Dating of the Dachang Superlarge Tin-polymetallic Deposit in Guangxi and Its Implication for the Genesis of the No. 100 Orebody

The Dachang superlarge Sn-polymetal deposit in Guangxi, China, is one of the largest tin deposit all over the world. However, this deposit has long been in debate as to its origin. One of the opinions is that the Dachang deposit was formed by replacement of hydrothermal solution originating from Yanshanian granites, and the other is that this deposit was formed by submarine exhalation in the Devonian. This paper presents some new isotopic geochronology data obtained with the 40Ar-39Ar method for quartz and sanidine from massive ore in the No. 91 and No. 100 orebodies. Analytic results show that the No. 91 orebody was formed at 94.52±0.33 Ma (the plateau age obtained with the 40Ar-39Ar method for quartz) or 91.4±2.9 Ma (the plateau age obtained with the 40Ar-39Ar method for feldspar), while the No. 100 orebody was formed at 94.56±0.45 Ma (the plateau age obtained with the 40Ar-39Ar method for quartz), suggesting that both the No. 91 and the No. 100 orebodies were formed at the Late Yanshanian instead of the Devonian. The No. 100 orebody might be formed by filling of ore materials into caves in Devonian reef limestone. Because the ore-bearing solution released its pressure and lowered its temperature suddenly in a cave environment, ore minerals were formed concentratedly while water and other materials such as CO2 evaporated quickly, resulting less alteration of host rocks.

Re–Os dating of molybdenite and in-situ Pb isotopes of sulfides from the Lamo Zn–Cu deposit in the Dachang tin-polymetallic ore field, Guangxi, China

The Dachang tin-polymetallic district, Guangxi,China, is one of the largest tin ore fields in the world. Both cassiterite-sulfide and Zn–Cu skarn mineralization are hosted in the Mid-Upper Devonian carbonate-rich sediments adjacent to the underlying Cretaceous Longxianggai granite(91–97 Ma). The Lamo Zn–Cu deposit is a typical skarn deposit in the district and occurs at the contact zone between the Upper Devonian limestone and the granite.The ore minerals mainly consist of sphalerite, arsenopyrite,pyrrhotite, galena, chalcopyrite, and minor molybdenite.However, the age of mineralization and source of the metals are not well constrained. In this study, we use the molybdenite Re–Os dating method and in-situ Pb isotopes of sulfides from the Lamo deposit for the first time in order to directly determine the age of mineralization and the tracing source of metals. Six molybdenite samples yielded a more accurate Re–Os isochron age of 90.0 ± 1.1 Ma(MSWD = 0.72), which is much younger than the reported garnet Sm–Nd isochron age of 95 ± 11 Ma and quartz fluid inclusions Rb–Sr isochron age of 99 ± 6 Ma. This age is also interpreted as the age of Zn–Cu skarn mineralization in the Dachang district. Further, in this study we found that in-situ Pb isotopes of sulfides from the Lamo deposit and feldspars in the district's biotite granite and granitic porphyry dikes have a narrow range and an overlap of Pb isotopic compositions(^(206) Pb/^(204) Pb =18.417–18.594,^(207) Pb/^(204) Pb = 15.641–15.746, and^(208) Pb/^(204) Pb = 38.791–39.073), suggesting that the metals were mainly sourced from Cretaceous granitic magma.

Finite element modeling of pore-fluid flow in the Dachang ore district,Guangxi,China:Implications for hydrothermal mineralization

Convective heat transfer associated with the circulation of porefluid in porous rocks and fractures within the upper crust of the Earth is substantial when the temperature gradient is sufficiently high. In order to understand the process of Snpolymetallic mineralization in the Dachang ore district of Guangxi, a finite element method has been used in this study to simulate both pore-fluid flow and heat transfer in this district. On the basis of related geological, tectonic and geophysical constraints, a computational model was established. It enables a computational simulation and sensitivity analysis to be carried out for investigating ore-forming pore-fluid flow and other key factors that may affect hydrothermal ore genesis in the district. The related simulation results have indicated that： （1） permeable fault zones in the Dacbang ore district can serve as preferential pathways for pore-fluid flow on a regional-scale; and （2） the pore-fluid flow can affect the salinity distribution. This latter factor is part of the reason why Sn-polymetallic mineralization has taken place in this district.

