兰坪金顶铅锌矿床泥底辟流体成矿特征初探

兰坪金顶铅锌矿床的成矿过程与油气的生成有许多相似之处,泥底辟构造在金顶铅锌矿床的成矿过程中起着极为重要的作用。首先,随着泥底辟的上侵,塑性泥流夹带大量气体到构造圈闭中释放压力,扩大成矿空间;其次,流体的去气作用在构造圈闭中进行一系列的强改造活动,进而促使铅锌矿体的形成。文章通过对金顶铅锌矿床形成有关的泥底辟流体的来源、流体形成原因、流体在张性-挤压走滑盆地阶段的演化及金顶铅锌矿床成矿的泥底辟流体特征的分析,认为兰坪金顶铅锌矿床的形成与泥底辟构造密切相关,该矿床具泥底辟流体的成矿特征。     

云南金顶铅锌矿成矿流体特征与成矿作用

金顶铅锌矿位于兰坪盆地中部,控矿构造为金顶逆冲推覆构造。流体包裹体及硫同位素研究表明：矿区中的硫属于正常沉积系统,并具有有机生物成因的特点;成矿流体均一温度72.9~490 ℃,盐度为7.4%~16.9%,成矿压力85~230 MPa,成矿流体pH值5.36~7.09,Eh值为-0.44~1.17 V。矿床形成于新生代陆内汇聚构造背景,沘江断裂的长期活动与输送含矿物质热卤水,贯入到金顶穹隆构造,形成“金顶式”Pb-Zn矿床。     

西南三江兰坪盆地大规模成矿的流体动力学过程——流体包裹体和盆地流体模拟证据

中国西南部云南兰坪盆地因金顶Zn-Pn矿床和新发现的白秧坪超大型Cu-Co-Ag矿床而驰名。金顶矿床以白垩系和第三系陆相碎屑岩为主岩,拥有2亿吨矿石,平均品位Zn6.08%、Pb1.29%(1500万吨金属),是目前中国最大的Zn-Pb矿床,也是世界上形成时代最新且唯一产于陆相沉积岩容矿的超大型Zn-Pb矿床。不同于世界上人们公认的沉积岩容矿基本类型,即SST、MVT和Sedex型,金顶矿床也许代表了Zn-Pb矿床的一个新类型。通常认为兰坪盆地大规模成矿流体起源于盆地卤水,流体流动以重力驱动为主,压力体系接近静水压力。但基于矿田内水压破裂观察、流体包裹体研究和盆地流体动力学模拟,我们认为深部超压流体的注入对整个成矿系统起着重要作用。闪锌矿及相关脉石矿物(石英、天青石、方解石、石膏)中流体包裹体观测的均一温度主体在110～150℃,盐度(质量分数)在1.6%～18.0%NaCl;在时间上,大规模成矿主要阶段伴随着流体温度的不断升高和盐度的逐渐降低;在空间上,金顶矿区空间上从东到西,成矿流体温度明显降低,盐度系统性升高。富CO2流体包裹体揭示成矿流体曾高达(513～1364)×105Pa,大大高于静水压力。数值模拟表明,盆地沉积和压实产生的流体超压可以忽略,区域构造推覆也不足以产生如此高的流体压力。我们认为成矿流体超压很可能是幔源流体注入引起的;幔源含矿的相对高温低盐度流体沿导矿构造注入金顶穹隆构造-岩性圈闭并与其中富H2S的相对低温高盐度卤水混合是兰坪盆地大规模成矿的关键动力学过程。这个特殊的流体动力学过程和成矿系统,使兰坪盆地的成矿有别于世界其他沉积盆地已知的成矿作用。     

辽河盆地大民屯凹陷流体压力场研究

综合利用泥岩声波时差、实测地层压力和地震资料 ,分析了辽河盆地大民屯凹陷的地下流体压力场特征 .研究结果表明 :(1)本区泥岩压实类型可划分为正常压实 -常压型、单段欠压实 -弱超压型和双段欠压实 -强超压型三大类 ;(2 )油层压力梯度接近于 1,多属正常压力系统 ;(3)利用地震资料研究平、剖面压力场特征具有较高的可行性与可靠性 ;(4)现今剖面压力系统由浅部正常压力、中部弱超压和深部强超压 3个部分组成 ,断裂系统、不整合面和相互连通的孔隙系统及底辟构造组成了凹陷内流体纵、横向输导的复杂网络系统 ;(5 )规模较大断层两侧的剩余压力和压力系数具较明显的差异性 ,断层对压力的形成、演化与分布起着重要的控制作用 ;(6 )欠压实与烃类生成是本区超压形成的主导机制     

