含辉钼矿全岩样品Re-Os同位素定年研究:在北京大庄科钼矿床中的应用

采用硝酸在比色管中对辉钼矿样品中Re含量进行初测的方法,测得辉钼矿标准样品JDC Re含量与推荐值在误差范围内基本一致,与传统的Carius管法相比,该方法具有简便快速的特点。传统的辉钼矿Re-Os同位素定年分析对象为辉钼矿单矿物,根据所测得的187Re/187Os值获得辉钼矿的Re-Os年龄,Re、Os在辉钼矿中大量富集,而在硅酸盐矿物中几乎没有,探索性地对含有辉钼矿的全岩样品进行Re-Os同位素定年,虽然所得Re、Os含量偏低,但187Re/187Os值不会变。该方法省去了选样过程花费的大量时间,避免了选样过程中可能造成的交叉污染。采用同位素稀释Carius管逆王水法探索性地对北京大庄科钼矿床中含辉钼矿全岩样品进行Re-Os同位素年龄测定,获得了(137.6±3.7)Ma精确的等时线年龄,与挑选出辉钼矿单矿物样品的Re-Os同位素等时线年龄(136.8±2.6)Ma吻合较好,直接厘定了大庄科钼矿的成矿时代。该年龄与矿区汉家川石英二长岩锆石U-Pb年龄一致,表明大庄科钼矿的形成与汉家川石英二长岩关系较为密切,为中国东部第二期大规模成矿作用的产物,形成于中国东部岩石圈伸展环境。     

力马河镍矿Re-Os同位素研究

四川力马河镍矿是峨眉山大火成岩省一个重要的岩浆硫化物矿床。本文通过对其主要岩、矿石类型Re、Os及其同位素组成的分析,综合探讨了成矿岩体原始岩浆性质、矿石硫化物成因、成矿机制及Re-Os同位素等时线年龄。结果表明,力马河镍矿不同类型岩矿石样品初始Os同位素组成是不均一的,富硫化物的网脉状矿石及其选纯硫化物Os同位素组成初值差异较小,其等时线年龄为265±35 Ma、与岩体锆石SHRIMP年龄263±3 Ma基本相当;硫化物含量较低的岩、矿石样品间初始Os同位素组成差异较大,其表观等时线年龄大于成矿年龄。分析认为,岩矿样品初始Os同位素组成的不均一是由含较高放射成因187Os丰度的硫化物熔体和含较低放射成因187Os丰度的硅酸盐熔体不同比例混合造成的。混合模型分析表明,硫化物含量超过30％的矿石样品初始187Os/188Os基本接近,硫化物含量低于30％的岩矿石样品初始187Os/188Os随硫化物含量上的不同差异很大,为岩浆硫化物矿床Re-Os等时线年龄可能出现多组年龄解的现象提供了一种可能的解释。成矿岩体中含放射成因187Os丰度最低的岩石样品γOs（t=260Ma）在5左右、Cu/Pd比值在7000左右,表明是基本没有受到地壳混染及硫化物熔离影响的原始岩浆结晶分异产物,估计原始岩浆Os含量在1×10－9左右,为苦橄质岩浆。矿石硫化物Re/Os比值显著高于任何赋矿橄榄岩,γOs（t=260Ma）高达110左右,综合分析揭示了力马河镍矿硫化物为二次熔离成因,模式分析认为,矿石硫化物是由原始岩浆经历R=2000左右的硫化物熔离后、其亏损岩浆再经R=200左右的硫化物熔离形成,与二次熔离相对应,成矿岩浆也经历了两次混染作用,分别为上、下地壳7％左右的混染。     

