试论主要类型矿床的形成深度与最大延深垂幅

在大量典型矿床实地调查和国内外综合对比研究的基础上,基于深部找矿的现实需要和存在问题,本文首先回顾评述了主要矿床类型的原始成矿深度,按受控于中下地壳尺度大规模岩浆堆积体的超深成岩浆矿床与受控于流体渗透率制约的中上地壳深成、中成和浅成岩浆热液矿床序列展开。在此基础上尝试探讨主要类型矿床的最大延深垂幅,探讨分析了以Bushveld层状岩体和Voisey’s Bay小岩体为代表的铜镍矿床、驱龙为代表的斑岩铜矿床、Muruntau为代表的造山型金矿、胶东金矿省的已控制延深垂幅、剥蚀程度以及深部可能的延深空间。内生矿床系统具有很宽的成矿深度范围,大型层状岩体的成矿深度可逾20 km,最大矿化垂直延深幅度可达6~8 km。岩浆热液矿床的最大成矿深度以地壳尺度流体渗透的下限为底界,其中造山型金矿床成矿深度最大(约12~15 km),伟晶岩和花岗岩型矿床次之,斑岩型矿床居中(约2~6 km),浅成低温金银矿床深度最浅(1 km至近地表);相应的最大延深垂幅则依次可达4~7 km、2~3 km和1 km。评述了高渗透性的聚矿构造空间、成矿作用顶峰、合适的矿床保存条件等控制因素及部分标志。并对如何确定合理统一的成岩成矿深度(压力)的估算方法以及确定最大成矿深度与矿化体系最大延深幅度的理论依据、判断标志、综合辨识方法体系等未来研究方向进行了展望。     

铜陵地区矽卡岩型独立金矿成矿深度探讨

采用矿床地质法和流体包裹体压力计法,对铜陵地区包村、朝山矽卡岩型独立金矿床的成矿深度进行了估算。据成矿相关岩体特征、金矿体延深、矿石特征等推断金矿化发生于浅成—中浅成环境。根据不同矿化阶段石英、方解石中流体包裹体的显微测温结果,估算成矿压力为650×105～850×105Pa,成矿深度介于2.5～3.2km,与矿床地质特征反映的成矿深度基本吻合,也与国内外同类矿床研究结果相符。综合认为铜陵地区矽卡岩型独立金矿床成矿深度为中浅成,脆性构造裂隙空间的压力骤然降低引起的流体不混溶和流体沸腾是金富集成矿的主要原因。     

小秦岭成矿带金矿化垂向分带规律及其地质意义

本文分析了小秦岭成矿带金矿化不同矿化类型、石英脉型金矿化不同矿化阶段及不同金矿床类型在垂向上的变化特征,确立了金矿化在垂向上的分带规律。在此基础上,探讨了深部"第二矿化段"存在的可能性,推断了金矿化的剥蚀深度及矿脉在深部的矿化特点,为金矿床的深部预测提供了可靠的依据。     

Exhumation of the Mesozoic Guojialing Granodiorite: Implication for the Preservation of Gold Deposits in the Jiaobei Terrane,China

Preservation conditions are very important for mineral systems and a suitable exhumation process is critical for endogenetic deposits, especially for those deposits formed in orogenic settings, where deposits are inclined to erode away due to strong uplift. The G uojialing batholith, intruding into the L inglong granites and the J iaodong G roup right before regional gold mineralization, is one of the most important gold ore‐hosting M esozoic intrusions in the J iaobei terrane. Gold deposits and the intrusion together underwent similar tectonothermal evolutionary processes. Exhumation and denudation process of the G uojialing granodiorite was constrained by biotite geobarometry and apatite fission track (FT ) analysis. Biotite geobarometric data yields an emplacement depth of 3.0 km, while denudation since 110 M a was calculated from the FT data at about 2.7 km. FT inverse modeling revealed a rapid uplift since ca 100 Ma. Compared with the gold ore‐forming depth which is confined between 2.5 and 9.5 km by fluid inclusion studies, great gold potential in the depths is inferred in the J iaobei terrane. Our result is consistent, to some extent, with the hypothesis of a M esozoic paleoplateau in E ast C hina.     