DF1-1底辟区构造应力场及渗流场演化的数值模拟研究

DF1-1底辟区是莺歌海盆地内超压流体最活跃的地带之一.超压流体的活动直接受控于构造应力及其形成的不同类型的断裂和裂隙构成的输导系统.从底辟区大规模流体垂向活动以及幕式活动的特征来看, 流体流动的动力主要是由于垂向压差的存在以及渗流场变化引起的局部应力场(包括热应力场) 的作用所致.在详细研究底辟区的构造及流体活动关系的基础上, 对底辟区构造应力场及渗流场的演化进行了模拟.结果显示: 构造运动引起的应力场决定了DF1-1底辟区油气沿主要断裂系走向迁移的总趋势, 在底辟区流体从底辟的两侧向其中心运移, 由底辟体中向上运移为主; 高压流体产生的热应力控制局部应力场状况及油气运移方向, 驱动流体向底辟体顶部运移, 当热应力值过大时有可能改变应力场状况以及油气运移总趋势.      

辽河盆地大民屯凹陷流体压力场研究

综合利用泥岩声波时差、实测地层压力和地震资料, 分析了辽河盆地大民屯凹陷的地下流体压力场特征.研究结果表明: (1) 本区泥岩压实类型可划分为正常压实-常压型、单段欠压实-弱超压型和双段欠压实-强超压型三大类; (2) 油层压力梯度接近于1, 多属正常压力系统; (3) 利用地震资料研究平、剖面压力场特征具有较高的可行性与可靠性; (4) 现今剖面压力系统由浅部正常压力、中部弱超压和深部强超压3个部分组成, 断裂系统、不整合面和相互连通的孔隙系统及底辟构造组成了凹陷内流体纵、横向输导的复杂网络系统; (5) 规模较大断层两侧的剩余压力和压力系数具较明显的差异性, 断层对压力的形成、演化与分布起着重要的控制作用; (6) 欠压实与烃类生成是本区超压形成的主导机制.      

莺歌海盆地泥-流体底辟构造成因机制与天然气运聚

莺歌海盆地的泥 -流体底辟构造发育演化是区域构造应力场变化和超压体系形成演化的结果。与盆地构造类型密切相关的不均衡压实和热作用引起盆地超压体系的发育 ,而区域构造应力场变化则导致盆地中中新世以泥底辟作用为主 ,晚中新世—第四纪以流体底辟作用为主 ,其中 ,早期泥底辟阶段形成的构造形态对晚期流体底辟作用有显著的控制作用。在莺歌海组浅层底辟圈闭中 ,圈闭形成期与中新统气源岩生烃过程的匹配是造成含不同天然气组分的流体发生幕式充注的主要原因     

DFl—1底辟区构造应力场及渗流场演化的数值模拟研究

DFl—1底辟区是莺歌海盆地内超压流体最活跃的地带之一．超压流体的活动直接受控于构造应力及其形成的不同类型的断裂和裂隙构成的输导系统．从底辟区大规模流体垂向活动以及幕式活动的特征来看，流体流动的动力主要是由于垂向压差的存在以及渗流场变化引起的局部应力场(包括热应力场)的作用所致．在详细研究底辟区的构造及流体活动关系的基础上，对底辟区构造应力场及渗流场的演化进行了模拟．结果显示：构造运动引起的应力场决定了DFl—1底辟区油气沿主要断裂系走向迁移的总趋势，在底辟区流体从底辟的两侧向其中心运移，由底辟体中向上运移为主；高压流体产生的热应力控制局部应力场状况及油气运移方向，驱动流体向底辟体顶部运移，当热应力值过大时有可能改变应力场状况以及油气运移总趋势．     

