Microporous gold is common in many Te-Au deposits. Experimental formation and textures of microporous gold have recently been studied. However, few studies have worked on naturally occurring microporous gold. At the Dongping gold deposit, which is one of the most studied Au-Ag-Te deposits in China natural microporous gold is widely distributed in both primary and oxidized ores. This provides a good opportunity to study the textures and the formation of microporous gold in nature. This gold is pseudomorphous in addition to being porous, indicating that it formed via interface coupled dissolution-reprecipitation (ICDR) reactions. Four textures that were not described previously in experiments were observed in samples from this deposit. (1) A hackly interface between the microporous gold and parent calaverite. Te content shows a decreasing trend with increasing distance from the interface. This texture may result from diffusion of excess surface energy as the ICDR reaction moves towards equilibrium. (2) A less-porous band exists in the microporous gold. The band has fewer pores, smaller crystal sizes and similar chemical composition with the surrounding microporous gold. It likely formed due to the fluctuation of the fluid physicochemical conditions (including decreasing temperature, alpha(O2(aq)) and increasing pH) that changes the dissolution rate of calaverite. (3) Microporous gold precipitated between quartz and calaverite. As well, gaps developed between gold and remnant calaverite. This texture is derived from catalytic effects of a heterogeneous nucleation or recrystallization process. It is helpful for extraction and aqueous processing of Au-Te ores, and accounts for the phenomenon that quartz can accumulate gold in some hydrothermal gold deposits. (4) Petzite coexists with Ag-bearing microporous gold, indicating that petzite may also decompose to microporous gold under hydrothermal conditions.Calaverite could be dissolved without altered pyrite at high-temperature (> 200 degrees C) conditions, but under weathering conditions, pyrite would be altered first. In primary ores, microporous gold coexists with pyrite and baryte, indicating that it was formed during the late-stage mineralization. In oxidized ores, microporous gold coexists with limonite and baryte, indicating it may have generated during late-stage mineralization and then altered by weathering. Hydrothermal fluids derive from late-stage mineralization may play the main role in the formation of microporous gold compared to weathering processes. This observation also leads us to reappraise the importance of hydrothermal fluids in the weathering dominated ICDR geological processes.

南秦岭大型钡成矿带,钡矿物种类丰富。通过对南秦岭钡成矿带钡矿床中矿石和矿化围岩的电子探针研究,结合前人研究成果,发现南秦岭大型钡成矿带中钡主要以重晶石、毒重石、钡解石、菱钡镁石、钡长石、汉江石、安康矿、钡冰长石、钒云母等形式存在;硫化物以黄铁矿为主,并含有少量的针镍矿、闪锌矿、硫钒铜矿、蓝辉铜矿、斑铜矿。此外,还发现少量钒钛氧化物。在研究钡矿物化学组成的基础上,对毒重石、钡解石、菱钡镁石、钡长石、钡冰长石等钡矿物的成因进行了探讨。

The Lianzigou deposit, which has an Au-Te paragenetic association, is hosted in plagioclase gneiss of the Qincanggou Formation in the Taihua Group in the Xiaoqinling region, central China. This quartz vein-type Au deposit comprises native Au and a variety of tellurides. The latter include calaverite (AuTe2), krennerite (Au3AgTe8), petzite (Au3AgTe2), hessite (Ag2Te), melonite (NiTe2), and altaite (PbTe). Four stages have been recognized in this deposit: stage I consists of K-feldspar and quartz; stage II is of milky quartz veins accompanied by coarse-grained disseminated and lumps of pyrite with weak Au mineralization; stage III is composed mainly of Au, tellurides, and sulfides; and stage IV is characterized by abundant carbonate and quartz. Based on mineral assemblage and thermodynamic data, we estimated the physicochemical conditions of the main metallogenic stages. Based on thermodynamic modelling, the physicochemical conditions of Au-Ag-Te mineral associations were estimated. The Au-Ag-Te minerals from stage III formed mainly under conditions of logfO(2) = -43.15 to -33.31, logfH(2)S = similar to-9.29, pH < 7, logfTe(2) = -10.6 to -9.8 and log alpha Au+/alpha Ag+ = -7.2 to -6.5. In contrast, the physicochemical conditions of stage II were higher, specifically pH (8.3-8.5) and logfO(2) (-34.90-31.96). In the ore-forming fluids of the Lianzigou deposit, the dominant Au species was Au(HS)(2)(-) while the dominant Te species were HTe- (aq) and Te-2(2-) (aq). Moreover, the Au-Ag-Te metal associations in the Lianzigou Au deposit were derived from mantle materials related to lithospheric thinning of the eastern North China craton in the Early Cretaceous under an extensional tectonic system.