Re-Os同位素体系在金属矿床中的应用

Re-Os同位素体系已成为金属矿床定年和示踪的重要手段之一。文章在简述Re-Os同位素体系基本原理基础上,综述了国内外的最新研究成果,认为Re-Os同位素测试对象不再局限于辉钼矿和铜镍硫化物矿石,黄铁矿、毒砂、磁黄铁矿、镍黄铁矿、闪锌矿等也常作为测试对象用于金矿床、铅锌矿床、沉积喷流型钴(金)等矿床的定年。地壳岩石与原始地幔相比,具有较高的187 Os/188 Os比值、γOs值以及Re/Os比值,因此,硫化物或矿石的Re-Os同位素组成和普通Os—Re/Os比值图解可以揭示斑岩矿床、金矿、铅锌矿以及铜镍硫化物矿的成矿物质来源。辉钼矿则可以通过Re含量来示踪成矿物质来源。Re-Os同位素也可与其他同位素结合(如187 Os/188 Os-87Sr/86Sr)共同判明不同端元组分对成矿的贡献。     

湖南鲁塘石墨矿Re-Os同位素研究

石墨具有较高的Re、Os含量,可望成为理想的Re-Os同位素测年对象,但迄今国内外研究较少,尤其在煤层经变质作用形成石墨过程中,其中Re-Os同位素体系的变化还有待研究。湖南鲁塘石墨矿是我国典型的隐晶质石墨矿床之一,矿体产于二叠系龙潭组煤系地层中。本文采用Carius管逆王水溶解样品,直接蒸馏、微蒸馏分离纯化Os,丙酮萃取法分离富集Re,热表面电离质谱法对鲁塘矿区石墨样品以及外围原煤进行了Re-Os同位素分析。结果表明:鲁塘石墨的Re含量为0.901~9.794 ng/g,Os含量为7.3~189.5 pg/g,Re-Os同位素等时线年龄为155.6±3.6 Ma,该年龄与鲁塘石墨矿东侧骑田岭岩体第二阶段中粒黑云母花岗岩锆石U-Pb年龄153~157 Ma一致,表明了龙潭组煤层受到骑田岭岩体"烘烤"作用,发生热接触变质作用,使得靠近骑田岭岩体原煤变质为石墨,形成石墨矿床。通过对比石墨、原煤和骑田岭岩体Re、Os含量及比值,发现石墨中的Re、Os主要来源于原煤,并根据石墨Re-Os等时线初始(187Os/188Os)i值(0.686±0.032),推测骑田岭岩体在侵入煤系地层过程中,有少量具有较低187Os/188Os值的Os被碳质吸附。     

Re-Os同位素测年法在油气成藏年代学的研究进展

铼—锇(Re-Os)同位素应用于油气成藏年代学是近10年来的一个前沿领域,在国际上已取得了重要成果,目前国内对此方法的应用还较缺乏。利用Re-Os同位素测年法开展页岩或沥青等富有机质沉积岩的研究,可以精确厘定油气运移和充注时间,也可以有效示踪烃源岩。在阅读国内外大量文献的基础上,概述了Re-Os同位素定年原理,分析了海水—沉积物中Re和Os元素的富集过程,总结了Re-Os同位素测年的测试对象、样品准备和分析测试方法。指出初始187Os/188Os比值不仅可以限定油气生成和油气充注的年龄,还可以有效评价源—油关系;放射成因的187Os/188Os比值与烃源岩年龄呈正相关。认为烃类成熟度、生物降解作用和水洗作用不足以造成Re-Os等时线图中出现离散点,而初始187Os/188Os比值变化、沉积后Re和Os的流动性和硫酸盐热化学还原作用是引起Re-Os等时线图中出现离散点的3个主要原因。Re-Os年龄的重现性和准确性与样品颗粒的大小及取样量密切相关。相对于其他同位素测年法,Re-Os同位素测年法的最大优势在于对直接参与油气成藏的地质体进行研究,可以得到油气成藏期的直接证据。最后探讨了现阶段ReOs同位素体系研究中尚存在的问题,就未来研究热点和发展方向做出展望,以期能有效推动Re-Os同位素定年相关的理论和技术的深入发展。     