闽西南马坑矽卡岩型铁矿床扩容构造控矿机制及深部找矿意义

文章基于岩石力学及分形统计分析,结合野外地质调查,探讨了扩容构造控矿机制及其在福建马坑铁矿床成矿过程中的作用。指出马坑铁矿床成矿过程与构造变形作用造成的扩容机制密切相关,其中,锯齿状断裂扩容构造及流体超压作用扩容是马坑铁矿床除接触交代作用外成矿的关键因素。锯齿状断裂扩容构造形成于伸展剪切作用,造成矿体沿倾向的尖灭再现。成矿流体超压扩容主要是由于流体沸腾作用引起,使岩石发生角砾岩化,其中大规模角砾岩是矿体的有利赋存部位。福建马坑矿区深部及外围找矿,应重点关注大规模高强度的汇流扩容区。     

沉积盆地超压系统演化、流体流动与成藏机理

压实不均衡和生烃 ,特别是生气作用是可独立产生大规模超压的主要机制。根据超压顶面的几何形态、超压的发育机制、超压系统的内部结构和演化 ,可将超压系统分为封隔型超压系统和动态超压系统 2类。超压流体的排放包含 2个层次 :从超压泥岩向邻近输导层的初次排放和从超压系统向上覆常压系统或相对低超压系统的二次排放。封隔型超压系统的流体排放主要通过周期性顶部封闭层破裂进行 ,动态超压系统的流体排放可能主要通过断裂或其它构造薄弱带、超压顶面隆起点和超压系统内构造高点处的水力破裂集中进行。超压盆地油气倾向于在静水压力系统富集 ,并具有幕式充注特征 ,但超压系统既可发育商业型油藏 ,也可形成大型气藏。     

http://www.sciencedirect.com/science/article/pii/S1674987111000764

The Jinding Zn-Pb deposit has been generally considered to have formed from circulating basinal fluids in a relatively passive way,with fluid flow being controlled by structures and sedimentary facies,similar to many other sediments-hosted base metal deposits.However,several recent studies have revealed the presence of sand injection structures,intrusive breccias,and hydraulic fractures in the open pit of the Jinding deposit and suggested that the deposit was formed from explosive release of overpres-sured fluids.This study reports new observations of fluid overpressure-related structures from underground workings(Paomaping and Fengzishan).which show clearer crosscutting relationships than in the open pit.The observed structures include:I) sand(±rock fragment) dikes injecting into fractures in solidified rocks:2) sand(±rock fragment) bodies intruding into unconsolidated or semi-consolidated sediments;3) disintegrated semi-consolidated sand bodies;and 4) veins and breccias formed from hydraulic fracturing of solidified rocks followed by cementation of hydrothermal minerals.The development of ore minerals(sphalerite) in the cement of the various clastic injection and hydraulic fractures indicate that these structures were formed at the same time as mineralization.The development of hydraulic fractures and breccias with random orientation indicates small differential stress during mineralization,which is different from the stress field with strong horizontal shortening prior to mineralization. Fluid flow velocity may have been up to more than 11 m/s based on calculations from the size of the fragments in the clastic dikes.The clastic injection and hydraulic fracturing structures are interpreted to have formed from explosive release of overpressured fluids,which may have been related to either magmatic intrusions at depth or seismic activities that episodically tapped an overpressured fluid reservoir.Because the clastic injection and hydraulic structures are genetically linked with the mineralizing fluid source,they can be used as a guide for mineral exploration.     

云南金顶铅锌矿床成矿物质来源及有机成矿作用

分析了金顶铅锌矿床同位素及生物标志化合物特征,探讨了矿床成矿物质来源及有机成矿作用。结果表明,矿石铅主要来自上地幔,成矿流体主要为地幔流体和盆地卤水。矿区有机质的母质来源以低等水生生源的海藻类为主,同时伴随有一定量的陆源高等植物组分的输入,有机质来源于三叠纪三合洞组碳酸盐岩地层。有机质在成矿作用中可能起到的作用有：还原硫酸盐提供成矿所需的硫源;形成有机一金属络合物,活化运移成矿金属元素;改变成矿物理化学环境对成矿物质的还原沉淀作用。     

Cenozoic Mineralization in China, as a Key to Past Mineralization and a Clue to Future Prospecting

Many Cenozoic metal deposits have been found during the past decade. Among them, the Fuwan Ag deposit in Guangdong is the largest Ag deposit in China. Besides, the largest Cu deposit of China in Yulong, Tibet, the largest Pb-Zn deposit of China in Jinding, Yunnan, and the largest Au deposit of China in Jinguashi,Taiwan, were also formed in the Cenozoic. Why so many important "present" deposits formed during such a short period of geological history is the key problem. The major reason is that different tectonic settings control different kinds of magmatic activity and mineralization at the same time. In southwestern China, porphyry-type Cu deposits such as Yulong were formed during the early stage of the Himalayan orogeny, sediment-hosted Pb-Zn deposits such as Jinding were formed within intermontane basins related to deep faults, and carbonatite-related deposits such as the Maoniuping REE deposit and alkalic magmatic rock-related deposits such as the Beiya Au deposit originated from the mantle source.     

