The Pemali tin deposit,Bangka, Indonesia     

M. O. Schwartz  Surjono 《Mineralium Deposita》1991,26(1):18-25

The Pemali tin deposit is located in a Triassic granite pluton the magmatic evolution of which is characterized by a decrease of compatible Ca, Mg, Ti, P and Zr in the sequence: medium- to coarse-grained biotite granite, megacrystic medium-grained biotite granite, two-mica granite/muscovite granite. The tin mineralization is confined to the two-mica granite and consists of disseminated cassiterite as well as greisen-bordered veins. The highly evolved muscovite granite is tin-barren and is distinguished from the two-mica granite by its low mica content and low loss-on-ignition values. The fluid inclusions in quartz and fluorite of the two-mica granite and of the greisen homogenize in the 115–410 °C temperature range; the salinities are in the range of 0.4–23 equiv wt% NaCl and the CO₂ concentrations are < 2 mole%.  相似文献   

新疆阿尔泰巴斯铁列克钨多金属矿区花岗岩黑云母特征及成岩成矿意义     

柴凤梅  李永  王雯  包长甲  祁冬梅  张雪冰  田猛 《矿床地质》2023,42(1):1-21

黑云母是花岗质岩石中常见的造岩矿物,其成分可以有效指示花岗岩形成的物理化学条件和岩石成因。巴斯铁列克矿床是近年来在新疆阿尔泰造山带南缘发现的首例二叠纪矽卡岩型钨多金属矿床。矿区出露多种类型二叠纪含钨花岗岩。为理清花岗质岩体之间、岩体与钨多金属矿化之间的关系,文章采用电子探针测定了黑云母花岗岩、二长花岗岩、二云母花岗岩和钾长花岗岩中的黑云母成分。结果表明,所有黑云母具有富铁、高铝、贫镁特征,含铁指数(Fe²⁺/(Mg+Fe²⁺))为0.66~0.80,二云母花岗岩属铁质黑云母而黑云母花岗岩、二长花岗岩和钾长花岗岩属铁叶黑云母。所有岩石是具有A型特征的I型花岗岩。不同类型岩石中黑云母的成分差异与岩浆来源、分异演化程度有关。二云母花岗岩中黑云母的w(MgO)与结晶温度最高,与黑云母平衡流体的log(fHF/fHCl)值（-1.13~-1.25）最低,log(fH₂O/fHF)值（4.64~4.96）最高,母岩浆相对富Cl;黑云母花岗岩中log(fHF/fHCl)值最高,log(fH₂O/fHF)最低,与二长花岗岩是同一岩浆房不同演化阶段的产物,与二云母花岗岩和钾长花岗岩属不同的岩浆体系,母岩浆相对富F元素。黑云母花岗岩与W矿化关系更密切。  相似文献   

Structure, age and mode of emplacement of the Hercynian Bordères-Louron pluton (Central Pyrenees, France)     

Gérard Gleizes  Gérard Crevon  Asfawossen Asrat  Pierre Barbey 《International Journal of Earth Sciences》2006,95(6):1039-1052

The Hercynian Bordères-Louron pluton (20 km²) in the Central Pyrenees intrudes Devonian and Carboniferous metasediments. It shows a concentric zoning and consists of a significant proportion of (quartz) gabbros in its periphery, and of granodiorites, biotite monzogranites and biotite-muscovite monzogranites in its core. AMS study shows that the pluton corresponds to an elongated dome with a N100°E-trending axis. The anisotropy intensity Ppara% is high in the south and in the core of the pluton, whereas it is low in the north. The shape parameter T indicates that the fabric is strongly planar in a large central band oriented NW-SE, whereas it is strongly linear in the western and eastern tips of the pluton. These characteristics suggest that the Bordères-Louron pluton emplaced in two episodes: (1) intrusion of mafic magmas along a N100°E sill parallel to the regional foliation of the host metasediments; and (2) injection of three successive silicic batches (granodiorite, biotite monzogranite, two-micas monzogranite) which pushed aside the early mafic injections. In situ U-Pb dating of zircon grains indicates that the emplacement age of the biotite monzogranite is 309 ± 4 Ma, synchronous with the D ₂ dextral transpressive event and close to the ages of the eastern Pyrenean plutons, may be slightly older.  相似文献   