胶东西北部金矿剥蚀程度及找矿潜力和方向——来自磷灰石裂变径迹热年代学的证据

矿床形成后会经历不同形式的变化,区域隆升与剥蚀是影响矿床变化保存最为关键的因素之一。构造-热年代学是目前广泛运用于研究区域隆升剥蚀的一种重要手段,本文以我国最大金矿集中区———胶东西北部金矿及赋矿围岩玲珑花岗岩为研究对象,尝试将构造-热年代学引用到矿床成矿后变化与保存研究。通过磷灰石裂变径迹热年代学测试获得玲珑花岗岩距今110Ma以来的隆升演化历史,结果显示岩体剥蚀速率很小,平均0.0303±0.0044mm.a-1,自金矿形成后区域热-构造运动趋于平静,这对矿床的保存非常有利。胶东金矿成矿深度范围集中于4~10km,根据剥蚀速度计算玲珑花岗岩剥蚀量仅为2.0~4.2km,远未达到金矿最大成矿深度。当前本区金矿勘探和开采深度普遍小于2km,深部金矿找矿潜力良好。     

从成矿构造动力学探讨脉状金矿床成矿深度

在综述国内外与韧性剪切带有关的脉状金矿床成矿动力学的新近研究成果后,根据成矿控矿构造动力学特征及其与成矿流体运移机制、矿物结晶特点的关系认为矿物结晶发生于地震微破裂导致成矿流体压力骤降后的低压力阶段,由矿物包裹体压力并按静岩压力梯度推算的成矿深度要明显小于矿床的实际成矿深度.本文提出一种新的成矿深度估算方法,其估算的成矿深度与目前大多数脉状金矿床中石英具有明显的韧性变形的特点相吻合.     

矿床形成深度与深部成矿预测

阐述了不同类型内生矿床的成矿深度和金属沉淀的垂直范围。热液成矿作用的深度下限可以下降到10000～12000m。不同类型矿床的成矿深度范围与成矿时的具体地质构造特征有关,且有很大的变化空间。金属矿床的形成深度受成矿母岩岩浆侵位深度的约束,而岩浆侵位的深度又与岩浆中挥发组分的数量、流体释放的时间、成矿元素的矿物/熔体和溶液/熔体分配系数等因素有关。据此可以解释斑岩铜-(钼)、斑岩钼-(铜)和斑岩钨矿床形成深度的差异。地温梯度和多孔岩石的渗透率也与成矿深度有关。CO2等挥发组分的溶解度对压力非常敏感,因此流体包裹体地质压力计对于成矿深度的确定有重要的应用价值。在开展深部成矿预测和找矿时,探寻隐伏岩体顶上带或岩钟是寻找深部与花岗岩有关的多金属矿床的捷径之一。     

矿床形成深度与深部成矿预测

摘要：阐述了不同类型内生矿床的成矿深度和金属沉淀的垂直范围。热液成矿作用的深度下限可以下降到10000～12000m。不同类型矿床的成矿深度范围与成矿时的具体地质构造特征有关,且有很大的变化空间。金属矿床的形成深度受成矿母岩岩浆侵位深度的约束,而岩浆侵位的深度又与岩浆中挥发组分的数量、流体释放的时间、成矿元素的矿物/熔体和溶液/熔体分配系数等因素有关。据此可以解释斑岩铜－（钼）、斑岩钼-(铜)和斑岩钨矿床形成深度的差异。地温梯度和多孔岩石的渗透率也与成矿深度有关。CO2等挥发组分的溶解度对压力非常敏感,因此流体包裹体地质压力计对于成矿深度的确定有重要的应用价值。在开展深部成矿预测和找矿时,探寻隐伏岩体顶上带或岩钟是寻找深部与花岗岩有关的多金属矿床的捷径之一。     

Skarn-greisen deposits of the lost river and mount ear ore field,Seward Peninsula,Alaska, United States