辉钼矿Re-Os同位素定年方法的改进与应用

公认的Re-Os同位素定年代表物辉钼矿,目前已在金属硫化物矿床年代学研究领域获得了广泛的应用。本研究采用浓HNO₃分解辉钼矿样品,大大地简化了Re和Os的化学制备过程,并根据辉钼矿中正常Os含量水平相对放射成因¹⁸⁷Os可以忽略的特点,以正常Os标准为稀释剂,实现了仪器测量过程中Os同位素质量分馏的在线校正,改善了分析数据的质量。该方法经辉钼矿国家标准物质进行验证,获得了满意的Re、Os含量及Re-Os年龄数据,并且在南岭地区与连阳复式岩体相关的姓坪夕卡岩型钼矿床成矿年龄研究中获得了成功应用。在实际应用中,为了获得有意义的能反映真实地质事件的年龄数据,辉钼矿样品不仅要有足够的取样量,而且还要保证粒度细、混合均匀。     

石灰岩铼-锇同位素分析方法研究及应用初探

针对石灰岩样品Re-Os同位素分析,在选样和溶样方法上进行了改进,在Carius管封闭前加入HCl与石灰岩反应释放出大量CO2,然后加入氧化剂和稀释剂封闭Carius管溶解样品,大大增加了样品取样量。利用改进的方法对采自青海玉树地区二叠世九十道班组底部的灰黑色微细晶灰岩的Re-Os同位素体系进行了分析测定,得到了精确的沉积年龄(283.1±7.1)Ma(MSWD=0.61,Model1,n=7)。187Os/188Os同位素初始值为0.56±0.12,与二叠纪时海水的187Os/188Os值相一致,反映了石灰岩沉积时海水的187Os/188Os比值。所得石灰岩年龄与其中的生物化石年龄相吻合,并且与区域上岩浆岩锆石年龄相互印证,表明Re-Os同位素体系在该石灰岩中的封闭性较好。通过石灰岩中有机碳含量以及其中Re、Os含量关系研究,得出了Re、Os在灰岩中主要赋存于有机质中的结论。从原理上解释了Re-Os同位素体系在灰岩中的应用具有十分广泛的前景。     

石墨Re-Os同位素分析及其在成矿年代学中的初步运用

本文探索性地对江西省铅山县长寿源铅锌共生的晶质石墨进行了Re-Os同位素分析。研究结果显示石墨的Re-Os同位素年龄为424±25Ma(n=7,MSWD=7.8),与该区二云二长花岗岩中锆石的年龄(433±9Ma)在误差范围内相一致,说明石墨的成因与区域上岩浆的侵入存在密切联系。Re的含量介于47×10-9～330×10-9之间,普通Os和187Os的含量分别为0.32×10-9～2.15×10-9和0.27×10-9～1.75×10-9,相对于Re、Os在地壳中的丰度显著富集,Os同位素初始比值187Os/188Os=1.69±0.29,表明石墨来源于富有机质沉积地层。通过测定石墨样品中的有机碳和固定碳,对Re、Os在石墨中的赋存状态进行了研究,表明Re、Os可能是以某种形式赋存在石墨的固定碳中,与其中有机质无关。从原理上解释了石墨的Re-Os同位素年龄反映的是使沉积地层中的炭质变质为石墨,并发生富集迁移的岩浆热变质事件的时期。研究表明石墨的Re-Os同位素分析技术不仅能够为变质作用时间的精确测定提供新的方法,而且对矿床成因的研究也具有重要意义。     

