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1.
Paul Duuring Stephen M. Rowins Bradley S. M. McKinley Jenni M. Dickinson Larry J. Diakow Young-Seog Kim Robert A. Creaser 《Mineralium Deposita》2009,44(4):435-462
Kemess South is the only Cu–Au–Mo mine in the Toodoggone district and a major Cu and Au producer in British Columbia. Porphyry-style
Cu–Au–Mo mineralization is mainly hosted by the tabular, SW-plunging, 199.6 ± 0.6-Ma Maple Leaf granodiorite, which intrudes
tightly folded, SW-dipping, Permian Asitka Group siltstone and limestone and homogeneous Triassic Takla Group basalt. Southwest-dipping
194.0 ± 0.4-Ma Toodoggone Formation conglomerate, volcaniclastic, and epiclastic rocks overlie the granodiorite and Asitka
Group rocks. Minor Cu–Au–Mo mineralization is hosted by the immediate Takla Group basalt country rock, whereas low-tonnage
high-grade Cu zones occur beneath a 30-m-thick leached capping in supergene-altered granodiorite and in exotic positions in
overlying Toodoggone Formation conglomerate. Granodiorite has an intrusive contact with mineralized and altered Takla Group
basalt but displays a sheared contact with unmineralized and less altered Asitka Group siltstone. The North Block fault is
a deposit-scale, E-striking, steeply S-dipping normal fault that juxtaposes the granodiorite/basalt ore body against unmineralized
Asitka Group rocks. Younger NW- and NE-striking normal–dextral faults cut all rock types, orebodies, and the North Block fault
with displacements of up to 100 m and result in the graben-and-horst-style block faulting of the stratigraphy and ore body.
Both basalt and granodiorite host comparable vein sequence and alteration histories, with minor variations in hydrothermal
mineral assemblages caused by differing protolith chemistry. Early potassic alteration (and associated early-stage Cu ± Au ± Mo
mineralization) is partly replaced by phyllic and intermediate argillic alteration associated with main-stage Cu–Au–Mo mineralization.
Two main-stage veins have Re–Os molybdenite ages of 201.3 ± 1.2 and 201.1 ± 1.2 Ma. These mineralization ages overlap the
199.6 ± 0.6-Ma U–Pb zircon crystallization age for the Maple Leaf granodiorite. Late-stage pyrite-rich stringer veins and
related phyllic alteration assemblages are cut by anhydrite-rich, carbonate-rich, and chlorite veins. Fluids and metals associated
with early-, main-, and late-stage veins were probably derived principally from the same deep magma chamber as the Maple Leaf
granodiorite. These magmatic-derived fluids interacted with Asitka and Takla Group country rocks and possibly with meteoric
and metamorphic fluids prior to mineralization. 相似文献
2.
Diopside-rich, skarn-hosted, copper–gold ore derived primarily from carbonaceous metapelites at Mount Elliott forms a distinctive
member of the spectrum of Cu–Au–(Fe oxide) deposit styles in the Cloncurry district of the Paleoproterozoic to Mesoproterozoic
Mount Isa Block. The mine sequence is a package of carbonaceous metapelites and metagreywackes containing amphibolites derived
from tholeiitic basic rocks. A 40Ar–39Ar age spectrum with an extensive plateau-like segment at 1,510 ± 3 Ma from an actinolite associated with sulfides is taken
to represent the age of mineralization and is identical within error to the ages of most of the nearby batholithic granitoids.
The mine sequence is locally intruded by 1- to 10-m-thick late- to post-tectonic trachyandesite dykes, which were emplaced
during the hydrothermal activity that created the orebodies and have affinities with the regional high potassium “Eureka”
supersuite granitoids. Stable isotope data are consistent with dominantly magmatic fluids during mineralization and the regionally
distinctive skarn (Ca–Mg) and Cu–Au–Ni–Co–Te–Se (low Pb–Zn–Ag–Sb) chalcophile element associations may reflect a primitive
magmatic fluid source and/or leaching of these elements from country rocks. Mount Elliott is an unusual skarn deposit characterized
by pronounced early albitization (K–Fe–Mg depletion) of the host rocks succeeded by predominantly open-space deposition of
sodic diopside ± actinolite ± scapolite ± andradite ± magnetite ± sulfides ± apatite ± allanite ± tourmaline ± calcite. The
Ca–Fe–Mg(–Na)-rich (manganese-poor) chemistry was imposed from the fluid phase in the absence of carbonate-rich protoliths.
