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1.
Summary Vivianite from Catavi Mine, Llallagua, Bolivia, has a near ideal composition with traces of Mg, Zn and Mn. Total rare-earth elements are < 1,gmg/g. Mössbauer spectroscopy shows FeIII/(FeII + FeIII) is approximately 0.04.a = 10.030Å,b = 13.434Å,c = 4.714Å, = 102.73dg. The middle-infrared powder spectrum shows H2O-related bands at 3490, 3290, 3130 cm–1 (stretch), 1618 cm–1 (bend), 825 cm–1 (rock), and at 665 cm–1 a possible M-OH2 twist. P04 bands occur at 1045-940 cm–1 (stretch) and 570-450 cm–1 (bend). Corresponding laser Raman microprobe bands occur at 1051 (ms), 986 (m), 948 (vs), 867 (mw), 828 (w), 568, 532, 453 (m), 442 (mw). Weak Raman bands at about 342, 303, 270 (w), 235 (ms), 227 (sh, ms), 196 (ms), 187 (sh, m), 162 (mw), and 126 (m) may arise from lattice vibrations. Differential thermal responses include a major endotherm from 115–235°C with a shoulder at 170°C and a maximum at 210°C resulting from loss of structural water combined with oxidation of Fe2+, and two small exotherms with maxima at 605 and 780°C related to structural transformations.
Charakterisierung des Vivianits von Catavi, Llallagua, Bolivien
Zusammenfassung Vivianit von der Catavi Mine, Llallagua, Bolivien zeigt annähernd ideale Zusammensetzung mit Spuren von Mg, Zn und Mn. Der gesamte Gehalt an seltenen EvolElementen ist < 1 ppm. Die Mössbauer Spektroskopie liefert ein Fe3+/(Fe2+ + Fe3+) Verhältnis von ungefähr 0.04.a = 10.030,b = 13.434,c = 4.714 Å, = 102.73°. Das Infrarot-Pulverspektrum zeigt dem H20 zuzuordnende Banden bei 3490, 3290, 3130 cm–1 (Streckschwingungen), 1618 cm–1 (Deformationsschwingung), 825 cm–1 (Schaukelschwingung) und eine mögliche M-OH2 Torsionsschwingung bei 665 cm–1. PO4 Banden liegen bei 1045-940 cm–1 (Streckschwingung) und 570-450 cm–1 (Deformations-schwingung). Entsprechende Banden der Laser Raman Mikrosonde liegen bei 1051 (mst), 986 (m), 948 (sst) 867 (mschw), 828 (schw), 568, 532, 453 (m), 442 (mschw). Raman Banden bei etwa 342, 303, 270 (schw), 235 (mst), 227 (Schulter, mst), 196 (mst), 187 (Schulter, m), 162 (mschw) und 126 (m) können auf Gitterschwingungen zurückgeführt werden. Differential-thermoanalytische Untersuchungen zeigen einen endothermen Bereich von 115–235°C mit einer Schulter bei 170 und einem Maximum bei 210°C, was auf den Verlust von strukturellem Wasser, das an eine Oxidation des Fe2+ gebunden ist, zurückzuführen ist; zwei auf strukturelle Transformationen zurückzuführende exotherme Maxima liegen bei 605 und 780°C.


With 4 Figures  相似文献   

2.
对安徽铜陵新桥铜-硫-铁-金矿床区内的石英闪长岩和辉绿岩中的锆石分别进行了SHRIMP精确定年研究,石英闪长岩中锆石206Pb/238U年龄为(140.4±2.2)Ma,辉绿岩中锆石的年龄较复杂,其中发现了元古代锆石颗粒,其锆石207Pb/206Pb年龄为(2261±14)Ma,(1612±8)Ma,(919±12)Ma,(831±17)Ma。另外还有一组早古生代年龄的锆石,锆石206Pb/238U年龄为(443±13)Ma。以上这些新资料说明该区可能存在元古代基底的信息,且燕山期岩浆活动对本区成矿具有重要意义。  相似文献   