Geologic, fluid inclusion and isotopic characteristics of the Jinding Zn–Pb deposit, western Yunnan, South China: A review

With a reserve of  200 Mt ore grading 6.08% Zn and 1.29% Pb (i.e., a metal reserve of  15 Mt) hosted in Cretaceous and Tertiary terrestrial rocks, the Jinding deposit is the largest Zn–Pb deposit in China, and also the youngest sediment-hosted super giant Zn–Pb deposit in the world. The deposit mainly occurs in the Jinding dome structure as tabular orebodies within breccia-bearing sandstones of the Palaeocene Yunlong Formation (autochthonous) and in the overlying sandstones of the Early Cretaceous Jingxing Formation (allochthonous). The deposit is not stratiform and no exhalative sedimentary rocks have been observed. The occurrence of the orebodies, presence of hangingwall alteration, and replacement and open-space filling textures all indicate an epigenetic origin. Formation of the Jinding Zn–Pb deposit is related to a period of major continental crust movement during the collision of the Indian and Eurasian Plates. The westward thrusts and dome structure were successively developed in the Palaeocene sedimentary rocks in the ore district, and Zn–Pb mineralisation appears to have taken place in the early stage of the doming processes.The study of fluid inclusions in sphalerite and associated gangue minerals (quartz, celestine, calcite and gypsum) shows that homogenisation temperatures ranged from 54 to 309 °C and cluster around 110 to 150 °C, with salinities of 1.6 to 18.0 wt.% NaCl equiv. Inert gas isotope studies from inclusions in ore- and gangue-minerals reveal 2.0 to 15.6% mantle He, 53% mantle Ne and a considerable amount of mantle Xe in the ore-forming fluids. The Pb-isotope composition of ores shows that the metal is mainly of mantle origin, mixed with a lesser amount of crustal lead. The widely variable and negative δ³⁴S values of Jinding sulphides suggest that thermo-chemical or bacterial sulphate reduction produced reduced sulphur for deposition of the Zn–Pb sulphides. The mixing of a mantle-sourced fluid enriched in metals and CO₂ with reduced sulphide-bearing saline formation water in a structural–lithologic trap may have been the key mechanism for the formation of the Jinding deposit.The Jinding deposit differs from known major types of sediment-hosted Zn–Pb deposits in the world, including sandstone-type (SST), Mississippi Valley type (MVT) and sedimentary-exhalative (SEDEX). Although the fine-grained ore texture and high Zn/Pb ratios are similar to those in SEDEX deposits, the Jinding deposit lacks any exhalative sedimentary rocks. Like MVT deposits, Jinding is characterised by simple mineralogy, epigenetic features and involvement of basinal brines in mineralisation, but its host rocks are mainly sandstones and breccia-bearing sandstones. The Jinding deposit is also different from SST deposits with its high Zn/Pb ratios, among other characteristics. Most importantly, the Jinding deposit was formed in an intracontinental terrestrial basin with an active tectonic history in relation to plate collision, and mantle-sourced fluids and metals played a major role in ore formation, which is not the case for SEDEX, MVT, and SST. We propose that Jinding represents a new type of sediment-hosted Zn–Pb deposit, named the ‘Jinding type’.     

REE Geochemistry of the Lead—Zinc Ores from the Jinding Lead—Zinc Deposit,Lanping,Yunnan

Nineteen volcanic and magmatic rock samples were collectecd from the Jinding leadzinc deposit and its surrounding areas in Yunnan.The ICP and AES analyses,feferred to the previous results,show that the metal minerals and altered rocks in the Jinding lead-zinc deposit display a decreasing trend of ∑REE from the early to late stages of mineralization,and similarities in REE distribution patterns,indicating that the ore fluids are characterized by high LREE enrichment,markedly negative δCe anomaly and slight δEu anomaly.These REE distribution paterns exhibit striking similarities to those of the Pliocene trachyte in the study area,both of which are similar in ∑REE,LREE/HREE ratio,δEu and δCe.The ore fluids besides the basin fluids in the deposit are also closely related to those associated with Pliocene trachyte magmas.     