Immobile trace element (Ti, Zr, Nb) geochemistry shows that Mount Elliott skarns formed in both metasedimentary and mafic
metavolcanic host rocks, but the former are the main hosts of ore in upper and lower ore zones that represent most of the
resource. Banded skarns derived from a distinct calc-silicate/marble package at the nearby SWAN prospect have higher Nb/TiO2 and Zr/TiO2 ratios than the Mount Elliott metasediment-derived skarns, consistent with different provenance of the detrital components
in the two sequences. Medium- to coarse-grained massive skarn and skarn breccia in the Mount Elliott lower ore zone formed
in pelites and the trachyandesite dykes are the only intrusive rocks that could be genetically related to the mineralization
in the immediate vicinity of the orebodies.
Received: 1 September 1999 / Accepted: 28 September 2000 相似文献
3.
A set of sheeted quartz veins cutting 380 Ma monzogranite at Sandwich Point, Nova Scotia, Canada, provide an opportunity to
address issues regarding fluid reservoirs and genesis of intrusion-related gold deposits. The quartz veins, locally with arsenopyrite
(≤5%) and elevated Au–(Bi–Sb–Cu–Zn), occur within the reduced South Mountain Batholith, which also has other zones of anomalous
gold enrichment. The host granite intruded (P = 3.5 kbars) Lower Paleozoic metaturbiditic rocks of the Meguma Supergroup, well known for orogenic vein gold mineralization.
Relevant field observations include the following: (1) the granite contains pegmatite segregations and is cut by aplitic dykes
and zones (≤1–2 m) of spaced fracture cleavage; (2) sheeted veins containing coarse, comb-textured quartz extend into a pegmatite
zone; (3) arsenopyrite-bearing greisens dominated by F-rich muscovite occur adjacent the quartz veins; and (4) vein and greisen
formation is consistent with Riedel shear geometry. Although these features suggest a magmatic origin for the vein-forming
fluids, geochemical studies indicate a more complex origin. Vein quartz contains two types of aqueous fluid inclusion assemblages
(FIA). Type 1 is a low-salinity (≤3 wt.% equivalent NaCl) with minor CO2 (≤2 mol%) and has T
h = 280–340°C. In contrast, type 2 is a high-salinity (20–25 wt.% equivalent NaCl), Ca-rich fluid with T
h = 160–200°C. Pressure-corrected fluid inclusion data reflect expulsion of a magmatic fluid near the granite solidus (650°C)
that cooled and mixed with a lower temperature (400°C), wall rock equilibrated, Ca-rich fluid. Evidence for fluid unmixing,
an important process in some intrusion-related gold deposit settings, is lacking. Stable isotopic (O, D, S) analyses for quartz,
muscovite and arsenopyrite samples from vein and greisens indicate the following: (1) δ18Oqtz = +11.7‰ to 17.8‰ and δ18Omusc = +10.7‰ to +11.2‰; (2) δDmusc = −44‰ to−54‰; and (3) δ34Saspy = +7.8‰ to +10.3‰. These data are interpreted, in conjunction with fluid inclusion data, to reflect contamination of a magmatic-derived
fluid (d18OH2O {\delta^{{{18}}}}{{\hbox{O}}_{{{{\rm{H}}_{{2}}}{\rm{O}}}}} ≤ +10‰) by an external fluid (d18OH2O {\delta^{{{18}}}}{{\hbox{O}}_{{{{\rm{H}}_{{2}}}{\rm{O}}}}} ≥ +15‰), the latter having equilibrated with the surrounding metasedimentary rocks. The δ34S data are inconsistent with a direct igneous source based on other studies for the host intrusion (d18OH2O {\delta^{{{18}}}}{{\hbox{O}}_{{{{\rm{H}}_{{2}}}{\rm{O}}}}} = +5‰) and are, instead, consistent with an external reservoir for sulphur based on δ34SH2S data for the surrounding metasedimentary rocks. Divergent fluid reservoirs are also supported by analyses of Pb isotopes
for pegmatitic K-feldspar and vein arsenopyrite. Collectively the data indicate that the vein- and greisen-forming fluids
had a complex origin and reflect both magmatic and non-magmatic reservoirs. Thus, although the geological setting suggests
a magmatic origin, the geochemical data indicate involvement of multiple reservoirs. These results suggest multiple reservoirs
for this intrusion-related gold deposit setting and caution against interpreting the genesis of intrusion-related gold deposit
mineralization in somewhat analogous settings based on a limited geochemical data set. 相似文献
4.
The Mesoarchean Nuasahi chromite deposits of the Singhbhum Craton in eastern India consist of a lower chromite-bearing ultramafic
unit and an upper magnetite-bearing gabbroic unit. The ultramafic unit is a ∼5 km long and ∼400 m wide linear belt trending
NNW-SSE with a general north-easterly dip. The chromitite ore bodies are hosted in the dunite that is flanked by the orthopyroxenite.