3.
Monazite in granulite facies metatexite migmatites (Christie Gneiss) hosting the Challenger Au deposit, South Australia, records a series of growth and resorption stages over a c. 60 Myr period between 2470 and 2410 Ma. A combination of electron microprobe X‐ray mapping and in situ ion‐microprobe dating was used to delineate and date five compositional domains. The oldest prograde metamorphic components are preserved in granoblastic gneisses surrounding the deposit, and as small high‐Y cores in large monazite grains in Au‐bearing migmatites. In metatexite leucosomes, these cores were partially resorbed prior to the growth of large high‐Th monazite domains that crystallized during partial melting and stromatic migmatite development at c. 2443 Ma. Subsequent heating to biotite dehydration conditions (c. 850 °C at 7 kbar) caused further partial melting roughly 10–15 Myr later, giving rise to c. 2428 Ma domains surrounding partly resorbed 2443 Ma grains that were entrained in the higher‐temperature melts. This period of partial melting coincided with isoclinal folding culminating in dextral transpression and represents the most likely window for remobilization of Au‐bearing polymetallic sulphide melts into low‐strain domains. Localized reaction of residual melt with the granulite facies assemblage during cooling gave rise to narrow high‐Y rims dated at 2414 ± 7 Ma. Although monazite from unmineralized granoblastic gneisses and migmatitic ore zones display the same range of U‐Pb dates, monazite in migmatites displays a higher overall Ca + Th + U content, indicating that compositional heterogeneities between ore zones and host rocks developed prior to 2470 Ma, perhaps a consequence of the hydrothermal alteration inferred to have accompanied gold mineralization.  相似文献   

4.
冷水坑斑岩型银铅锌矿床是中国目前唯一的典型斑岩型银铅锌矿床,对于该矿床的成矿斑岩的形成时代至今仍没有精确的年龄数据。本文通过对冷水坑斑岩型银铅锌矿床成矿斑岩(花岗斑岩)样品中的锆石11个测试点的SHRIMP锆石U-Pb年代学研究,得出206Pb/238U加权平均年龄为(162.0±2)Ma(MSWD=1.4),因此,认为冷水坑花岗斑岩的形成年代为(162.0±2)Ma。冷水坑含矿斑岩成岩年龄与成矿年龄高度一致,成岩年龄与成矿作用开始时间差异不明显。此外,由冷水坑矿床成岩和成矿年龄数据推断出矿化持续时间约27Ma。  相似文献   

5.
界牌岭锡多金属矿床是湘南地区一个与花岗斑岩关系十分密切的大型矿床。本文通过对含矿花岗斑岩样品中的锆石进行SHPIMP U-Pb年代学研究,获得206Pb/238U加权平均年龄为92.0±1.6 Ma(MSWD=1.05),显示为晚白垩世侵位。含矿花岗斑岩成岩年龄与矿床锡矿成矿年龄基本一致,它们应属于同一构造-岩浆活动的产物。  相似文献   

6.
Ion microprobe dating of zircon and monazite from high-grade gneisses has been used to (1) determine the timing of metamorphism in the Western Province of New Zealand, and (2) constrain the age of the protoliths from which the metamorphic rocks were derived. The Western Province comprises Westland, where mainly upper crustal rocks are exposed, and Fiordland, where middle to lower crustal levels crop out. In Westland, the oldest recognisable metamorphic event occurred at 360–370 Ma, penecontemporaneously with intrusion of the mid-Palaeozoic Karamea Batholith (c. 375 Ma). Metamorphism took place under low-pressure/high-temperature conditions, resulting in upper-amphibolite sillimanite-grade metamorphism of Lower Palaeozoic pelites (Greenland Group). Orthogneisses of younger (Cretaceous) age formed during emplacement of the Rahu Suite granite intrusives (c. 110 Ma) and were derived from protoliths including Cretaceous Separation Point suite and Devonian Karamea suite granites. In Fiordland, high-grade paragneisses with Greenland Group zircon age patterns were metamorphosed (M1) to sillimanite grade at 360 Ma. Concomitant with crustal thickening and further granite emplacement, M1 mineral assemblages were overprinted by higher-pressure kyanite-grade metamorphism (M2) at 330 Ma. It remains unclear whether the M2 event in Fiordland was primarily due to tectonic burial, as suggested by regional recumbent isoclinal folding, or whether it was due to magmatic loading, in keeping with the significant volumes of granite magma intruded at higher structural levels in the formerly contiguous Westland region. Metamorphism in Fiordland accompanied and outlasted emplacement of the Western Fiordland Orthogneiss (WFO) at 110–125 Ma. The WFO equilibrated under granulite facies conditions, whereas cover rocks underwent more limited recrystallization except for high-strain shear zones where conditions of lower to middle amphibolite facies were met. The juxtaposition of Palaeozoic kyanite-grade rocks against Cretaceous WFO granulites resulted from late Mesozoic extensional deformation and development of metamorphic core complexes in the Western Province.  相似文献   