浙江长兴“金钉子”灰岩Re Os富集机制研究

通过对浙江长兴煤山D剖面二叠—三叠"金钉子"灰岩样品Re-Os同位素、主微量元素和有机碳测定,对不同层位灰岩的沉积环境进行了判别。通过分析灰岩主微量元素、有机碳与Re、Os含量的相关性,探索性地研究了灰岩中Re、Os富集机制。研究发现,灰岩中Re、Os的富集主要受氧化还原作用影响,Re只有在还原环境下,才会被灰岩中的有机物富集,此时灰岩中Re含量较高,适用于Re-Os同位素定年,而Re在氧化环境下很难被灰岩中有机质富集。Os在还原环境下同样被有机质富集,但氧化环境下,部分Os也可以被灰岩地层中含铁、铜等自生矿物吸附富集,含铁、铜等自生矿物Os同位素比值可以代表沉积时海水Os同位素特征。Re、Os在灰岩中的富集机制研究对于将Re-Os同位素应用于灰岩地层精确定年及古环境示踪具有重要意义。Re、Os在不同氧化还原条件下的富集差异导致了还原环境沉积的灰岩中187 Re/188 Os要大于氧化环境灰岩中187 Re/188 Os,灰岩中187 Re/188 Os变化对研究古海洋沉积氧化还原环境可能具有一定指示意义。     

苏皖地区幔源橄榄岩捕瞄虏体的锇同位素组成、模式年龄及其意义

苏皖地区发育的新生代玄武岩中富含地幔橄榄岩捕虏体，测定了25个橄榄岩全岩的锇同位素组成。结果表明大部分样品呈亏损特征,187Os/188Os=0.119～0.129.Os同位素比值与主量成分之间有显著的相关性.采用187Os/188Os-Al2O3代用等时线方法,由截距得到初始值(187Os/188Os)0=0.109,在对流地幔的187Os/188Os比值演化线上获得模式年龄t=2.5(±0.1)Ga,为晚太古-早元古代。用样品组中最低的锇同位素组成,即187Os/188Os=0.119,计算Re亏损模式年龄,t=1.2Ga,为中元古代。表明苏皖地区新生代玄武岩中的地幔橄榄岩捕虏体具有古老的形成年龄,它们是经过显生宙减薄作用后的残余地幔的碎片。大陆岩石圈地幔的古老形成年龄与上覆地壳克拉通的古老稳定年龄相耦合。     

Subgrain-scale decoupling of Re and Os and assessment of laser ablation ICP-MS spot dating in molybdenite

Reproducibility of Re-Os molybdenite ages depends on sample size and homogeneity, suggesting that Re and Os are decoupled within individual molybdenite crystals and do not remain spatially linked over time. In order to investigate the Re-Os systematics of molybdenite at the subgrain (micron) scale, we report LA-ICP-MS Re-Os ages for an Archean molybdenite crystal from Aittojärvi, Finland, analyzed in situ in a white aplite matrix. A related Aittojärvi molybdenite (A996D), in the form of a very fine-grained mineral separate, is used as one of our in-house NTIMS standards, and thus its age of 2760 ± 9 Ma is well established. Measurements of (¹⁸⁷Re + ¹⁸⁷Os)/¹⁸⁵Re on micron scale spots along 200 μm traverses across the crystal yield a wide range of ages demonstrating that, in this case, microsampling of molybdenite does not produce geologically meaningful ages. Experimentation with mineral separations and sample size over a 7-yr period predicted that this would be the outcome. We suggest that ¹⁸⁷Os is more likely to be the mobile species, based on its charge and ionic radius, and that ¹⁸⁷Os becomes decoupled from parent ¹⁸⁷Re with time on the micron and larger scale. Incompatible charge and ionic radius for Os ions formed during reduction of molybdenite-forming fluids may explain the widely observed absence of common (initial) Os in molybdenite. Geologically accurate ages for molybdenite can only be obtained for fully homogenized crystals (or crystal aggregates) so that any post-crystallization ¹⁸⁷Re-¹⁸⁷Os decoupling is overcome.A growing number of geologically accurate ID-NTIMS ¹⁸⁷Re-¹⁸⁷Os ages for homogenized molybdenite suggest that postcrystallization mobility of radiogenic ¹⁸⁷Os must be limited to within the molybdenite mineral phase. We suggest that radiogenic ¹⁸⁷Os may be stored in micron scale dislocations, kink bands, and delamination cracks produced by deformation, and that the unusual structure and deformation response of molybdenite results in an increased chemical stability in this mineral. Migration of ¹⁸⁷Os into adjacent silicate phases is highly unlikely, but other contacting sulfides may take in Os. In an example from a Proterozoic skarn deposit at Pitkäranta (western Russia), we demonstrate minor loss of radiogenic ¹⁸⁷Os from molybdenite and a corresponding gain in adjacent chalcopyrite such that the molybdenite age is not perceptibly disturbed, whereas the resulting chalcopyrite ages are impossibly old. Therefore, it is unadvisable to perform Re-Os analytical work on any sulfide in contact or intimate association with molybdenite. In addition to large errors in the age, if the isochron method is employed, initial ¹⁸⁷Os/¹⁸⁸Os ratios could be erroneously high, leading to seriously errant genetic interpretations.     