Modeling of fluid pressure evolution related to sediment loading and thrust faulting in the Lanping basin: Implications for the formation of the Jinding Zn–Pb deposit, Yunnan, China

The Jinding Zn–Pb deposit occurs in Cretaceous and Paleocene siliciclastic rocks (mainly sandstones) in the Meso-Cenozoic Lanping basin, western Yunnan, China. With a reserve of approximately 200 Mt of ore containing 6.1% Zn and 1.3% Pb, Jinding is the largest sandstone-hosted Zn–Pb deposit in the world. Most previous studies assumed that the mineralizing fluids were derived from within the basin (including meteoric recharge), and the fluid flow was driven by topographic relief under a hydrostatic regime. In contrast, we propose that the mineralizing system was strongly overpressured based on observations of hydraulic fractures and fluid inclusion data. Numerical modeling results indicate that the overpressures could not have been produced by normal sediment compaction. Thrust faulting and input of mantle-derived fluids are likely responsible for the building-up of the high overpressures. The special hydrodynamic regime and potential contribution of mantle-derived fluids to the mineralizing system distinguish Jinding from other known sedimentary basin-related Pb–Zn deposits.     

3D geological architecture and ore -controlling structures of the Paomaping Zn-Pb deposit at the Jinding ore field,Lanping County,SE Tibetan PlateauSCIEI北大核心CSCD

滇西北金顶超大型铅锌矿田位于青藏高原东南缘兰坪中-新生代盆地中部,是三江成矿带中南段最典型的密西西比河谷型(MVT)矿床之一,其构造控矿和盆地流体成矿特征明显受控于印度-欧亚大陆碰撞有关的区域挤压构造。近年来,矿床浅部地质条件与资源状况已被充分揭露,但其深部地质结构、构造控矿差异性仍不清楚,这也制约了成矿预测和找矿新发现。本文以矿田东北部的跑马坪大型隐伏矿床为研究对象,利用三维地质建模及空间分析方法,识别矿化空间变化及其与断层、不整合面和地层岩性的配置关系,分析构造控矿规律及可能的流体运聚趋势。结果表明,跑马坪铅锌矿床的成矿作用与近E-W向挤压构造对中新统金顶砂泥岩(Mio-j)与上三叠统三合洞组(T_(3)s)不整合面的差异性破坏关系密切,近NS和NE向逆断层与NW向走滑-掀斜断层组合是最重要的控矿构造。其中,近NE向逆断层与不整合面是成矿流体运聚的主要通道,而近于平行的NW向走滑-掀斜断层上盘的T_(3)s高孔渗性角砾状灰岩、含灰岩角砾砂岩及裂隙带因为富含H_(2)S等还原性流体而成为与Mio-j富含金属氧化性盆地卤水混合和金属沉淀就位的最有利空间。由此,逆断层和走滑-掀斜断层组合、特定地层岩性与不整合面联合控制了流体汇聚与混合成矿作用,断层沟通了同位叠加的上三叠统油气藏储层和渐新统-中新统盆地卤水(带),这是铅锌成矿的关键。该成矿模型在金顶矿田及邻区与类似地区均具有普遍指导意义。最后,本文预测沿跑马坪矿区深部及其南北侧延伸区域还存在多条NE向隐伏控矿断层,其成矿潜力大,是下一步找矿勘查的有利靶区。     

论云南兰坪金顶超大型铅锌矿床的成因

在前人大量工作和资料积累的基础上,从成矿构造地质背景、容矿系统、容矿岩石的归属与成因、成矿时代和成矿物质来源方面论述了云南兰坪金顶超大型铅锌矿的成因,指出金顶超大型铅锌矿床是新生代陆陆碰撞造山背景下,在晚始新世至渐新世（大约33Ma）区域挤压推覆转变为区域拉张伸展构造环境转换时期,幔源岩浆和热流驱动盆山转换前被封闭在裂谷或前陆盆地深部富含油气、膏盐和金属的流体,沿着造山带两组伸展构造交汇部位上升,在构造圈闭环境下,通过角砾岩侵位—流砂底辟—流体排泄—金属淀积的产物。