7.
诸广山复式花岗岩基位于湘、赣、粤三省交界处,是南岭花岗岩的重要组成部分,由南体和北体组成,出露面积大于5000 km2,形成于加里东期、印支期、燕山期3个时代。通过对诸广山北体3期花岗岩锆石SHRIMP U-Pb定年,结果表明,加里东期花岗闪长岩锆石SHRIMP U-Pb年龄为(414.5±4.5)Ma(n=13,MSWD=0.52)、(417.3±4.8)Ma(n=12,MSWD=0.84),形成于晚志留世末。印支期黑云母二长花岗岩锆石SHRIMP U-Pb年龄(207.5±2.7)Ma(n=10,MSWD=1.6),形成于晚三叠世末。燕山期二云母二长花岗岩锆石SHRIMP U-Pb年龄(148.2±1.7)Ma(n=13,MSWD=0.93),形成于晚侏罗世。该成果为南岭地区构造-岩浆演化及成矿作用研究,提供了重要的花岗岩年代学依据。  相似文献   

8.
阿拉套山南缘岩浆岩锆石SHRIMP年代学研究   总被引:1,自引:1,他引:1  
位于中国与哈萨克什坦国边境的阿拉套山南缘,火山岩及花岗岩十分发育。其中流纹岩分布广泛,仅研究区内面积达370.8km~2,与下伏早石炭世阿克沙克组及晚石炭世东图津河组呈角度不整合或假整合,SHRIMP 锆石 U-Pb 年龄300±5Ma。乌拉斯台花岗岩体是研究区内规模最大的岩体,出露面积约82km~2,侵入于早石炭统阿克沙克组及至晚石炭统东图津河组以及早二叠统乌郎组火山岩内,与围岩界线清楚。岩体形态不规则,由4个侵入次岩体组成。第4次侵入的花岗闪长岩体 HRIMP 锆石 U-Pb 年龄为294±4Ma。夏尔敖腊岩体为由4个侵入次组成的岩体,侵入于早石炭统内,平面上呈不规则椭圆形,出露面积近10km~2,主要岩性为二长花岗岩。出露规模较大的第6次侵入岩体的 SHRIMP 锆石 U-Pb 年龄为299±6Ma。研究表明,新疆阿拉套山南缘岩浆岩,SHRIMP 锆石 U-Pb 同位素年龄300Ma 左右,主要形成于晚石炭世末至早二叠世初,为同一构造-岩浆作用下的产物。  相似文献   

9.
桂东南云开地区变质杂岩锆石SHRIMP U-Pb年代学   总被引:23,自引:1,他引:23  
对位于华夏古陆东南部的广西云开地区大面积出露的晚前寒武纪变质杂岩中的主体花岗质片麻岩、中深变质的天堂山岩群石榴辉石岩和中浅变质的云开岩群洋中脊型变质基性火山岩(斜长角闪岩)进行了高精度锆石SHRIMP U-Pb定年.获得天堂山岩群石榴辉石岩的形成年龄为1894Ma±17Ma和1847Ma±59Ma,表明其时代为古元古代;云开岩群洋中脊型变质基性火山岩(斜长角闪岩)的喷发年龄为1462Ma±28Ma,证明该地区存在中(-新)元古代的古洋壳残片;获得花岗质片麻岩的侵入年龄为906Ma±24Ma,应为1000Ma前后发生的全球性Grenville期(四堡期)造山作用的产物,并获得2702Ma±13Ma的继承碎屑锆石年龄,这是云开地区乃至华夏古陆目前获得的最古老年龄,证明华夏古陆曾存在新太古代陆壳物质.  相似文献   

