Petrogenesis and Tectonic Significance of Shenxianshui Alkaline Granite in Gejiu,Yunnan Province,China

The Shenxianshui granites in the western Gejiu area were formed in the Late Cretaceous.Laser ablation inductively coupled plasma mass spectrometry indicates zircon U-Pb ages ranging from 90.67±0.7 to 85.97±0.6 Ma.The intrusive rocks are peraluminous(A/CNK=1.03 to 1.33)and calc-alkaline,showing an affinity towards I-type granite.Large ion lithophilic elements are enriched in K and Rb,while high field strength elements are depleted.Moreover,light rare earth elements are significantly enriched,showing a slight negative Eu anomaly(Eu/Eu^(*)=0.39 to 0.58).Shenxianshui granite has a relatively high initial Sr isotope ratio(^(87)Sr/^(86)Sr)_(i)(0.7098-0.7105),negative ε_(Nd)(t)values(−7.99 to−7.44)and negative ε_(Hf)(t)values(−8.37 to−2.58).Combined with previous studies,these characteristics suggest that the Shenxianshui alkaline granites were formed in a post-collision extensional environment.The alkaline granitic magma possibly originated from the partial melting of the lower crust during the Mesoproterozoic era and may have contained mantle source materials.Shenxianshui alkaline granite was formed from mixed magma with a high degree of crystal differentiation.The abundance of ore-forming elements indicates that Shenxianshui granite has the potential to mineralize key metals and rare earth elements.

The Characteristics of Migration of Ore Solutions in No.6 East Tin Deposit of the Songshujiao Orefield, Gejiu

No. 6 East tin deposit in the Songshujiao orefield, Gejiu, is characterized by one-stage hydrothermal activity and monotonous country rocks. The authors selected this deposit and used the multivariate statistical analysis to study the types of association of main ore-forming elements at different temperatures and pressures and their distribution in the deposit. On that basis combined with the structural analysis of the deposit, the recto-geochemical features of No.6 East tin deposit have been revealed and the direction and channel of migration of the ore solutions in faults and the deposit have been deduced. This research can appropriately elucidate the control of faults on the migration of ore solutions and the sites where ore solutions are dispersed and accumulated, thus providing the theoretical basis for the prediction of hydrothermal deposits in question.

A Metallogenic Model of Tecto-Geochemistry on Tin-Polymetal Deposit in Malage Orefield of Gejiu Mining Area

By means of multivariance analysis and finite element on the basis of the analysis of generation andevolution of structural systems and structural system of syn-metallogenesis in the orefield,the authorsmade a research into the interrelation between tecto-geochemistry and structural stress field,revealedthe mechanism of metallogenesis by magma and ore-forming fluids driven under dynamic forces,andproposed a tecto-geochemistry model for the formation of the ore deposits,so as to suggest a basis oftheory for the prognoses of location and magnitude of hidden deposits.

Characteristics of Geochemical Evolution of Trace Elements and REE in Gejiu Granites, Yunnan Province

The evolution characteristics of Gejiu granites.Yunnan Province are described in terms of theirPetrology,especially their trace elements and REE geochemistry The three major types of Gejiu granites:porphyritic biotite monzonitic granite(stageⅠ),medium-coarse-grained biotite-K-feldspar granite(stage Ⅱ)and two-mica alkali-feldspar granite(stage Ⅲ)are thought to have been formed successively from the samegranite magma source through fractional crystallization(Rayliegh fractionation),because linear correlationsare found between log(Rb/Sr)-log Sn,log(Rb/Ba)-log Sn,log(Rb/Ba)-log(Rb/Sr),log La-log Sr,log Ce-log Sr,log Eu-log Sr,etc In addition.the characteristics of REE distribution patterns in these three major types ofgranites also reflect the magmatic differentiation features of Gejiu granites.Of the three major types,the twomica alkali-feldspar granite of stage Ⅲ nuderwent the strongest differentiation,and thus has the closestgenetic relationship with the Gejiu tin-polymetallic ore deposit Such tin-polymetal mineralized granites arecharacterized by high Rb/Sr and Rb/Ba ratios,low K/Rb and ∑Ce/∑Y ratios and remarkable Eu depletion.

HIV/AIDS Related Discrimination in Health Care Service:a Cross-sectional Study in Gejiu City, Yunnan Province

Objectives To investigate discrimination against people living with HIV (PLWH) and its impacts. Methods Forty people who were either HIV positive (7/40) or had high risk behavior (33/40) were interviewed. Focus group discussion was held in the interview with people who were suspected to be infected with HIV, and in-depth interview was conducted in the survey of HIV positive persons whose privacy was strictly protected to ensure the confidentiality of the collected information. Results It was identified that six forms of discrimination against people living with HIV occurred in health care service in Gejiu, including speaking to patients in an insulting manner, refusing to provide health care service, delaying treatment, treating differently, uncovering patients’ privacy, and over-protecting themselves against patients. Discrimination against people living with HIV greatly affected their health conditions. Conclusions Discrimination against people living with HIV in health service has negative impact on their physical and mental health.