Zircon Hf signatures from granitic orthogneisses of the Spanish Central System: Significance and sources of the Cambro-Ordovician magmatism in the Iberian Variscan Belt     

《Gondwana Research》2016

Metagranitic orthogneisses are abundant in the Central Iberian Zone (CIZ). This felsic magmatism has a highly peraluminous composition (A/CNK = 1.07–1.62) defining a typical S-type granite character, common in crustal thickening environments. The studied Spanish Central System (SCS) orthogneisses yield Late Cambrian to Early Ordovician U–Pb zircon ages (496 to 481 Ma), overlapping with the available literature data (mostly from 477 to 500 Ma). These orthogneisses are intrusive into metasedimentary sequences from the northern CIZ that have been recently dated at about 536 Ma. Late Ediacaran inherited zircons are common in the SCS orthogneisses (10% to 75% of the total zircon population). Most inheritance ranges from Neoproterozoic to Late Mesoproterozoic in age (0.52 to 1.25 Ga) and shows marked positive ԐHf_t values (>+5). This long period of Proterozoic juvenile input is only recognized in the metasedimentary rocks of the Schist–Greywacke Complex, outcropping in the southern CIZ. The proposed linkage between the southern CIZ metasediments (as sources) and the studied orthogneisses is reinforced by their similar Nd isotopic signatures (from − 2.81 to − 4.95) and the highly peraluminous character of the orthogneisses. The intrusion of this felsic magmatism within the northern CIZ, having been generated by melting of the more distal southern CIZ metasediments, together with their recycled crustal origin, suggests crustal thickening of the northern Gondwana margin during a period of flat subduction. The orthogneisses define a large linear S-type magmatic belt cropping out for over 650 km from central Spain to Galicia. The ~ 35 Ma delay between sedimentation and granite intrusion is a typical time interval for crustal thickening models. This thickening stage evolved toward a passive margin setting, allowing the deposition of the siliciclastic Ordovician series which covered the previous terranes. Minor Floian-aged tholeiitic magmatism, giving rise to scarce metabasite outcrops in the SCS, probably postdates thickening and marks this tectonic change in central Iberia.  相似文献   

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar     

Ewa Słaby  Andrzej Domonik  Michał Śmigielski  Katarzyna Majzner  Gediminas Motuza  Jens Götze  Klaus Simon  Izabela Moszumańska  Łukasz Kruszewski  Paweł Rydelek 《Contributions to Mineralogy and Petrology》2014,167(4):1-23