10.
大坪金矿是哀牢山-红河韧性剪切带南段最重要的大型金矿床之一,由于其成矿时代和构造背景一直存在争议,不利于带内金矿床成矿模型的建立和进一步找矿勘探.本文利用LA-ICP-MS对矿区内含金石英脉中热液错石、闪长岩和花岗闪长岩脉中岩浆锆石开展了U-Pb年代学研究,获得热液锆石U-Pb年龄为760±10 Ma,表明大坪金矿区可...  相似文献   

11.
12.
Sr-Nd-Pb-Hf isotope mapping combined with U-Pb zircon SHRIMP ages of granitoids from four sampling profiles across terrane boundaries in Uzbekistan reveal distinct reservoir types (cratonic and accretionary), witnessed by the diverse nature and origin of the predominant Paleozoic granitic magmatism that provided hosts for major ore-bodies. The study region comprises four major terranes, including 1) the Sultan-Uvais terrane, 2) the Kyzylkum-Nurata Segment and 3) the Gissar Segment of the South Tien Shan and 4) the Chatkal-Kurama terrane of the Middle Tien Shan. Sr-Nd isotope analyses show a wide range of εNdt (− 5 to + 7) and (87Sr/86Sr)t of 0.704–0.707, indicating involvement of both mantle-derived material and older crustal sources. A wide range of Hf-isotope compositions found in zircons of Chatkal-Kurama granites, Middle Tien Shan (εHf mainly ~  5 to + 5), could be due to recycling of older crustal protolith(s); in particular, the earliest (Silurian) granites may be directly derived from 1.5 to 1.7 Ga lower crust. In the Southern Tien Shan, some involvement of subducted oceanic crust is evidenced by strongly juvenile εHft values of up to + 14 and + 16 (Sultan-Uvais, Teskuduk-Kyzylkum). Permo-Carboniferous granitoids, which occur across all terranes also exhibit a wide range of isotope signatures, corresponding to Mesoproterozoic–Neoproterozoic crustal protoliths with a westward increase in juvenile contributions. Pb isotopes (whole-rock) imply the dominance of a crustal component and crust-mantle mixing processes. New age data confirmed: 1) old age of the Turkestan Ocean (505 Ma in Sultan-Uvais), 2) fragments of Silurian island arcs in the accretionary complex of the Chatkal-Kurama terrane (granites of 429–416 Ma) and in the upper allochthon of the South Tien Shan (gabbro 438 Ma in Tamdytau), and 3) a significant volume of granitoid magmatism of subduction or early-collisional stages (around 320–310 Ma) in the Chatkal-Kurama Segment and especially in the Gissar Segment. The westernmost part of the Tien Shan is characterized by multiple subduction processes responsible for 300 million years of geodynamic evolution history (accretionary collage, crustal growth) with the pre-Mesozoic crust formation concluded by Permian post-collisional extensional magmatism.  相似文献   

13.
14.
金厂沟梁-二道沟金矿田内花岗岩类侵入体SHRIMP锆石U-Ph定年结果表明,该区中生代以来到少经历了三次中酸性岩浆侵入作用,它们分别以西台子二长花岗岩、娄上含辉石石英闪长岩和西对面沟花岗闪长岩及闪长玢岩脉在218±4Ma(印支期)、161±1Ma(燕山早期)和126±1Ma(燕山晚期)的侵位为标志。花岗岩类的地球化学资料表明,这些花岗岩类侵入体形成与造山作用有关,为造山后或陆内拉张作用的产物。二道沟矿区成矿前或成矿期闪长玢岩脉的年龄126±1Ma限定了该区金矿化的最大年龄;结合前人有关年代学资料,认为本区金矿化应发生在126~118Ma。这说明金厂沟梁-二道沟金矿田的金矿床与我国胶东、小秦岭和辽东等地区的金矿床是同时形成的,再次证明燕山晚期是中国最重要而广泛的金成矿期。此外,在这些主要的金矿区内,金矿化时间上均具有与各自区内最晚一次花岗质岩浆作用同时或稍晚的特征,这可能指示金矿床是造山作用或区域构造-岩浆演化最晚期的产物。  相似文献   