The boron, tin, tungsten, beryllium, and fluorite deposits of the York Range, Seward Peninsula, represent the continuation of the Asian segment of the Pacific ore belt and are globally conjugate with the Verkhoyan-Chukotka ore province of Northeastern Russia. They are localized in the alteration aureoles of dolomites and limestones of the Paleozoic Port Clarence Formation at the contact with the Mesozoic leucocratic granites and genetically belong to the magnesian-skan ore formation. Ore-generating process developed in marbles, skarns, and greisens under hypabyssal conditions in several stages and was accompanied by sequential formation of polymineral assemblages. Early mineralization is represented by magnetite in prograde pyroxene skarns after dolomites. Postmagmatic ore stage is represented by formation of endogenous borates, including their tin-bearing Mg-Fe species, in the magnesian skarns, superposition of calcareousskarn assemblages containing calcium borates, borosilicates, and scheelite, formation of cassiterite and wolrframite in the greisenized granites, and precipitation of sulfides, chrysoberyl, and fluorite. The mineral composition of the rocks and ores was formed under the influence of F-bearing hydrothermal solutions, which caused the presence of fluorine in borates, rock-forming silicates, and the replacement of calcite by fluorite. Boron, tin, beryllium, and fluorine participate at all the stages of endogenous process, but the mineral modes of their occurrence are varied, which is confirmed by data on their chemical composition. The results of studying the skarns and ores of the Alaska deposits are of great applied and scientific significance, and can be used for study of skarn-greisen deposits localized at the contacts of carbonate rocks with granite intrusions of the Pacific ore belt and other world’s regions.     

Complex mineralization at large ore deposits in the Russian Far East

Genetic and mineralogical features of large deposits with complex Sn, W, and Mo mineralization in the Sikhote-Alin and Amur-Khingan metallogenic provinces are considered, as well as those of raremetal, rare earth, and uranium deposits in the Aldan-Stanovoi province. The spatiotemporal, geological, and mineralogical attributes of large deposits are set forth, and their geodynamic settings are determined. These attributes are exemplified in the large Tigriny Sn-W greisen-type deposit. The variation of regional tectonic settings and their spatial superposition are the main factor controlling formation of large deposits. Such a variation gives rise to multiple reactivation of the ore-magmatic system and long-term, multistage formation of deposits. Pulsatory mineralogical zoning with telescoped mineral assemblages related to different stages results in the formation of complex ores. The highest-grade zones of mass discharge of hydrothermal solutions are formed at the deposits. The promising greisen-type mineralization with complex Sn-W-Mo ore is suggested to be an additional source of tungsten and molybdenum. The Tigriny, Pravourminsky, and Arsen’evsky deposits, as well as deposits of the Komsomol’sk and Khingan-Olonoi ore districts are examples. Large and superlarge U, Ta, Nb, Be, and REE deposits are localized in the southeastern Aldan-Stanovoi Shield. The Ulkan and Arbarastakh ore districts attract special attention. The confirmed prospects of new large deposits with Sn, W, Mo, Ta, Nb, Be, REE, and U mineralization in the south of the Russian Far East assure expediency of further geological exploration in this territory.     

Mineralogy and formation conditions of ores in the Bereznyakovskoe ore field,the Southern Urals,Russia