The Jinqu Au deposit is located in the central Xiaoqinling gold field along the southern margin of the North China Craton. Ore-bearing auriferous quartz veins in the deposit are controlled by E-W trending structures within amphibolite facies metamorphic rocks of the Archean Taihua Group. The ore-forming process in this deposit can be divided into four stages represented by feldspar-quartz, pyrite-quartz, polymetallic sulfide-quartz, and carbonate-quartz veins and veinlets. Here we present fluid inclusion and isotopic data of the Jinqu Au deposit. Four types of fluid inclusions in quartz and calcite are identified, including carbonic-aqueous inclusions (type-1), aqueous inclusions (type-2), solid-bearing inclusions (type-3) and pure carbonic inclusions (type-4) varieties, based on petrography and laser Raman spectroscopy. Quartz in stage I contains type-1 fluid inclusions (FIs) which homogenized to aqueous or carbonic phase at temperature 361 to 406 degrees C and 385 to 400 degrees C respectively, and have salinities of 10.3 to 17.9 wt% NaCl equiv. Type-2 FIs show homogenization temperatures of 347 to 410 degrees C into the liquid phase, with high salinities of 11.6 to 18.6 wt% NaCl equiv. Quartz in stage II is the major host of type-1 FIs, with minor type-4 FIs, the former showing homogenization at temperatures of 305 to 390 degrees C into the carbonic phase and 280 to 410 degrees C into the aqueous phase, with variable salinities of 4.5 to 19.8 wt% NaCl equiv. The stage III quartz contains all the four types of FIs (homogenizing to carbonic or aqueous phase at temperature 309 to 360 degrees C and 295 to 400 degrees C, with salinities of 6.6 to 19.9 wt% NaCl equiv for type-1, and homogenizing to liquid at temperature 308 to 326 degrees C with salinities of 12.5 to 13.2 wt% for type-2 FIs). In stage IV, type-2 FIs are the major type in quartz and calcite with total homogenization temperatures of 213 to 280 degrees C into the liquid phase and variable salinities of 5.3 to 18.6 wt% NaCl equiv. Our data show that the ore-forming fluids of the Jinqu Au deposit are generally characterized by moderate to high homogenization temperatures and variable salinities, belonging to the CO2-H2O-NaCl +/- CH4 system. Based on fluid inclusion data, we infer that fluid immiscibility occurred in stages II and III, and the estimated trapping pressures for stages II and III fluids are between 81 and 275 MPa.The C-H-O isotopic values of fluids (delta O-18(water) = 1.2 to 6.4 parts per thousand; delta DV-SMOW = 68.5 to 56.0 parts per thousand; delta C-13(CO2) = 12.4 to - 3.4 parts per thousand) in stage I to IV and delta C-13(V-PDB) values for calcite (delta C-13(V-PDB) = - 7.6 to - 4.3 parts per thousand) in stage IV suggest that the ore-forming fluids were composed of a mixture of metamorphic water and mantle-derived fluids with minor involvement of meteoric water. Fluid inclusions in pyrite of stage II and III yield He-3/He-4 ratios of 0.88 to 1.39 Ra, and considerable Ar-40/Ar-36 ratios range from 2287.6 to 5669.9, suggesting the mixing of mantle and crustal components. The delta S-34(V-CDT) values of sulfide samples in stages II and III range from - 5.8 to 4.5 parts per thousand (except for a pyrite grain within calcite that shows - 28.5 parts per thousand). The values of Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 of pyrite samples in stages II and III are from 16.919 to 17.321, 15.340 to 15.539, and 37.303 to 37.971 respectively. Our data suggest that the Taihua Group was possibly a major source for the ore-forming metals of the Jinqu Au deposit. Integrating the data from ore geology, fluid inclusions, isotope geochemistry and regional setting, we propose that the Jinqu Au deposit is an orogenic-type deposit which formed within the continental collision setting of the North China and Yangtze Cratons.