A Geochemical Study of Rare Earth and Trace Elements in Cassiterite from Dachang Sn-Polymetallic Ore Field,Guangxi Province

Rare earth and trace elements are determined for cassiterite from a vein-type orebody , a lens and a sheeted-type orebody in the Dachang Sn-polymetallic ore field ,Guangxi Province .Cassiterite from the vein-type orebody has rare earth and trace dement characteristics similar to that of Dachang biotite granite of Late Yanshan age, showing an inheritable and a genetic relationship. Cassiterites from the kns and sheeted-vein orebody have rare earth and trace element characteristics greatly different from those of the vein-type cassiterite and the granite,showing distinctly higher contents of the ore-forming elements As, Sb,Zn,Ag etc.and a positive Eu anomaly and a negative Ce anomaly.The difference of rare earth and trace element characteristics for cassiterite from two kinds of orebodies reflects the compositional difference of ore-forming solutions. Authors suggest that the kns and sheeted-vein orebody was of nonmagmatic , mixed with underground hot brine origin , and that this kind of hot brine reacted with Devonian and Predevonian older strata and extraced some ore-forming metals from the strata and finaly empbced along the bedding and interbyer fracture zone etc. on its ascending way driven by the Indonisian orogenic movement . The vein-type orebody was formed chiefly by post-magmatic hydrothermal sobtions derived from magma differentiation of the Dachang biotite granite .

METALLOGENIC SYSTEM OF DACHANG TIN- POLYMETALLIC ORE FIELD

The Dachang tin polymetallic ore field in northern Guangxi, China, lies in a mid late Paleozoic rift that borders up the southern boundary of the Jiangnan Xuefeng Massif. As a giant ore deposit, it deposited in middle of the Nandang Hechi metallogenic zone. The ore hosting strata are of the Devonion, which shows the evident characteristics of polymetallic elements, i.e., Sn, Zn, Pb, Sb, As, Cu, Ag, In, Ge, Cd, et al., and over 1 000 000 t tin reserves.

Geological characteristics and metallogenic significance of the Devonian intermediate-basic volcanic rocks in the Dachang deposit, Guangxi Zhuang Autonomous Region

Recently discovered intermediate-basic volcanic rocks in the Devonian strata at Dachang, Guangxi Zhuang Autonomous Region are dominated by basalts and andesites. Most of them belong to the calc-alkali and alkali series. Petrology and geochemistry data indicate that the volcanic rocks may be formed in a continental rift environment. The volcanic rocks are in conformable contact with the overlying and underlying wall rocks, with such typical sedimentary structures as laminated and striped ones, and the host rocks of the volcanic rocks contain lots of marine fossils such as tentaculite. Many pieces of evidence indicate that the eruption environment of the volcanic rocks is a sea-facies one. The volcanic rocks are of the LREE-enrichment type, with high ratios of light rare-earth elements to heavy rare-earth elements. In addition, they display moderately negative δEu anomalies and moderately negative δCe anomalies with a higher degree of LREE and HREE fractionation. Through the Q-cluster analysis of the REE samples, it is indicated that the ores have a closer relation with the layered volcanic rocks, and also possess a certain inheritance-consistency relationship with the layered volcanic rocks. The source of ore-forming materials may be related with volcanism. It is proposed that the ore deposit in the study area should be genetically explained as the result of marine volcano-sedimentary exhalation of hot water and late superposition-reworking.