The Bereznyakovskoe ore field is situated in the Birgil’da-Tomino ore district of the East Ural volcanic zone. The ore field comprises several centers of hydrothermal mineralization, including the Central Bereznyakovskoe and Southeastern Bereznyakovskoe deposits, which are characterized in this paper. The disseminated and stringer-disseminated orebodies at these deposits are hosted in Upper Devonian-Lower Carboniferous dacitic-andesitic tuff and are accompanied by quartz-sericite hydrothermal alteration. Three ore stages are recognized: early ore (pyrite); main ore (telluride-base-metal, with enargite, fahlore-telluride, and gold telluride substages); and late ore (galena-sphalerite). The early and the main ore stages covered temperature intervals of 320–380 to 180°C and 280–300 to 170°C, respectively; the ore precipitated from fluids with a predominance of NaCl. The mineral zoning of the ore field is expressed in the following change of prevalent mineral assemblages from the Central Bereznyakovskoe deposit toward the Southeastern Bereznyakovskoe deposit: enargite, tennantite, native tellurium, tellurides, and selenides → tennantite-tetrahedrite, tellurides, and sulfoselenides (galenoclausthalite) → tetrahedrite, tellurides, native gold, galena, and sphalerite. The established trend of mineral assemblages was controlled by a decrease in $ f_{S_2 } $ f_{S_2 } , $ f_{Te_2 } $ f_{Te_2 } and $ f_{O_2 } $ f_{O_2 } and an increase in pH of mineral-forming fluids from early to late assemblages and from the Central Bereznyakovskoe deposit toward the Southeastern Bereznyakovskoe deposit. Thus, the Central Bereznyakovskoe deposit was located in the center of an epithermal high-sulfidation ore-forming system. As follows from widespread enargite and digenite, a high Au/Ag ratio, and Au-Cu specialization of this deposit, it is rather deeply eroded. The ore mineralization at the Southeastern Bereznyakovskoe deposit fits the intermediate- or low-sulfidation type and is distinguished by development of tennantite, a low Au/Ag ratio, and enrichment in base metals against a lowered copper content. In general, the Bereznyakovskoe ore field is a hydrothermal system with a wide spectrum of epithermal mineralization styles.     

江西修水西部金矿成矿地质特征及控矿因素分析

从区域成矿地质背景、矿床特征等方面介绍了修水西部金矿成矿地质特征,并对控矿因素进行分析,认为该矿床属构造蚀变岩型金矿和石英脉型金矿,矿石具有不同的矿化组合特征,应属同一成矿机制作用的产物。     

Nature, origin and evolution of the granitoid-hosted early Proterozoic copper-molybdenum mineralization at Malanjkhand, Central India

At Malanjkhand, Central India, lode-type copper (-molybdenum) mineralization occurs within calcalkaline tonalite-granodiorite plutonic rocks of early Proterozoic age. The bulk of the mineralization occurs in sheeted quartz-sulfide veins, and K-silicate alteration assemblages, defined by alkali feldspar (K-feldspar ≫ albite) + dusty hematite in feldspar ± biotite ± muscovite, are prominent within the ore zone and the adjacent host rock. Weak propylitic alteration, defined by albite + biotite + epidote/zoisite, surrounds the K-silicate alteration zone. The mineralized zone is approximately 2 km in strike length, has a maximum thickness of 200 m and dips 65°–75°, along which low-grade mineralization has been traced up to a depth of about 1 km. The ore reserve has been conservatively estimated to be 92 million tonnes with an average Cu-content of 1.30%. Supergene oxidation, accompanied by limited copper enrichment, is observed down to a depth of 100m or more from the surface. Primary ores consist essentially of chalcopyrite and pyrite with minor magnetite and molybdenite. δ³⁴S (‰) values in pyrite and chalcopyrite (−0.38 to +2.90) fall within the range characteristic of granitoid-hosted copper deposits. δ¹⁸O (‰) values for vein quartz (+ 6.99 to +8.80) suggest exclusive involvement of juvenile water. Annealed fabrics are common in the ore. The sequence of events that led to the present state of hypogene mineralization is suggested to be as follows: fracturing of the host rock, emplacement of barren vein quartz, pronounced wall-rock alteration accompanied by disseminated mineralization and the ultimate stage of intense silicification accompanied by copper mineralization. Fragments of vein quartz and altered wall rocks and striae in the ore suggest post-mineralization deformation. The recrystallization fabric, particularly in chalcopyrite and sphalerite, is a product of dynamic recrystallization associated with the post-mineralization shearing. The petrology of the host rocks, hydrothermal alteration assemblages, ore mineral associations, fluid inclusions and the sulfur and oxygen isotopes of ores are comparable to those in Phanerozoic (and reported Precambrian) porphyry-copper systems, and the Malanjkhand deposit has important implications for both metallogenic models for, and mineral exploration in, Precambrian terrains.     