Tourmalinization associated with peraluminous granitic intrusions in metapelitic host-rocks has been widely recorded in the Iberian Peninsula, given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of Sn-W mineralizations. In the Penamacor-Monsanto granite pluton (Central Eastern Portugal, Central Iberian Zone), tourmaline occurs: (1) as accessory phase in two-mica granitic rocks, muscovite-granites and aplites, (2) in quartz (±mica)-tourmaline rocks (tourmalinites) in several exocontact locations, and (3) as a rare detrital phase in contact zone hornfels and metapelitic host-rocks. Electron microprobe and stable isotope (δ¹⁸O, δD, δ¹¹B) data provide clear distinctions between tourmaline populations from these different settings: (a) schorl–oxyschorl tourmalines from granitic rocks have variable foititic component (^X□ = 17–57 %) and Mg/(Mg + Fe) ratios (0.19–0.50 in two-mica granitic rocks, and 0.05–0.19 in the more differentiated muscovite-granite and aplites); granitic tourmalines have constant δ¹⁸O values (12.1 ± 0.1 ‰), with wider-ranging δD (?78.2 ± 4.7 ‰) and δ¹¹B (?10.7 to ?9.0 ‰) values; (b) vein/breccia oxyschorl [Mg/(Mg + Fe) = 0.31–0.44] results from late, B- and Fe-enriched magma-derived fluids and is characterized by δ¹⁸O = 12.4 ‰, δD = ?29.5 ‰, and δ¹¹B = ?9.3 ‰, while replacement tourmalines have more dravitic compositions [Mg/(Mg + Fe) = 0.26–0.64], close to that of detrital tourmaline in the surrounding metapelitic rocks, and yield relatively constant δ¹⁸O values (13.1–13.3 ‰), though wider-ranging δD (?58.5 to ?36.5 ‰) and δ¹¹B (?10.2 to ?8.8 ‰) values; and (c) detrital tourmaline in contact rocks and regional host metasediments is mainly dravite [Mg/(Mg + Fe) = 0.35–0.78] and oxydravite [Mg/(Mg + Fe) = 0.51–0.58], respectively. Boron contents of the granitic rocks are low (<650 ppm) compared to the minimum B contents normally required for tourmaline saturation in granitic melts, implying loss of B and other volatiles to the surrounding host-rocks during the late-magmatic stages. This process was responsible for tourmalinization at the exocontact of the Penamacor-Monsanto pluton, either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin (vein/breccia tourmalinites), or as replacement of mafic minerals (chlorite or biotite) in the host-rocks (replacement tourmalinites) along the exocontact of the granite. Thermometry based on ¹⁸O equilibrium fractionation between tourmaline and fluid indicates that a late, B-enriched magmatic aqueous fluid (av. δ¹⁸O ~12.1 ‰, at ~600 °C) precipitated the vein/breccia tourmaline (δ¹⁸O ~12.4 ‰) at ~500–550 °C, and later interacted with the cooler surrounding host-rocks to produce tourmaline at lower temperatures (400–450 °C), and an average δ¹⁸O ~13.2 ‰, closer to the values for the host-rock. Although B-metasomatism associated with some granitic plutons in the Iberian Peninsula seems to be relatively confined in space, extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of Variscan magmatism and related mineralizations.  相似文献   

A Precambrian fayalite granite from the south coast of Western Australia     

N.C.N. Stephenson  H.D. Hensel 《Lithos》1978,11(3):209-218

A Precambrian fayalite granite outcropping at Lower King, near Albany, Western Australia, is interpreted as a high-Fe²⁺/(Fe²⁺ + Mg) analogue of charnockite. Calculation of the original titanomagnetite composition from analytical data on ilmenomagnetite ‘exsolution’ intergrowths suggests initial crystallisation of opaque oxides at about 940°C and 10^?12 bars f_o2. This result indicates a magmatic origin for the rock. Other determinable points on the T-f_o2 cooling curve of the fayalite granite pluton include crystallisation of biotite at roughly 800–820°C and 10^?14.5 bars f_o2, and final equilibration of opaque oxides below 550°C and 10^?23 bars f_o2. Mineralogical data on nearby granulite facies country rocks suggest a regional total pressure of roughly 5 kb, and hence the depth of pluton emplacement was probably around 18–19 km. Thus the Lower King fayalite granite is believed to have crystallised from water-deficient, high-T melt or partial melt generated, possibly from metasedimentary rocks, deep in the crust under granulite facies conditions.  相似文献   