Authigenetic K-feldspars and Their Relations to Sn-polymetallic Mineralization in the Dachang Ore Field

Sn-polymetallic ores at Dachang,Guangxi Autonomous Region,China,are hosted in Middle-Upper Devonian reef limestones,siliceous rocks,banded and lenticular limestones,etc.Two types of orebodies can be distinguished according to their telations to the bedding:one is distributed along the bedding and the.other cuts across the bedding.Sn and sulfide orebodies associated with K-feldspare are mostly characterized by laminated ore structure. Microscopic examinations of K-feldspar-bearing rocks,in conjunction with X-ray diffraction,chemical composiion and cathodoluminescence data for K-feldspars,as well as their telations to mineralization,the authors consider that the K-feldspare are of authigenic origin,subordinate to the epigenetic stage of diagenesis,They resulted from the reaction of mixed,deep-seated,circulating underground hot waters rich in K,Al and Si with argillaceous carbonates during the Indo nesian orogenic movement.It is suggested more attention should be paid to the effect of authigenic K-feldspars on Sn mineralization.In the meantime the event related to circulating underground hot waters should also be taken into account so as to provide new clues to blind ore prospecting.

Statistical Analysis of the Hole Primary Halo in Dachang Sn-Zn Polymetallic Mining Area of Guangxi

The complexity and diversity of Ore forming is the commonness,of which the difficulty is the evolutional characteristics of geochemical elements.The metallogetic process can be speculated and get useful and microcosmic message for next exploration.In this paper,the research of cluster analysis and factor analysis of the hole primary halo in Dachang Sn-Zn polymetallic mining area in Guangxi reveal that metallogenic process is very complex and superposed by mineralization.It is considered that the enrichment of Zn,Sn superposed anaphase.By sulphide polymetallic,Au is very independency and that Sb,Pb,Ag and Cu are proximal indicator elements for exploring Zn,Sn in the mine.

Mineral occurrence for Dachang gold deposit and its impact on gold recovery rate in Qumarleb County,Qinghai

Based on X-ray diffraction,optical microscopy and scanning electron microscopy analysis of the Dachang gold ore,it is showed that the sulfide of ore is the main carrier minerals of gold. A majority of gold is embedded in pyrite and tetrahedrite as the form of inclusion and a small amount intergrowth with pyrite and gangue mineral,occasionally the presence is in form of monomer natural gold. The main factors which influence the recovery rate are sulfide mineral particle size,and the fine grained sulfide is beneficial for the dissociation and flotation of gold bearing minerals. The monomer dissociation degree of gold bearing minerals can reach91. 3%,when the grinding fineness is less than 0. 074 mm and grain level accounts as 80%. It is not conducive to the flotation of sulfide if the grinding fineness is low or high. It is difficult to completely dissociate the monomer if there is a small amount of pyrite and arsenopyrite in the ore. Therefore,before leaching the gold,it must conduct pretreatment to reach the ideal recovery rate of the gold,like roasting oxidation,pressure oxidation and biological oxidation. The fine microscopic gold has little influence on the gold recovery rate.

Mantle contributions to granitoids associated with Sn mineralization:Geochemical and isotopic evidence from the giant Dachang deposit,South China

Major Sn deposits are commonly linked to crust-derived and highly evolved granites,with magma generation aided by mantle heating.However,whether and how the mantle components contribute to Sn polymetallic mineralization remains unclear.In this study,in combination with a compilation of equivalent data in the region,we provide new constraints on this issue based on detailed investigations on the petrogenesis and metallogenic significance of granitoids including the causative batholith and later granodiorite porphyry dike in the giant Dachang Sn deposit from South China.The former has zircon U-Pb ages of 93-91 Ma and belongs to highly evolved S-type biotite granite,which experienced fractionation of massive feldspar.The latter shows zircon U-Pb ages of 90 Ma and displays I-type granite features.The batholith was mainly derived from the dehydration melting of biotite in the metasedimentary sources,as revealed by the relatively low whole-rock Pb contents(<30 ppm)and high Ba/Pb ratios(2.71-17.1)and initial T(ti-zr)of 790℃.Compared with the adjacent crust-derived S-type granites(-24.8--5.1)and I-type granites(-11.0 to-5.2),the Dachang S-type biotite granites present higher zirconεHf(t)values(-9.1 to-2.1).Furthermore,the low magmatic zirconδ18O values(6.2‰)and higher apatite LREE(3277-4114 ppm)and Sr(1137-1357 ppm)contents than of arc-type basic rocks were discerned.These characteristics jointly hint the contributions of mantle components.The higher initial T(ti-zr)(>850℃),whole-rock Mg#(52 to 58),apatiteεNd(t)(-9.2 to-6.5)and zirconεHf(t)(-7.6 to 2.5)values but lower zirconδ18O values(6.33 to 8.30‰)of the later granodiorite porphyry dike than those of the batholith also suggest that mantle material was involved in the generation of the dikes,which is evident by the variational features of zircon and apatite trace elements.In addition,at the zircon Hf<12000 ppm and Eu/Eu*>0.05,the higher zirconΔFMQ values(mostly from-1.8 to 2.0)and H2O contents(100-1100 ppm)of the Dachang granitoids than the pure crust-derived S-type granites(ΔFMQ=mostly from-3.7 to-1.5;H2O<100 ppm)imply that mantle materials involved are relatively rich in water and oxidized.These suggest that the addition of mantle components is conducive to the extraction of Sn from metasedimentary sources,and moderately facilitates the increase of oxygen fugacity which still maintains the incompatibility of Sn in magmas withΔFMQ<2.Also,the involvement of mantle components upgrades the H2O contents in S-type magmas,favoring the migration of ore-forming elements from magmas to hydrothermal fluids.The sediment-derived causative granites displayed higherεHf(t)andεNd(t)values with greater Sn tonnages of their associated world-class Sn polymetallic deposits,supporting the opinion that the contributions of mantle components play an important role in the generation of giant Sn deposits.