The Xiqianluzi Pb-Zn polymetallic deposit is located in the southeast of the southern Beishan belt, whereas the ore-forming metal sources are still unclear. Its Pb-Zn ore bodies mainly occur in the Changcheng system Qianluzigou Group metamorphic clastic rocks, showing zonation of Cu-Zn-Pb metals from deep to surface. The ore structures are mainly banded, massive and veined, which have the characteristics of syngenetic sedimentation. Au mineralization in silty slate is obviously controlled by WNW-ESE-trending faults, and occurs as veined or lenticular type. The Pb, Zn, Cu, and Au are mainly enriched in quartz or siliceous veins. The biotite granodiorites are enriched in Si, Na, Rb, Ba and K, with A/CNK values less than 1.1, and depleted in Nb, P, Ti. They belong to calc-alkalic series and weak peraluminous I-type granite, formed in a post-collision extensional environment and characterized by crust-mantle mixed source. The sulphide minerals in the Pb-Zn ores have delta S-34 values in the range of 17.7 parts per thousand-21.0 parts per thousand with average of 19.2 parts per thousand, reflecting seawater sulphate origin of sulphur. The sulphur of Pb-Zn ores was likely transformed from S6+ to S2- by thermochemical sulphate reduction. The Pb isotopic compositions of sulphide minerals in the Pb-Zn ores have Pb-206/Pb-204 ratios of 16.837-17.001, Pb-207/Pb-204 ratios of 15.437-15.557, and Pb-208/Pb-204 ratios of 36.377-36.889. In contrast, sulphide minerals in Au ores have delta S-34 values (5.4 parts per thousand-7.6 parts per thousand, with average of 6.5 parts per thousand) lower than those of sulphide minerals in the Pb-Zn ores. The delta S-34 values of sulphide minerals in the Au ores are consistent with those of sulphide minerals in the Late Permian-Middle Triassic magmatic hydrothermal gold deposits in the southern Beishan belt, which imply a magmatic source for sulphur. Sulphide minerals in the Au ores have higher lead isotopic ratios, including Pb-206/Pb-204 of 18.249-18.325, Pb-207/Pb-204 of 15.583-15.598, and Pb-208/Pb-204 of 38.023-38.366, compared to those in the Pb-Zn ores. Geological and isotopic features indicate that the Xiqianluzi Pb-Zn polymetallic deposit comprises two mineralization types; namely, its Pb-Zn ores can be considered as Mesoproterozoic sedimentary exhalative type, while its Au ores are magmatic origin. These show that Au mineralization was closely related to the magmatic hydrothermal activities, and thus Au ores can be classified as Late Permian-Early Triassic magmatic hydrothermal Au mineralization.