矿床及其组合是地壳演化的标志物──右江幔隆的发生、发展与滇黔桂卡林型金矿关系探讨

现代金成矿地球动力学的研究，揭示了矿床及其组合与构造变动、岩浆活动一样，是地壳变革的一个事件，因此从成矿环境地质方面可反演矿床及其组合的形成史，正确划分出与区域地壳演化阶段相适应的矿化类型；滇黔桂卡林型金矿的形成与右江幔隆的发生、发展息息相关，本文借用金成矿地球动力学的一些思想，用地幔隆起的观点分析了本区卡林型金矿的形成。     

Ore-magmatic systems and metallogeny of gold and silver in Northeastern Asia

Regional ore-magmatic systems (OMS’s) and metallogenic gold-silver belts in northeastern Asia are considered, with emphasis placed on their relationships owing to the effect of geodynamic settings and underlying and host rock sequences on the localization of gold and silver deposits of different types. Particular types of lithologic assemblages with specific mineralogical and geochemical features are persistent throughout the metallogenic belts, controlled by regional noble-metal OMS’s. Regional OMS’s with one-, two-, and multilevel local OMS’s producing different types of noble-metal mineralization are described. The problem of mineral typomorphism in metallogenic analysis has been first raised. This analysis permits one to recognize indicators of ore formation (a particular genetic type of deposits, their formation and denudation levels), sources of ore-forming fluids, regional specific geochemistry and its relationship with magmatism. Regular presence of platinum in gold-bearing metallogenic zones is shown.     

长江中下游抛刀岭大型中硫型浅成低温热液金矿床的厘定及其找矿启示

长江中下游是全球重要的斑岩-矽卡岩铜多金属矿床成矿带之一,近年来识别出一些大型明矾石矿床、中小规模高硫型和低硫型金±银矿床,但是否存在中硫型矿化蚀变系统还不清楚.抛刀岭是近年来在长江中下游成矿带新发现的大型独立金矿床,文章通过岩芯编录、短波红外光谱和矿物成分的研究,厘定该矿床矿体主要产于～140 Ma英安斑岩脉中,成矿...     

Composition and genesis of the Konevinsky gold deposit,Eastern Sayan,Russia

The Konevinsky gold deposit in southeast Eastern Sayan is distinguished from most known deposits in this region (Zun-Kholba, etc.) by the geological setting and composition of mineralization. To elucidate the cause of the peculiar mineralization, we have studied the composition, formation conditions, and origin of this deposit, which is related to the Ordovician granitoid pluton 445–441 Ma in age cut by intermediate and basic dikes spatially associated with metavolcanic rocks of the Devonian–Carboniferous Ilei Sequence. Four mineral assemblages are recognized: (1) quartz–pyrite–molybdenite, (2) quartz–gold–pyrite, (3) gold–polysulfide, and (4) telluride. Certain indications show that the ore was formed as a result of the superposition of two distinct mineral assemblages differing in age. The first stage dated at ~440 Ma is related to intrusions generating Cu–Mo–Au porphyry mineralization and gold–polysulfide veins. The second stage is controlled by dikes pertaining to the Devonian–Carboniferous volcanic–plutonic association. The second stage is characterized by gain of Hg and Te and formation of gold–mercury–telluride paragenesis.     

The relation between Cu/Au ratio and formation depth of porphyry-style Cu–Au ± Mo deposits