广西大厂矿田100号锡多金属矿体石英阴极发光与微量元素特征及其对成矿过程的指示

广西大厂矿田100号锡多金属矿体赋存于中泥盆统生物礁灰岩中,其品位高(Sn 1.9%、Sb 5.78%、Zn 12.4%、Pb 6.55%、Ag 235 g/t)、规模大(矿石量超过1300万吨),是广西大厂锡多金属矿田中非常重要的矿床。本文分析了该矿体中石英的阴极发光(CL)特征、流体包裹体组合及微量元素含量,探讨该巨型特富矿体的成矿过程。矿体成矿过程可划分为成矿前(Q1a石英及稍晚的Q1b石英+细粒方解石)、锡成矿(Q2石英+锡石+毒砂+黄铁矿)、锌铅锑成矿(Q3石英+闪锌矿+磁黄铁矿+脆硫锑铅矿)和成矿后(Q4石英+方解石+白铁矿细脉)四个阶段。Q1a石英CL发浅蓝绿‒蓝紫色光,发育生长环带,含临界均一的流体包裹体,其Al含量为48~265μg/g;Q1b石英CL发淡紫色光,CL结构复杂,显示破裂‒溶解‒再沉淀特征,含有不混溶流体包裹体组合,其Al含量为942~4357μg/g;Q2石英CL发淡蓝紫色光,发育生长环带,与其共生的锡石含有不混溶流体包裹体组合,其Al含量为159~1768μg/g;Q3石英CL发棕褐色光,CL结构均一,含有不混溶流体包裹体组合,其Al含量为53~122μg/g;Q4石英CL不发光,含有低气液比(~15%)水溶液流体包裹体,其Al含量低于检测限(<50μg/g)。Q1a石英发育的临界均一的流体包裹体可能代表深部超临界岩浆流体的出溶。矿体深部最近发现的砂岩角砾及Q1b石英破碎的CL结构和不混溶流体包裹体组合表明成矿前超临界岩浆流体在深部发生了隐爆。Al含量从Q1a石英到Q1b石英急剧上升可能与隐爆引起的晶体生长速率加快有关。而Al含量从Q1b石英到Q2石英到Q3石英逐渐降低暗示了持续的流体不混溶过程中酸性气体(CO_(2)、HCl)的逸失及礁灰岩消耗了流体的H+,导致流体pH值逐渐升高,该过程对锡石及硫化物的沉淀起到了促进作用。Q4石英中发育的低气液比水溶液流体包裹体可能代表成矿后大气降水的加入。

Origin of ore-forming fluids of the Dachang Sn-polymetallic ore deposit: Evidence from helium isotopes