The rocks of the ultramafic unit including the chromitite crystallized from a primitive boninitic magma, whereas the gabbro
unit formed from an evolved boninitic magma. A shear zone (10–75 m wide) is present at the upper contact of the ultramafic
unit. This shear zone consists of a breccia comprising millimeter- to meter-sized fragments of chromitite and serpentinized
rocks of the ultramafic unit enclosed in a pegmatitic and hybridized gabbroic matrix. The shear zone was formed late synkinematically
with respect to the main gabbroic intrusion and intruded by a hydrous mafic magma comagmatic with the evolved boninitic magma
that formed the gabbro unit. Both sulfide-free and sulfide-bearing zones with platinum group element (PGE) enrichment are
present in the breccia zone. The PGE mineralogy in sulfide-rich assemblages is dominated by minerals containing Pd, Pt, Sb,
Bi, Te, S, and/or As. Samples from the gabbro unit and the breccia zone have total PGE concentrations ranging from 3 to 116 ppb
and 258 to 24,100 ppb, respectively. The sulfide-rich assemblages of the breccia zone are Pd-rich and have Pd/Ir ratios of
13–1,750 and Pd/Pt ratios of 1–73. The PGE-enriched sulfide-bearing assemblages of the breccia zone are characterized by (1)
extensive development of secondary hydrous minerals in the altered parts of fragments and in the matrix of the breccia, (2)
coarsening of grain size in the altered parts of the chromitite fragments, and (3) extensive alteration of primary chromite
to more Fe-rich chromite with inclusions of chlorite, rutile, ilmenite, magnetite, chalcopyrite, and PGE-bearing chalcogenides.
Unaltered parts of the massive chromitite fragments from the breccia zone show PGE ratios (Pd/Ir = 2.5) similar to massive
chromitite (Pd/Ir = 0.4–6.6) of the ultramafic unit. The Ir-group PGE (IPGE: Ir, Os, Ru) of the sulfide-rich breccia assemblages
were contributed from the ultramafic–chromitite breccia. Samples of the gabbro unit have fractionated primitive mantle-normalized
patterns, IPGE depletion (Pd/Ir = 24–1,227) and Ni-depletion due to early removal of olivine and chromite from the primitive
boninitic magma that formed the ultramafic unit. Samples of the gabbro and the breccia zone have negative Nb, Th, Zr, and
Hf anomalies, indicating derivation from a depleted mantle source. The Cu/Pd ratios of the PGE-mineralized samples of the
breccia zone (2.0 × 103–3.2 × 103) are lower than mantle (6.2 × 103) suggesting that the parental boninitic magma (Archean high-Mg lava: Cu/Pd ratio ∼1.3 × 103; komatiite: Cu/Pd ratio ∼8 × 103) was sulfur-undersaturated. Samples of the ultramafic unit, gabbro and the mineralized breccia zone, have a narrow range
of incompatible trace element ratios indicating a cogenetic relationship. The ultramafic rocks and the gabbros have relatively
constant subchondritic Nb/Ta ratios (ultramafic rocks: Nb/Ta = 4.1–8.8; gabbro unit: Nb/Ta = 11.5–13.2), whereas samples of
the breccia zone are characterized by highly variable Nb/Ta ratios (Nb/Ta = 2.5–16.6) and show evidence of metasomatism. The
enrichment of light rare earth element and mobile incompatible elements in the mineralized samples provides supporting evidence
for metasomatism. The interaction of the ultramafic fragments with the evolved fluid-rich mafic magma was key to the formation
of the PGE mineralization in the Nuasahi massif. 相似文献
5.
陕西二台子铜金床钠长石碳酸（角砾）岩类特征及形成构造背景分析 总被引：7，自引：0，他引：7
从岩石学、矿物学、岩石化学、地球化学、稀土元素等方面研究了二台子铜金矿内长石炭酸（角砾）岩类地质地球化学特征。晚泥盆世－石炭纪,在区域幔羽构造作用下,深部热流体沿先存在构造通道上升进入镇安二台子三级热水沉积盆地之中,形成了石英重晶石炭酸角砾岩、碳酸角砾岩、复成分角砾岩、钠长岩、钠长石碳酸岩,受同性断裂及层位控制明显,并构成了金的矿源层及普遍金矿化。燕山期,具有幔源特征的深部含矿热流体在北东、北西向 相似文献
6.