Macroscale NTIMS and microscale LA-MC-ICP-MS Re-Os isotopic analysis of molybdenite: Testing spatial restrictions for reliable Re-Os age determinations, and implications for the decoupling of Re and Os within molybdenite

We present a detailed study of Re-Os age determinations for eight natural molybdenite samples of like polytype (2H), spanning a range of age, natural grain size and deposit type. The focus of the study is to critically evaluate the effects of sampling, sample preparation and aliquant size on the accuracy and reproducibility of Re-Os ages for these molybdenite samples. We find that for some molybdenite samples, analysis of small sample aliquants (<20 mg) may not yield accurate or reproducible Re-Os ages, whereas analysis of larger aliquants from the same mineral separate do yield reproducible Re-Os dates. Such an observation is best explained if Re and ¹⁸⁷Os are internally decoupled within molybdenite grains. This finding is supported from spot analyses by laser ablation MC-ICP-MS analyses presented here and is consistent with previously published observations.The degree of decoupling between Re and ¹⁸⁷Os appears to increase both as a function of increasing grain size, and increasing age of molybdenite. From detailed dating of individual molybdenite mineral separates, we provide approximate minimum aliquant amounts required for reproducible Re-Os age dating, as a function of molybdenite age and grain size. Geologically younger, naturally fine-grained molybdenite samples appear to show little Re and ¹⁸⁷Os decoupling, and reproducible ages can be determined from some samples with as little as 1 mg of aliquant. Geologically old, and coarse-grained molybdenite samples may require as much as 40 mg of aliquant from a much larger mineral separate to overcome Re and ¹⁸⁷Os decoupling. The mechanism(s) of Re and ¹⁸⁷Os decoupling within molybdenite is not constrained by this results of this study, but the observation that the degree of decoupling increases with grain size (distance) and age (time/geologic history) may suggest primary diffusive control. Assuming that Re and ¹⁸⁷Os decoupling in molybdenite results primarily from diffusion of ¹⁸⁷Os, apparent diffusion coefficients are calculated (D = x²/t). Estimates of D for Os made in this way range from 2.8 × 10⁻²⁶ to 2.1 × 10⁻²¹ m²/s, which are broadly similar to experimentally derived diffusion coefficients for Os in Fe-sulfide minerals and for Re in molybdenite at temperatures <500°C.     

半封闭硝酸溶解体系ICP-MS快速测定辉钼矿的Re-Os年龄及Re含量

Re-Os法能够直接厘定内生金属矿床成矿时代,但是封闭Carius管法化学流程复杂,且有一定的危险性。本文建立了一种简便快速测定辉钼矿Re-Os年龄及其Re含量的方法。用3 mL浓硝酸在10 mL比色管中溶解5~15 mg辉钼矿样品,将溶液中的钼酸沉淀分离后稀释定容,直接采用质谱测量187和185质量数比值(M187/M185)。利用辉钼矿Re-Os年龄标准物质JDC和HLP的M187/M185值与其年龄的正相关线性关系计算未知辉钼矿样品的Re-Os年龄,并通过¹⁸⁵Re计数利用相对法计算Re含量。本方法应用于测量13.26~2130 Ma的辉钼矿,Re-Os年龄的测定值与推荐值的相对偏差多数在0.36%~7.42%之间,由于放射性积累较多,长年龄样品测量的准确度较高。与传统Carius管法相比,该方法不需要加入稀释剂,省去了封闭和打开Carius管环节以及Re-Os分离纯化流程,适合于辉钼矿Re-Os年龄的初步分析。     