The ore genesis model for the Dachang Sn-polymetallic ore deposit has long been in dispute, and the major debate focuses on whether the stratiform and massive orebodies formed during the Yanshanian magmatic-hydro-thermal event or they were products of Devonian syn-sedi-mentary exhalative-hydrothermal event. This note presents new helium isotope data from fluid inclusions of four pyrites and one fluorite. The pyrites were collected from the stratiform and massive orebodies in the deposit, and their 3He/4He ratios are significantly higher than 1, ranging from 1.7 to 2.5 Ra, which indicates a mantle component in the responsible hydrothermal fluids. It is suggested that the ore-forming fluids were a mixture of deep circulating seawater and a mantle-derived fluid, which are similar to many of those modern submarine hydrothermal fluids. In contrast, the fluorite, collected from a granite-related hydrothermal vein in the deposit, shows a low 3He/4He ratio of 0.7 Ra, which indicates no mantle component

基于“肺合大肠”理论探讨流感病毒与肠屏障损伤相关性

现代医学理论中肺与大肠在分化发育、生理病理、功能协作、物质联系上有结构、功能、菌群基础作为支撑依据,这与《黄帝内经》藏象篇中脏腑相关理论不谋而合。在外感热病的疾病传变中,肺与大肠相关联以及反馈调节机制的“肺病从肠论治”“肠病从肺论治”论述成为近年来的研究热点。基于此,从肠屏障的角度系统归纳总结梳理近年来国内外学者探求流感病毒诱导肺系疾病的作用机制,并通过阐述肺经药以及肺肠同治验方作为工具药验证以肺-肠表里理论为指导的药物对流感病毒诱导的肺系疾病的保护机制,揭示流感病毒中肺与肠在疾病传变中的反馈及药物干预机制,阐明肺-肠表里理论的现代内涵,以期为中医药在病毒性疾病中广谱治疗提供现代依据。

Low-temperature geochemical characteristics of ore-forming fluid in the Dachang Sb deposit, Qinglong, Guizhou Province, China

THE samples were collected from the Dachang, Gulu, Xishe and Houpo prospects of the deposit and theminerals for fluid inclusion studies include stibnite and its associated minerals quartz, fluorite, barite,pyrite, calcite, etc. Based on systematical studies by the authors, the data have been obtained on theshape, size and vapor/liquid ratio of 615 fluid inclusions, the homogenization temperatures of 176 fluidinclusions, the salinities of 49 fluid inclusions, the decrepitation temperatures of 20 fluid inclusions, thechemical composition of 8 fluid inclusions and the hydrogen and oxygen isotopic composition of 3 fluid inclusions. On the basis of the above data, this note discusses the low-temperature geochemical characteristics of the Dachang deposit.

广西大厂锡多金属矿田成矿物质来源的示踪

广西大厂锡多金属矿田目前是世界上最大的锡多金属产地之一。为了探讨大厂矿田中铜坑-长坡矿床和高峰矿床成矿物质来源,本研究对这2个矿床主要成矿阶段硫化物的S同位素及主、微量元素进行了分析。研究结果表明,铜坑-长坡硫化物δ^(34)S范围为-9.2‰~0.6‰(均值为-3.3‰),总体呈塔式集中分布于-4‰~-1‰,指示S主要为岩浆和地层混合来源。高峰矿床硫化物δ^(34)S范围为4.2‰~12.1‰(均值为9.7‰),集中分布于10‰~12‰,由于硫酸盐热化学还原作用导致的硫同位素分馏有限,因此,本文推测高峰矿床硫主要来源于海水硫酸盐的还原和岩浆硫的混合。闪锌矿的Zn/Cd值表明,铜坑-长坡和高峰矿床的Zn/Cd值极为相似,并且与矿田地层和大厂花岗岩Zn/Cd值存在重叠,表明铜坑-长坡和高峰矿床硫化物成矿物质(S和金属)主要来源于泥盆系地层和岩浆岩。

