔者认为农坪矿床是晚白垩世古太平洋板块向欧亚大陆斜向俯冲背景下陆缘弧岩浆作用及热液活动的产物。     

新疆伊吾县宝山铁矿床矽卡岩成因研究

宝山铁矿床位于东准噶尔库兰卡孜干-北塔山-纸房-琼河坝岛弧带东段。宝山铁矿中矽卡岩与铁矿体密切共生,是重要的找矿标志。研究区矽卡岩中石榴子石、透辉石单矿物电子探针分析结果显示,石榴子石属于钙铁榴石-钙铝榴石系列,透辉石属于透辉石-钙铁辉石系列。矽卡岩中高场强元素(如Nb、Ta、Zr、Hf)相对亏损,稀土元素表现出LREE富集,HREE亏损的特点。∑REE为39.90×10~(-6)~178.43×10~(-6),∑LREE/∑HREE比值1.64~7.53,(La/Yb)N比值为1.32~10.10,轻、重稀土元素分异程度较弱,与玄武质凝灰岩具有相似的地球化学特征,这说明矽卡岩是玄武质凝灰岩受后期岩浆热液改造形成,随着温度和压力降低,磁铁矿沉淀形成铁矿体。