15.
Two Rongcheng eclogite‐bearing peridotite bodies (Chijiadian and Macaokuang) occur as lenses within the country rock gneiss of the northern Sulu terrane. The Chijiadian ultramafic body consists of garnet lherzolite, whereas the Macaokuang body is mainly meta‐dunite. Both ultramafics are characterized by high MgO contents, low fertile element concentrations and total REE contents, which suggests that they were derived from depleted, residual mantle. High FeO contents, an LREE‐enriched pattern and trace‐element contents indicate that the bulk‐rock compositions of these ultramafic rocks were modified by metasomatism. Oxygen‐isotope compositions of analysed garnet, olivine, clinopyroxene and orthopyroxene from these two ultramafic bodies are between +5.2‰ and +6.2‰ (δ18O), in the range of typical mantle values (+5.1 to +6.6‰). The eclogite enclosed within the Chijiadian lherzolite shows an LREE‐enriched pattern and was formed by melts derived from variable degrees (0.005–0.05) of partial melting of peridotite. It has higher δ18O values (+7.6‰ for garnet and +7.7‰ for omphacite) than those of lherzolite. Small O‐isotope fractionations (ΔCpx‐Ol: 0.4‰, ΔCpx‐Grt: 0.1‰, ΔGrt‐Ol: 0.3–0.4‰) in both eclogite and ultramafic rocks suggest isotopic equilibrium at high temperature. The P–T estimates suggest that these rocks experienced subduction‐zone ultrahigh‐pressure (UHP) metamorphism at ~700–800 °C, 5 GPa, with a low geothermal gradient. Zircon from the Macaokuang eclogite contains inclusions of garnet and diopside. The 225 ± 2 Ma U/Pb age obtained from these zircon may date either the prograde conditions just before peak metamorphism or the UHP metamorphic event, and therefore constrains the timing of subduction‐related UHP metamorphism for the Rongcheng mafic–ultramafic bodies.  相似文献   

16.
热水岩体位于贵东岩体中部南侧,SHRIMP锆石U-Pb定年结果为162.8±5.8 Ma(MSWD=4.2),属于燕山早期岩浆活动产物.该岩体具有富硅(SiO2平均为76.32%)、富铝(A/CNK值平均为1.14)、钾大于钠(K2 O/Na2O值平均为1.32)和高的P2O5含量(平均为0.41%);大离子元素富集,...  相似文献   

17.
弄如日金矿床位于青藏高原南部冈底斯-喜马拉雅构造区的冈底斯构造-岩浆带东段的中部,是该成矿带内首次发现并评价的浅成低温热液型金锑矿床.文章对该矿区出露的钾长花岗岩和二长花岗斑岩进行了锆石SHRIMP U-Pb测年,并对岩石的主量元素、微量元素进行了分析.测试结果显示,钾长花岗岩的加权平均年龄为(66.6±0.7) Ma,属晚白垩世;岩石富硅[ω(SiO2)平均为76.74%]、富碱(ALK 平均为8.21%),A/CNK均大于1.0,属过铝质高钾钙碱性岩石;稀土元素球粒陨石配分模式图表现为右倾型,LREE富集、HREE亏损,ΣREE平均为66.31×10-6,并且具有明显的Eu负异常(δEu平均为0.40);微量元素原始地幔蛛网图表现出LILE富集、HFSE相对亏损的特征,暗示其可能为弧岩浆作用的产物.二长花岗斑岩的加权平均年龄为(18.8±0.3) Ma,属中新世;岩石富硅[ω(SO2)平均为72 69%]、富碱(ALK平均为6.73%),A/CNK大于1.0,属过铝质高钾钙碱性岩石;稀土元素球粒陨石配分模式图表现为右倾型,LREE富集、HREE亏损,ΣREE平均为77.33×10-6,Eu异常不明显(δEu平均为1.03);在微量元素原始地幔蛛网图上,具有LILE富集、HFSE相对亏损的特征;同时,该岩石还具有较高的La/Yb比值[(La/Yb)N平均为18.53],显示出一定的埃达克岩亲和性.结合区域地质背景表明:弄如日金矿床形成于陆陆碰撞后伸展环境,与区域上近SN向正断层系统及裂谷裂陷带有关的冈底斯含矿斑岩的侵位时代相一致,是区域内中新世岩浆活动所形成的斑岩系统外围的浅成低温热液系统的产物.  相似文献   