滇西“三江”地区临沧花岗岩基中三叠世碱长花岗岩的发现及其意义     

廖世勇  尹福光  王冬兵  唐渊  孙志明  孙洁 《岩石矿物学杂志》2014,33(1):1-12

在野外调研的基础上,对滇西“三江”地区临沧花岗岩基中勐库碱长花岗岩体的年代学、岩石学和地球化学开展了较系统的研究。结果显示,勐库岩体的锆石LA-ICP-MS U-Pb年龄为236.2±3.7 Ma,表明岩体应形成于中三叠世,而非前人认为的新生代。全岩主、微量元素,Sr同位素和锆石微量元素特征显示岩体属于S型花岗岩系列,来自于与临沧花岗岩基相类似的地壳沉积物源区的部分熔融,并经历了高程度的结晶分异作用。以勐库岩体为代表的碱长花岗岩与临沧花岗岩基形成时代一致,表明碱长花岗岩应为临沧花岗岩基的重要组成部分。除已报道的黑云母二长花岗岩类和黑云母花岗闪长岩类外,临沧花岗岩基还应包括较广泛分布的碱长花岗岩类。本文同时揭示,由于临沧花岗岩基中以勐库岩体为代表的碱长花岗岩并非早前认为的新生代岩体,“三江”南段特别是临沧地块前人划分的新生代岩体分布范围和规模可能需要重估。  相似文献   

2.8 Ga Old Anorogenic Granite-Acid Volcanics Association from Western Margin of the Singhbhum-Orissa Craton,Eastern India     

《Gondwana Research》2001,4(3):465-475

The Tamperkola granite-acid volcanics association occurring at the western margin of the Archaean Singhbhum-Orissa Iron Ore Craton (SOC), eastern India, is intrusive into the Darjing Group which represents a sequence of mobile belt metasediments in this part of the SOC. The Darjing Group rests unconformably on the Bonai Granite (∼3.2 Ga old). Absence of any deformational imprints of the country rock metasediments on the Tamperkola granite acid volcanics together with its undeformed and unmetamorphosed nature, its alkali feldspar dominant mineralogy, and its high SiO₂ and Na₂O + K₂O and low MgO and CaO contents suggest that this granite-acid volcanics association is anorogenic in nature. Two representative samples-one each from the granite and the acid volcanics have been dated by in situ ²⁰⁷Pb/²⁰⁶Pb zircon dating method using a small ion-microprobe. Minimum age of crystallisation of the acid volcanics is found to be 2.8 Ga. Strong peak in the ²⁰⁷Pb/²⁰⁶ Pb frequency diagram and equality of the observed and expected errors in radiogenic ²⁰⁷Pb/²⁰⁶Pb ratios suggest that this age probably represents the true age of formation of the volcanics. The age data place the deposition and metamorphism of the mobile belt metasediments of the Darjing Group in between 3.2 and 2.8 Ga. Occurrence of 2.9–2.8 Ga old small granitoid plutons, alkali-feldspar granite to syenogranite in composition, is also known from the southern margin of the SOC. Therefore, it appears that around 2.9–2.8 Ga small alkali granite bodies formed at the marginal part of this cratonic block after its stabilisation at ∼3.1 Ga.  相似文献   

Datation U–Pb des deux faciès du granite de Soultz (Fossé rhénan,France)     

Alain Cocherie  Catherine Guerrot  C.Mark Fanning  Albert Genter 《Comptes Rendus Geoscience》2004,336(9):775-787

Deep boreholes drilled in the basement of the Rhine Graben at Soultz-sous-Forêts have shown the presence of an ubiquitous monzogranite. Borehole GPK-2, with a total depth of 5090 m, also intersected a more leucocratic fine-grained two-mica granite, locally present below 4860 m depth and continuously found between 5047 and 5090 m. Thanks to trace elements and in particular to REE (rare-earth elements), it could be shown that the leucocratic rock is a differentiated expression of the potassic magma that was at the origin of the monzogranite pluton. This model agrees with Sr–Nd isotope data, even though a slight contribution from the pre-existing basement should be considered as well. Use of the U–Pb method on monzogranite from EPS-1 – after zircon dissolution – has yielded an emplacement age of 334.0+3.8/?3.5 Ma $\text{(2}\text{σ)}$. Point dates obtained by SHRIMP II on the rare zircons from the fine-grained granite showed that it was emplaced in a basement with very heterogeneous ages, ranging from Early Proterozoic to Silurian. The estimated crystallization age of the last granite is 327±7 Ma $\text{(2}\text{σ)}$, slightly later than, or sub-contemporaneous with, the emplacement of the common monzogranite, in agreement with structural constrains. To cite this article: A. Cocherie et al., C. R. Geoscience 336 (2004).  相似文献   