宋儒程大昌的学术地位及评价

程大昌为南宋官历三朝的经世名儒,一生勤精治学,著述丰厚。当时及后世对其学术地位评价极高。一是程氏以当世名儒与重臣双重身份在传播儒学及其经世致用等方面弥补了新安理学家治学中所欠缺的践履工夫,成为新安理学的“先哲”;二是程氏肆力为学,博通二典,着力于儒道互补,成为会通儒道的“桥梁”;三是程氏勤政务实,政绩丰硕,被时人誉为国之宝臣,学之准的,成为学术与人格的“典范”。程氏既能在学术上着力于会通儒道,又能将此种会通精神贯彻于政治践履上,甚为当时及后世所赞誉。

大厂凹陷MIS3阶段以来沉积物地球化学特征分析

深海氧同位素3-1阶段是指深海沉积物有孔虫氧同位素记录的第四纪末次冰期至冰后期的一个时期,期间气候表现为间冰阶、极端寒冷、多次千年尺度气候事件至最后转暖多个变化特征,相关气候变化沉积响应及影响因素等科学问题一直以来备受关注。然而,该时期相关千年尺度气候事件的记录及讨论在华北平原地区仍有争议,为探讨华北平原西北地区在该阶段的气候特征,大厂凹陷区天然剖面进行高密度碳14断代样品测试,并开展常量和微量元素地球化学含量分析,获得地球化学数据变化趋势特征,结果表明,该剖面年代从32.5 ka至8.2 ka,处于深海氧同位素3阶段末期至深海氧同位素1阶段早期。在该时段,主量元素氧化物TFe_(2)O_(3)、Al_(2)O_(3)、SiO_(2)、MgO、CaO、Na_(2)O与K_(2)O与微量元素Sr、V、Ni、Co、Ga、Cu、Ba、Cr和Zn均呈现一致的变化趋势;在MIS2末次冰盛期和MIS1早期中的BФlling-AllerФd暖期和新仙女木冷期,K/Na、Al/Na、化学蚀变指数、化学风化指数和古温度等指标与东亚季风区气候呈现一致的变化,同时与全球尺度的事件具有同步性,因此认为晚更新世晚期华北平原的气候变化可归因于全球气候系统下东亚季风区的演化。

广西大厂多金属矿区河流中Sb和As的迁移及环境影响

以广西大厂多金属矿山为例，对其矿山尾矿堆及地表河流进行采样，研究矿山开采中释放的毒害元素Sb和As对河流水环境的影响．结果表明，矿渣堆中的w（Sb）和w（As）分别为175～7119和309～24233mg／kg；选厂排水中ρ（Sb）和ρ（As）最高值分别为5475和179μg/L；受矿山影响的河流中的ρ（Sb）和ρ（As）平均值在枯水期为630和100μg/L，在丰水期为497和65μg／L．该矿山的开采致使选厂排水和矿山尾渣均对矿区河流中重金属含量做出显著贡献，已对周边河流产生严重影响，造成了刁江上游河水的污染．sb与As虽然化学性质相似，但二者在河水中的迁移特性仍有明显的差别，As在河水中的衰减强于Sb．河水中Sb和As的影响范围都很大，模拟计算表明，Sb和As的影响范围分别离矿山区约120和60km．

广西南丹大厂超大型锡多金属矿床的成矿时代

通过对广西南丹大厂用多金属矿床91号和100号矿体中透长石和石英的常规快中子活化和激光原位^(40)Ar/^(39)Ar法同位素年代学的研究,获得91号矿体块状锡石硫化物矿石中石英的^(40)Ar/^(39)Ar坪年龄为94.52±0.33 Ma,等时线年龄为 95.37±0.45 Ma,反等时线年龄为 94.89±0.16 Ma,透长石的激光^(40)Ar/^(39)Ar等时线年龄为91.4±2.9 Ma;100号矿体石英的坪年龄为 94.56±0.45 Ma,等时线年龄为 93.5±1.2 Ma,反等时线年龄为 93.29±0.16 Ma。这些资料有助于表明大厂锡矿形成于燕山期,在成因上证实后生成因的看法,并且表明产出特征不同的91号矿体与100号矿体是基本同时形成的。结合100号矿体规模巨大但围岩蚀变欠发育的特点,提出了含矿流体进入古溶洞后,由于突然的减压降温而导致成矿物质超常聚集的“失压沸腾”成矿机制。