The Dabaiyang deposit is a typical Te-Au deposit hosted in Archean metamorphic rock in the Zhangjiakou district, northern margin of the North China Craton. It is located close to the famous Dongping Te-Au deposit; however, few researches have performed on the Archean metamorphic rock hosted Te-Au deposits, which precludes the studies on enrichment processes and mechanisms of Te-Au deposits in the Zhangjiakou district. In this contribution, four mineralization stages have been recognized in the Dabaiyang deposit: (1) K-feldspar-quartz veins; (2) quartz-pyrite veins; (3) polymetallic sulfide-quartz veins; and (4) calcite and quartz veins. Metallic minerals in this deposit include pyrite, chalcopyrite, galena, sphalerite, bornite, altaite, hessite, petzite, tetradymite, tellurobismuthite, native gold and electrum, and most of them were precipitated in stage III. Petrography, fluid inclusion microthermometry, and laser Raman spectroscopy revealed that the ore-forming fluid was a medium temperature H₂O-NaCl hydrothermal system. Fluid temperatures evolved from 264–337 °C to 233–323 °C to 209–268 °C to 130–245 °C, and salinities varied from 1.2 to 10.3 wt% to 1.2–8.8 wt% to 4.3–10.5 wt% to 3.8–8.3 wt% NaCl equivalent. Ore-forming fluids yield H and O isotope compositions of −2.4‰ to 4.9‰ and −101.2‰ to −75.5‰, respectively, and ³He/⁴He and ⁴⁰Ar/³⁶Ar ratios of 1.31–1.58 and 3489.0–21824.1, respectively. The hydrothermal fluids were derived initially from magmatic water (stage I), but more mixture of magmatic and meteoric water or heated meteoric water was added to the system (stages II and III), and significant water-rock exchange with the Sanggan metamorphic rock happened during evolution. Calculated physicochemical conditions of ore mineral formation shows that pH decreased, logfO₂ and logfS₂ did not change significantly from the early to the late stage; logfTe₂ and logαAu⁺_(aq)/αAg⁺_(aq) values of stage III are −10.7 to −9.8 and −6.8, respectively. Ore-forming fluid did not suffer boiling during evolution, but mixing with low-temperature meteoric water and water-rock reaction were the dominant mechanisms that led to the precipitation of sulfides, tellurides and Au–Ag minerals in the deposit. The Dabaiyang Te-Au deposit is an epithermal gold deposit and its various hydrothermal fluid sources compared with intrusion hosted Te-Au deposits led to their differences in Te and Au contents, hydrothermal systems and mineral deposition mechanisms.
© 2020 Elsevier B.V.

河北省张家口-宣化地区（张宣地区）位于华北克拉通北缘中段,区内自显生宙以来构造活动频繁,并产出大量岩浆岩和金矿床,是研究华北克拉通北缘岩浆-构造-成矿演化体系的重要对象。本文通过对张宣地区的水泉沟正长岩、响水沟似斑状花岗岩、井儿洼粗安岩-英安岩、象山花岗闪长岩、青羊沟黑云母二长花岗岩和张家口组流纹岩的锆石年龄、Lu-Hf同位素和地球化学组成进行研究,结合前人研究成果,获得区内古生代-中生代岩浆岩的侵位时期主要为海西期（峰值398Ma和373Ma）、印支期（峰值234Ma）和燕山期（峰值143Ma和130Ma）。张宣地区在古生代-中生代经历了古亚洲洋俯冲、华北克拉通破坏及古太平洋俯冲过程。早古生代时期,古亚洲洋向华北克拉通俯冲;到泥盆纪,白乃庙岛弧带和华北克拉通北缘发生弧陆碰撞,张宣地区处于弧陆碰撞后的伸展环境,富集地幔岩浆上涌并经历了地壳的同化混染和分离结晶的共同作用,形成大量碱性岩;二叠纪末期-三叠纪,各微陆块相互碰撞,张宣地区处于碰撞后伸展阶段,地幔岩浆引起加厚下地壳的部分熔融,基性、酸性岩浆混合,导致区内的基性岩与酸性岩共存;侏罗纪-白垩纪时期,华北克拉通发生减薄,形成区内大范围的侵入岩和火山岩。张宣地区产有大量金矿、铅锌矿、银矿及少量铜矿和钼矿,金矿集中产于宣化-崇礼-赤城交界处,而银铅锌多金属矿则成群成带环绕金矿化集中区分布。成矿时间主要为海西期和燕山期,印支期成矿尚未明确,但成矿潜力巨大。根据地质特征和同位素组成,可将张宣地区的金矿床划分为"东坪式"、"小营盘式"和"张全庄式"三类。古生代-中生代各时期岩浆活动对金成矿均有贡献,大部分金矿床与海西期和燕山期岩浆活动联系密切,多期次成矿及成矿叠加是形成张宣地区大量金矿床的重要因素。

低熔点亲铜元素(LMCE)As、Sb、Bi、Hg、Pb、Se、Te、Tl、Sn等,均具有亲铜性、低熔点、半金属的特性,在成矿过程中可以形成LMCE熔体,并对Au、Ag、PGE等贵金属的高效富集沉淀起到一种重要的桥梁作用。作者对前人研究资料与LMCE热力学相