Sources of unique rhenium enrichment in fumaroles and sulphides at Kudryavy volcano

Rhenium (Re) is one of the least abundant elements in Earth, averaging 0.28 ppb in the primitive mantle. The unique occurrence of rheniite ReS₂ (74.5 wt% of Re) in Kudryavy volcano precipitates raises questions about recycling of Re-rich reservoirs within the Kurile-Kamchatka volcanic Island arc setting. The sources of this unique Re enrichment have been inferred from studies of Re-Os isotope systematic and trace elements in volcanic gases, sulphide precipitates and host volcanic rocks. The fumarolic gas condensates are enriched in hydrophile trace elements relative to fluid-immobile elements and exhibit high Ba/Nb (133-204), Rb/Y (16-406) and Th/Zr (0.01-0.25) ratios. They are characterised by high Re (7-210 ppb) and Os abundances (0.4-0.9 ppb), with ¹⁸⁷Os/¹⁸⁸Os ratios in a range 0.122-0.152. This Os isotopic compositional range is similar to that of the peridotite xenoliths from the metasomatised mantle wedge above the subducted Pacific plate, the radiogenic isotopic signature of which is probably due to radiogenic addition from a slab-derived fluid.Re- and Os-rich sulphide and oxide minerals precipitate from volcanic gases within fumarolic fields. Molybdenite (MoS₂), powellite (CaMoO₄) and cannizzarite (Pb₄Bi₆S₁₃) contain 1.5-1.7 wt%, 10 ppm, and 65-252 ppb of Re, respectively. Both molybdenite and rheniite contain normal Os concentrations, with total Os abundances in a range from 0.6 to 3.1 ppm for molybdenite, and 2.3-24.3 ppb for the rheniite samples. Repeated analyses of osmium isotope ratios for two rheniite samples form a best-fit line with an initial ¹⁸⁷Os/¹⁸⁸Os ratio of 0.32 ± 0.15 and an age of 79 ± 11 yr, which is the youngest age ever measured in natural samples. The high Re contents in molybdenite and rheniite led to high radiogenic ¹⁸⁷Os values, even in the limited period of time, with ¹⁸⁷Os/¹⁸⁸Os ratios up to 3.3 for molybdenite and up to 4.4 for rheniite.The Os isotopic compositions of andesite-basaltic rocks from the Kudryavy volcano (¹⁸⁷Os/¹⁸⁸Os up to 0.326) are more radiogenic than those of residual peridotites and fumarolic gas condensates that are mainly constituted from magmatic vapor. Such radiogenic values can be attributed either to the addition of a radiogenic Os-rich subduction component to the depleted mantle, or to the assimilation of older dacitic caldera walls (¹⁸⁷Os/¹⁸⁸Os = 0.6) during arc magma ascent and emplacement. The latter hypothesis is supported by the correlation between ¹⁸⁷Os/¹⁸⁸Os ratio and indicators of fractionation such as MgO or Ni, and by low contents of potentially hydrophile trace elements such as Ba, Rb and Th relative to fluid-immobile elements such as Nb, Zr and Y. The high Re flux in the Kudryavy volcano (estimated at ∼46 kg/yr) can be explained by remobilisation of Re by Cl-rich water from an underplated mantle wedge and subducted organic-rich sediments of the Pacific plate.     