18.
对西藏冈底斯带南部雄村铜金矿床的容矿火山岩和外围岩石进行了岩石学、地球化学、锆石年代学研究.雄村容矿火山岩锆石(XC01-1,流纹质凝灰岩)U-Pb SHRIMP年龄的测定值为180.4±3.5 Ma,表明这套火山岩是形成于早侏罗世而不是此前一致公认的晚白垩世.外围二长花岗岩(XTM04-1) U-Pb SHRIMP年龄的测定值为46.6±0.6 Ma,表明其侵位于成矿时代的始新世.结合前人的研究成果,认为雄村铜金矿床与胶东焦家式金矿床具有很大的相似性,属于破碎带蚀变岩型铜金矿床.  相似文献   

19.
The potential genetic link between granites and their host sediments can be assessed using zircon age inheritance patterns. In the Lachlan fold belt, southeastern Australia, granites and associated high-grade metasedimentary rocks intrude low-grade Ordovician country rock. This relationship is well-exposed in the Tallangatta region, northeast Victoria (part of the Wagga-Omeo Metamorphic Complex). In this region granites (two I-types and two S-types) have intruded during the mid-late Silurian between approximately 410–430 Ma based on the ages of magmatic zircons. The age spectra for inherited zircons from the granites have been compared with those of detrital zircons from the enclosing low- and high-grade metasediments. In broad terms, both for detrital zircons in all four sediments and for inherited zircons in three of the four granites, the dominant ages are early Paleozoic and Late Precambrian, with sporadic older Precambrian ages extending up to 3.5 Ga. The ages of the youngest detrital zircons from the low-grade Lockhart and Talgarno terranes limit the time of sedimentation to ca. 466 Ma or younger. The youngest detrital zircons from two samples of the high-grade Gundowring terrane are 473 Ma, making these sediments Ordovician or younger, not Cambrian as originally suggested. However, the individual age spectra for the four selected metasediments are not well matched when closely examined. The age spectra of the inherited zircons in the granites also do not adequately match those in any of the metasediments. Thus, the metasediments might not be representative of the actual source rocks of the granites. While the exact source of the granites cannot be identified from the analysed samples, the existence of a large population of ca. 495 Ma inherited zircon grains in the S-type granites requires that the granite source contains a significant proportion of Cambrian or younger material. This does not preclude the existence of a Precambrian basement to the Lachlan fold belt but indicates that at the level of S-type magma generation, a Cambrian and/or younger protolith is required. Received: 28 August 1998 / Accepted: 7 July 1999  相似文献   

20.
本文对东准噶尔北缘索尔库都克铜钼矿区出露的含矿粗面英安斑岩、粗面斑岩及赋矿围岩安山玢岩进行了详细的SHRIMP锆石U-Pb年代学研究,结果表明:安山玢岩的成岩年龄为411±4Ma,为早泥盆世,表明该矿的赋矿地层应为下泥盆统托让格库都克组;含矿粗面英安斑岩和粗面斑岩成岩年龄分别为387.6±1.8Ma和383.8±1.7Ma,限定索尔库都克铜钼矿床的成矿时代可能为中泥盆世末,并可能经历了晚石炭世的叠加成矿过程。索尔库都克铜钼矿床含矿斑岩的成岩时代与东准噶尔北缘地区斑岩-矽卡岩型矿床含矿斑岩的主体成岩时限(390~375Ma)一致,表明东准噶尔北缘地区构成一条斑岩-矽卡岩Cu-Mo成矿带。  相似文献   

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