Distribution and existing state of indium in the Gejiu Tin polymetallic deposit, Yunnan Province, SW China

The Gejiu tin polymetallic deposit, located in the southwest margin of the South China Belt bordering on the Yangtze Block, is hosted in Triassic carbonates. This study shows that there is an indium enrichment in the ores.Indium mainly exists in sphalerite-rich massive sulfide ores with a concentration of 198.3–1570 ppm; the indium concentration in sphalerite ranges from 493.3 up to4781 ppm. The inferred indium reserve in the Gejiu Sn deposit is over 4000 t, indicating that the Gejiu tin deposit is a giant In-bearing Sn-polymetallic deposit, similar to the Dachang and Dulong in southwest China. Sphalerite with a high Fe value(8.05–13.27 wt%) is the predominant indium carrier mineral; meanwhile chalcopyrite plays the secondary indium carrier role. EPMA mapping result shows that indium is likely distributed homogeneously and presented as a substitution for Zn in sphalerite.

Mineral Geochemical Compositions of Tourmalines and Their Significance in the Gejiu Tin Polymetallic Deposits, Yunnan, China

The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schorl with Fe/ (Fe+Mg) ratios of 0.912-1.00 and Na/(Na+Ca) ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/(Fe+Mg) ratios of 0.212-0.519 and Na/ (Na+Ca) ratios of 0.786-0.997. Tourmalines from the country rocks are dravite with Fe/(Fe+Mg) ratios of 0.313-0.337 and Na/(Na+Ca) ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/(Fe+Mg)=0.374-0.843, Na/(Na+Ca)=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.

Diversity of Mineralization and Spectrum of the Gejiu Superlarge Tin-Copper Polymetallic Deposit,Yunnan,China

The Gejiu (个旧) deposit is a superlarge tin-copper polymetallic ore-forming concentration area characterized by excellent metallogenic geological settings and advantageous ore-controlling factors. The deposit displays diverse mineralization properties due to different minerals and mineral deposit types. Based on the principal metallogenic factors, metallogenic mechanisms, mineralized components, and occurrence of mineral deposits or ore bodies, the Gejiu mineral district can be divided into 2 combinations of metallogenic series, 4 metallogenic series, 8 subseries, and 27 mineral deposit types. Spatial zonality is evident. The distribution regularity of the elements in both plane and section is Be-W, Sn (Cu, Mo, Bi, Be)-Sn, Pb, Ag-Pb, Zn around a granitic intrusion. The metallogenic epoch is mainly concentrated in the late Yanshanian. During this period, large-scale metallogenic processes related to movement caused by tectonics and magmatism occurred, and a series of magmatic hydrothermal deposits formed. The ore-forming processes can be divided into 4 stages: the silicate stage, the oxide stage, the sulphide stage, and the carbonate stage. Based on the orderliness and diversity (in terms of time, space, and genesis) of the mineralization, the authors have developed a comprehensive spectrum of ore deposits in the Gejiu area. This newly proposed diversity of mineralization and the spectrum developed in this work are useful not only for interpreting the genesis of the Gejiu deposit but also for improving mineral exploration in the area, and in particular, for finding large deposits.

Geochronology of the Gabbro-mafic Microgranular Enclaves-granite Associations in the Gejiu District, Yunnan Province and Their Geodynamic Significance

Many igneous rocks distribute in Gejiu tin polymetallic ore-field at Yunnan province, rocks including basalt, gabbro, mafic microgranular enclaves, granites (porphyritic granite and equigranular granite) and akaline rocks. The ages of the granites and akaline rocks which are considered to have genetic connecting with the mineralization have been comfirmed, but the gabbro- mafic microgranular enclaves-granite assemblage's ages are still unknown. By means of LA-ICP-MS zircon U-Pb dating, the data of Shenxianshui equigranular granite, the mafic microgranular enclave in Jiasha area, the host rock of the mafic microgranular enclaves and the Jiasha gabbro are around ~80 Ma. Besides the above mentioned data, a group of new ages at ~30 Ma were discovered in this study, which is from gabbro and mafic microgranular enclaves. Based on the previous data and the new data gained this time, we suggest the major geochronology framework of the magmatism and mineralization events in Gejiu area is ~80 Ma, which is consistent with the Late Cretaceous magmatism and mineralization events in the whole southeast Yunnan and west Guangxi area and they were suggested to belong to the same geotectonic setting in late Yenshannian. And the new ages of the ~30 Ma obtained in this study is considered to represent a responding to the complicate tectonic evolution history of the Tibetan orogenic events in Cenozoic.