Re-Os elemental and isotopic systematics in crude oils

Analysis of 12 worldwide oil samples show that Re and Os abundances are positively correlated with the asphaltene content of oil. Light oils with <1% asphaltene content have basically no measurable Re or Os. Within oil, Re and Os are present dominantly in the asphaltene fraction (>83%), with <14% Re and Os found in the maltene fraction, this distribution is similar to other trace metals such as V and Mo. Rhenium and Os could be present in oil as metalloporphyrin complexes, but given their abundance in the asphaltene component they are also likely bound by heteroatomic ligands. The ¹⁸⁷Re/¹⁸⁸Os and ¹⁸⁷Os/¹⁸⁸Os values in asphaltene calculated at the estimated time of oil generation (Os_i) are similar to those of the whole oil, as expected from the elemental results. This suggests that the asphaltene fraction can be used to approximate the Re-Os isotopic compositions of the whole oil. Os isotopic compositions in oils show a considerable range, from ¹⁸⁷Os/¹⁸⁸Os of 1.9-6.0, and they correlate positively with the age of the proposed source rock. Re/Os ratios also show a large range and overlap the Re/Os ratios found in typical oil source rocks such as organic rich shale.     

Sulfides in mantle peridotites from Penghu Islands, Taiwan: Melt percolation, PGE fractionation, and the lithospheric evolution of the South China block

Major elements, highly siderophile elements (HSE) and Re-Os isotope ratios were analysed in situ on individual sulfide grains in spinel peridotite xenoliths hosted by Miocene intraplate basalts from the Penghu Islands, Taiwan. The xenoliths represent texturally and compositionally different mantle domains, and the geochemical characteristics of the sulfides show changes in HSE distribution and Re-Os isotope systematics, produced as their host rocks were metasomatised by percolating fluids/melts. In prophyroclastic and partly metasomatised peridotites from the Kueipi (KP) locality, the sulfides have subchondritic to superchondritic ¹⁸⁷Re/¹⁸⁸Os and ¹⁸⁷Os/¹⁸⁸Os ratios. Many of these sulfides reflect fluid/melt interaction with residual MSS and/or crystallization of fractionated sulfide melts, which produced high contents of Cu and PPGEs and high Re/Os; inferred melt/rock ratios are low. In contrast, sulfides in equigranular and extensively metasomatised peridotites from the Tungchiyu (TCY) locality are mainly more sulfur-rich Ni-(Co)-rich MSS, with subchondritic to chondritic ¹⁸⁷Os/¹⁸⁸Os and subchondritic ¹⁸⁷Re/¹⁸⁸Os. These sulfides are interpreted as products of interaction between pre-existing MSS and percolating silicate melts. Melt/rock ratios were high and the percolating melt was less differentiated than the melt that percolated the KP peridotites. Sulfides in a TCY pyroxenite are mainly MSS; they have the lowest HSE contents, subchondritic to superchondritic ¹⁸⁷Os/¹⁸⁸Os and subchondritic ¹⁸⁷Re/¹⁸⁸Os, and may have precipitated from sulfide melts that segregated from basaltic melts under S-saturated conditions. In most sulfides melt percolation appears to have induced fractionation among the HSEs and disturbed Re-Os isotope compositions. Despite the metasomatic effects, rare residual MSS, sulfides that from crystallised sulfide melts and sulfides modified by addition of Re (with no evidence for Os addition) can still provide useful chronological information. Such sulfides yield T_RD age peaks of 1.9, 1.7-1.6, 1.4-1.3 and 0.9-0.8 Ga, which may record the timing of melt extraction and/or metasomatic events in the mantle. These periods are contemporaneous with the major crustal events recorded by U-Pb dates and Nd and Hf model ages in the overlying crust. This close correspondence indicates that the sulfide T_RD ages reflect the timing of lithosphere-scale tectonothermal events (such as melting and metasomatism) that affected both the lithospheric mantle and the overlying crust. The sulfide T_RD ages, taken together with the crustal data, suggest that most of the Cathaysia block had formed at least by Paleo-Proterozoic time, and that some domains are Archean in age.