Mineralogy of New Caledonian metamorphic rocks     

Philippa M. Black 《Contributions to Mineralogy and Petrology》1975,49(4):269-284

Variations in chemistry and related physical properties of sheet silicates in the Ouégoa district with metamorphic grade are investigated. Weakly metamorphosed rocks prior to the crystallization of lawsonite contain phengite (d ₀₀₆=3.317–3.323 Å), chlorite and occasionally paragonite while interstratified basaltic sills contain chlorite, minor phengite and stilpnomelane. Pyrophyllite crystallizes before lawsonite in some metamorphosed acid tuffs and is also stable in the lawsonite zone. Paragonite, phengite and chlorite appear to be stable through the sequence from weakly metamorphosed rocks into high-grade “eclogitic” schists and gneisses. Optical, chemical and some X-ray diffraction data is given for representative sheet silicates. Electron probe analyses of 55 phengites, 21 paragonites, 57 chlorites, 12 vermiculites, 2 stilpnomelanes, and 2 chloritoids are presented in graphical form. All K-micas analysed are consistently phengitic (3.29–3.55 Si^iv ions per formula unit) and show limited solid solution with paragonite (4 to 13% Pa). The K∶Na ratio of the phengite is strongly dependant on the assemblage in which it occurs; the amount of phengite component and its Fe∶Mg ratio depends on bulk-rock composition. Phengites from acid volcanics have the highest Fe∶Mg ratio, highest phengite component and β refractive indices. Phengites from basic volcanics and metasediments of the epidote zone have the lowest Fe∶Mg ratio. Phengites from lawsonite-zone metasediments have intermediate Fe∶Mg ratios. The phengites show a small decrease in phengite component with increasing metamorphic grade. d ₀₀₆ for phengites varied from 3.302 to 3.323 Å but at least in the lawsonite and epidote zones appears to reflect composition and had little systematic variation with metamorphic grade; phengites from very low-grade rocks showed the longest values of d ₀₀₆. Paragonite shows almost no phengite-type substitution and only limited solid solution (4–12%) with muscovite. All paragonites (6) and most phengites (20) which have been examined are 2M₁ polymorphs; one Fe²⁺-phengite appears to be a 1M polymorph. The chemistry of chlorites closely reflects parent-rock chemistry. Chlorites from metasediments have distinctly higher Fe/(Fe+Mg) ratios than chlorites from basic igneous rocks; chlorites from the lawsonite and lawsonite-epidote transitional zone metasediments have the highest Fe/(Fe+Mg) ratios. In metabasalts Fe/(Fe+Mg) ratios appear to reflect individual variations in bulk-rock chemistry and show no direct correlation with metamorphic grade. There is little difference in Al/(Si+Al) ratio between chlorites from sediments and basic igneous rocks although in both lithologies the chlorites from the epidote zone appear to be slightly more aluminous. Fe-rich chlorites of the lawsonite zone metasediments have been altered by a process involving leaching of Fe and Mg and introduction of alkalies to a brown pleochroic Fe-vermiculite. Chemical and physical data for this vermiculite are given. The decrease in Fe/(Fe+Mg) ratio in chlorites and phengites on passing from the lawsonite to the epidote zone can be correlated with the crystallization of Fe-rich epidote and almandine in the epidote zone. Elemental partitioning between coexisting minerals has shown Ti to be partitioned into phengite, while Fe and Mn are strongly partitioned into chlorite. When either stilpnomelane or chloritoid coexists with phengite or chlorite, Fe and Mn are slightly enriched in the stilpnomelane or chloritoid relative to the chlorite.  相似文献