Geochemical Characteristics of Rare Earth Elements in Gejiu Tin Polymetallic Deposits, Yunnan Province, China

In order to get a better understanding of metallogeny, the geochemical characteristics of REE and trace element for Gejiu tin polymetallic deposits were studied by comparing concentrations of REE and trace elements in different type ores and rocks, including skarn-type ore, bedded-type ore, vein-type ore, altered granite, country rocks. Results of this study indicated that the metallogenic matters for different type ores in the study area might be derived from the same origin source, which may be mainly related to granitic activities. Furthermore, there are some differences in concentrations of REE in different ores due to their different depositional mechanism during that time. LREE concentrations were enriched relatively in the vein-type ores and the bedded-type ores with relatively low total REE concentrations, whereas total REE concentrations were higher in the skarn-type ores with LREE and HREE concentrations in wide variation ranges.

Helium, lead and sulfur isotope geochemistry of the Gejiu Sn-polymetallic ore deposit and the s ources of ore-forming materials

Studies on the helium, lead and sulfur isotopic composition were performed of the Gejiu super-large Sn-polymetallic ore deposit. The results indicated that the ore-forming materials came from different sources and the deposit is a product of superimposed mineralization. The deposit is characterized by multi-source and multi-period mineralization, which experienced submarine hydrothermal deposition and Late Yanshanian magmatic hydrothermal mineralization. It is held that the Gejiu super-large Sn-polymetallic ore deposit is a multi-genesis deposit.

Relationship among cancer,indoor radon and geology from Gejiu area

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Radon,Lung Cancer Risk and Environmental Geology in Gejiu Area

The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first inthe world. The radon level (indoor, soil) was measured in the Gejiu area by the SSNTDmethod from 1990 to 1996. The result indicates an extensive high-level of indoor radon in thatarea though U and Th are lower in local limestones. The indoor radon level of houses located inthe geologic fault zone is 6 times high that 2 km far from the fau1t zone. The reason probably isthat the radon level of soil in the fault is 6-8 times high that 1 km far from the faults. Ourdata indicate that a lower range of rad0n levels, 0 - 100 Bq’ m- 3, exists in healthy families.However, a higher radon level, over 800 Bq’ m- 3, is often f0und corresponding to that of can-cer patients’ homes (the house-owners are suffering from either lung cancer or leukaemia or liv-er cancer). Obviously, an increase in lung cancer incidence follows an increase in indoor radonlevel. The risk of cancer induced by indoor radon is no longer an inference, but a fact.

云南个旧卡房辉绿岩墙锆石U-Pb年龄、地球化学特征及其岩石圈伸展作用

【研究目的】卡房辉绿岩成因与成岩构造环境的探索对研究个旧地区构造岩浆演化具有重要的科学意义。【研究方法】本文基于LA-ICP-MS锆石U-Pb年龄、全岩地球化学和Sr-Nd-Pb同位素分析等方法研究卡房辉绿岩墙的形成年代、地球化学特征及地质意义。【研究结果】锆石U-Pb地质年代学研究表明卡房辉绿岩侵位年龄为77 Ma,年龄为2409 Ma、2616 Ma、290 Ma的继承锆石指示个旧地区存在新太古代和古元古代构造热事件形成的变质基底以及早二叠世的岩浆活动。卡房辉绿岩属于钾玄岩系列,以低硅、高钾、高钛、高镁为特征,富集Rb、K、Sr等大离子亲石元素,亏损Nb、Ta、Zr、Hf等高场强元素,具有与洋岛玄武岩相似的稀土和微量元素分布特征。卡房辉绿岩具有较高的初始^(87)Sr/^(86)Sr同位素比值(0.70782~0.70791)和正的εNd(t)值(2.07~2.29);初始铅同位素组成中,(^(206)Pb/^(204)Pb)t=18.286~18.465,(^(207)Pb/^(204)Pb)t=15.668~15.717,(208Pb/^(204)Pb)t=37.763~38.830。Sr-Nd-Pb同位素特征指示卡房辉绿岩岩浆源区具有富集地幔(EM2)特征。【结论】卡房辉绿岩成岩机制为在伸展构造背景下,上涌的软流圈地幔底侵富集岩石圈地幔。在岩石圈地幔60~120 km深度,石榴石二辉橄榄岩经过5%~15%的部分熔融,形成了卡房辉绿岩的初始岩浆,在岩浆侵位过程中同化混染下地壳物质并经过较弱的分离结晶作用形成了卡房辉绿岩。