Constraints on gold and copper ore grades in porphyry-style Cu–Au ± Mo deposits are re-examined, with particular emphasis on published fluid pressure and formation depth as indicated by fluid inclusion data and geological reconstruction. Defining an arbitrary subdivision at a molar Cu/Au ratio of 4.0 × 10⁴, copper–gold deposits have a shallower average depth of formation (2.1 km) compared with the average depth of copper–molybdenum deposits (3.7 km), based on assumed lithostatic fluid pressure from microthermometry. The correlation of Cu/Au ratio with depth is primarily influenced by the variations of total Au grade. Despite local mineralogical controls within some ore deposits, the overall Cu/Au ratio of the deposits does not show a significant correlation with the predominant type of Cu–Fe sulfide, i.e., chalcopyrite or bornite. Primary magma source probably contributes to metal endowment on the province scale and in some individual deposits, but does not explain the broad correlation of metal ratios with the pressure of ore formation. By comparison with published experimental and fluid analytical data, the observed correlation of the Cu/Au ratio with fluid pressure can be explained by dominant transport of Cu and Au in a buoyant S-rich vapor, coexisting with minor brine in two-phase magmatic hydrothermal systems. At relatively shallow depth (approximately <3 km), the solubility of both metals decreases rapidly with decreasing density of the ascending vapor plume, forcing both Cu and Au to be coprecipitated. In contrast, magmatic vapor cooling at deeper levels (approximately >3 km) and greater confining pressure is likely to precipitate copper ± molybdenum only, while sulfur-complexed gold remains dissolved in the relatively dense vapor. Upon cooling, this vapor may ultimately contract to a low-salinity epithermal liquid, which can contribute to the formation of epithermal gold deposits several kilometers above the Au-poor porphyry Cu–(Mo) deposit. These findings and interpretations imply that petrographic inspection of fluid inclusion density may be used as an exploration indicator. Low-pressure brine + vapor systems are favorable for coprecipitation of both metals, leading to Au-rich porphyry–copper–gold deposits. Epithermal gold deposits may be associated with such shallow systems, but are likely to derive their ore-forming components from a deeper source, which may include a deeply hidden porphyry–copper ± molybdenum deposit. Exposed high-pressure brine + vapor systems, or stockwork veins containing a single type of intermediate-density inclusions, are more likely to be prospective for porphyry–copper ± molybdenum deposits.     

The Central Aldan gold-uranium ore magmatogenic system,Aldan-Stanovoy shield,Russia

The Central Aldan ore district (CAOD) is considered as an integral ore-forming magmatogenic system (IOMS) consisting of ore-forming systems of different ranks. The epicenter of the IOMS is occupied by the main (head) magma conduit expressed at the present erosion level as the Western El’kon magmatic area. The systematic radial position of the main ore-bearing zones relative to the IOMS’s epicenter is considered as an indication of their relation to the head magma conduit. There are daughter ore forming systems of the first order (the El’kon (EOS), Kuranakh (KOS), and Tommot (TOS)), as well as ore systems of higher orders. Ore zoning distinctly observed in the EOS and KOS and outlined in the TOS consists of the change of the gold or molybdenum (EOS) mineralization for gold-uranium mineralization toward the head of the magma conduit. The ore objects are derivatives of magmatic reservoirs (chambers) located at different levels of the staged magmatogenic system. The gold and uranium mineralization is mainly related to the pervasive potassic metasomatism. The CAOD is considered as a superproductive area promising for revealing new large ore deposits and recommended as a priority object for large scale gold and uranium exploration.     

The stages and duration of formation of gold mineralization at copper-skarn deposits (Altai–Sayan folded area)

Gold mineralization at copper-skarn deposits (Tardanskoe, Murzinskoe, Sinyukhinskoe, Choiskoe) in the Altai–Sayan folded area is related to different hydrothermal-metasomatic formations. It was produced at 400–150 ºC in several stages spanning 5–6 Myr, which determined the diversity of its mineral assemblages. Gold mineralization associated with magnetite bodies is spatially correlated with magnesian and calcareous skarns, whereas gold mineralization in crushing zones and along fault sutures in moderate- and low-temperature hydrothermal-metasomatic rocks (propylites, beresites, serpentinites, and argillizites) is of postskarn formation. Different stages were manifested with different intensities at gold deposits. For example, the Sinyukhinskoe deposit abounds in early high-temperature mineral assemblages; the Choiskoe deposit, in low-temperature ones; and the Tardanskoe and Murzinskoe deposits are rich in both early and late gold minerals. Formation of commercial gold mineralization at different copper-skarn deposits is due to the combination of gold mineralization produced at different stages as a result of formation of intricate igneous complexes (Tannu-Ola, Ust’-Belaya, and Yugala) composed of differentiated rocks from gabbros to granites.