火试金富集-原子吸收光谱法测定冰铜中的金

本文对云锡某铜冶炼厂的3个冰铜样品进行测定,采用硫酸对冰铜试样进行预处理,过滤去除试样中大部分的铜,剩余的残渣灰化后火试金富集得到金银合粒,用稀硝酸溶解银粒,剩于的金粒用王水溶解后,用火焰原子吸收光谱仪在242.8nm处测定金的含量;与行业标准(YS/T 990.2-2014)测定结果比对,其中一个结果在行业标准的检出限以下,另外两个结果基本吻合;同时做了精密度和加标回收试验,结果表明:相对标准偏差(RSD,n=6)在0.54%~1.13%之间,加标回收率在96.0%~104%。

Identification of the Ore-Forming Anomaly Component by MSVD Combined with PCA from Element Concentrations in Fracture Zones of the Laochang Ore Field,Gejiu,SW China

Fault and fractures are well-developed in the Gejiu tin-polymetallic district,and they are closely related to the formation and distribution of ores.In this paper,the principal component analysis(PCA)and multifractal singular value decomposition(MSVD)methodologies were applied for identification of the ore-forming anomaly components from element concentrations of fault rocks in the Laochang ore field,Gejiu.The results show that:(1)the wall rocks and fault rocks have anomalous concentrations of ore-forming elements,indicating that these elements are mainly derived from fluid/rock interaction in the fracture zones;(2)PCA based on clr-transformed data was used to recognize significant association anomalies of ore-forming elements,which lay a foundation for further extracting ore-forming anomaly components from the element association anomalies related to Sn-Cu mineralization;(3)MSVD could effectively explore local anomaly features and decompose ore-forming element association anomalies associated with buried mineralization in more detail.The ore-forming element anomaly components can delineate ore-finding Sn-Cu polymetallic deposits more exactly than the ore-forming element association anomalies.

云南个旧锡矿区区域人体重金属暴露研究

本文采集了个旧锡矿区附近个旧、蒙自和开远三个城市随机人体后枕部头发样品100件,测试As,Cd,Cr,Pb,Hg,Cu,Zn七种重金属全量,并与其他矿区人发重金属含量对比分析。结果表明,人发中As元素超标率最高;Cu,Pb,Zn,Cd和Cr含量几何均值空间分布距离矿区越近均值越大的特点;As、Pb和Cd之间呈显著正相关,性别和年龄在人发中七种重金属的积累贡献较小;个旧矿区区域成人和儿童的致癌风险均超标,且成人风险大于儿童,非致癌风险也均超标,儿童风险大于成人;人体健康评价对比结果表明,As、Zn和Hg致癌风险最大,需引起重视。

滇东南个旧矿区花岗岩黑云母成分特征及其对锡成矿的指示

滇东南个旧矿区发育有著名的超大型锡多金属矿床,该矿床的形成与花岗质岩浆活动密切相关。本文利用电子探针分析技术对个旧矿区花岗岩中的黑云母开展研究;研究结果表明,黑云母表现出富铝铁、贫镁钙的特征,其FeO^(T)含量为22.81%~26.17%,含铁指数为0.75~0.81,属于富铁黑云母。黑云母的化学组成特征显示其具有较高的结晶温度(616℃~691℃)、结晶压力(318~403 MPa)和结晶深度(12.03~15.24 km),以及较低的氧逸度(logf_(O_(2))=-19.74~-17.05)。综合研究表明,个旧矿区花岗岩源区物质复杂,具有多源性;花岗岩中黑云母整体表现出高铁指数和较低氧逸度等特征,是锡成矿的有利条件。

云南个旧芦塘坝—阿西寨地区深部矿化的浅部表征:构造蚀变与原生晕指示

层间氧化矿是个旧高松矿田重要的锡矿化类型。加强该类型矿化的研究与勘探工作有望成为缓解老矿山资源危机、提升矿产储量的有效手段之一。本文选择具有层间氧化矿良好成矿条件的芦塘坝—阿西寨地区为研究区,开展地表构造蚀变和原生晕地球化学研究,为该地区层间氧化矿的勘查提供新的依据。野外地质调查表明,研究区地表矿化蚀变明显受断裂控制,特别是NE向断裂与EW向断裂交汇部位蚀变强烈,主要由铁泥质蚀变和方解石脉构成。蚀变岩及围岩中13种关键元素组合分析揭示Cd、As、Sb、Pb和Zn对寻找Sn矿体有良好的指示意义。根据地表原生晕地球化学综合异常分布,结合构造蚀变带特征,圈定出Ⅰ至Ⅳ4个成矿靶区。通过对比分析各靶区原生晕的前缘晕、近矿晕和尾晕的元素组合特征,推测Ⅰ和Ⅱ号靶区深部层间氧化矿找矿潜力较好;Ⅲ号靶区地表氧化矿已被剥蚀,但深部有可能存在硫化矿;Ⅳ号靶区深部可能有少量剩余的未被剥蚀的氧化Sn矿体。