The Wild Bight Group (WBG) and South Lake Igneous Complex (SLIC) together comprise one of the Ordovician accreted oceanic
terranes of the central mobile belt of the Newfoundland Appalachians. Combined detailed mapping, geochemistry, Sm-Nd isotopic
studies and U-Pb geochronology have shown that sheeted dykes and hornblende diorite and tonalite plutons of the SLIC are genetically
related to a discrete package of volcanic rocks in the WBG. These igneous rocks are geochemically, isotopically and temporally
distinct from volcanic rocks in the rest of the WBG. Plutonic rocks of the SLIC range in age from 486 ± 3 Ma to 489 ± 3 Ma,
and a cross-cutting gabbro dyke gives a minimum age of 486 ± 4 Ma for the related volcanic sequence. Volcanic rocks in the
rest of the WBG sequence are predominantly younger than 472 ± 3 Ma. The older volcanic sequence of the WBG and the SLIC occur
as fault-bounded packages interleaved within the younger WBG sequence. A conformable stratigraphic relationship between the
older and younger sequences of the WBG has not been demonstrated. The mafic rocks of the older package include boninites and
low-Ti, high-Mg tholeiitic island arc basalts which are interpreted to be genetically related, and normal island arc tholeiites
(IAT). The high-Mg mafic rocks are interpreted to have formed in an extensional setting during subduction zone initiation,
and the normal IAT are thought to represent stabilisation of the volcanic front. The associated high-Si, low-K rhyolite and
tonalite are interpreted to be the products of secondary melting at the base of thickened early arc crust. Sm-Nd isotopic
compositions indicate that the characteristic trace element signature of the boninites developed at or near their time of
generation and was not a long lived characteristic of the source region. The boninites and low-Ti tholeiites are interpreted
to have originated from a similar source, which was metasomatized by different subduction-related components. Apparent decoupling
of Sm-Nd geochemical and isotopic compositions suggests that these very depleted rocks may be recording the effect of subduction
zone processes not yet fully understood.
Received: 31 October 1997 / Accepted: 6 May 1998 相似文献
7.
8.
Intrusion-related gold deposits associated with tungsten-tin provinces 总被引：22，自引：0，他引：22
J. F. H. Thompson R. H. Sillitoe T. Baker J. R. Lang J. K. Mortensen 《Mineralium Deposita》1999,34(4):323-334
An under-recognized and economically important class of intrusion-related gold deposits, which occur within magmatic provinces
best known for tungsten and/or tin mineralization, is described with reference to seven major deposits (Fort Knox, Mokrsko,
Salave, Vasilkovskoe, Timbarra, Kidston and Kori Kollo). These gold deposits contain a metal suite that includes some combination
of bismuth, tungsten, arsenic, tin, molybdenum, tellurium and antimony, and contrasts with that found in the more widely-developed
gold-rich porphyry copper and related deposits. The gold deposits associated with tungsten and/or tin provinces are located
in cratonic margins, in a landward or back-arc position relative to continental margin arcs (where recognized), or within
continental collisional settings. The deposits are related genetically to felsic domes, stocks or plutons of intermediate
oxidation state, both magnetite- and ilmenite-series magmas are represented. The intrusion-hosted gold deposits are most commonly
of sheeted vein/veinlet type, although greisen-like, disseminated and breccia deposits are also described. Gold may also be
concentrated more distally (1–3 km) with respect to the intrusions, where deposits may be of skarn, disseminated replacement
or vein types. K-feldspar, albite and/or sericitic alteration assemblages, commonly including carbonate, accompany the gold
mineralization. In sheeted vein deposits, alteration is normally restricted to narrow envelopes around veins, whereas more
pervasive alteration occurs in greisen-like, disseminated and shallow (<3 km) deposits. The gold mineralization is commonly
present with low total sulphide contents (<3%), mainly pyrite and lesser arsenopyrite. In several deposits, bismuth minerals
are closely associated with gold, and bismuth-gold and tellurium-gold correlations exist. Most deposits contain tungsten,
tin, molybdenum and antimony, although generally these do not correlate with gold; tungsten and molybdenum concentrations
may increase with depth or may occur in separate zones. Base metals generally are present in minor amounts (e.g. <100 ppm
Cu). The distinct spatial association with felsic intrusions, combined with the consistent metal signature, suggests a magmatic-hydrothermal
origin. Fluid inclusions studies indicate the presence of high-salinity fluids in some deposits, and low-salinity and carbonic
fluids in most deposits, similar to the composition of fluids in intrusion-related tungsten deposits. Variations in mineralization
style largely reflect depth of formation and location relative to the intrusive centre. Several deposits in this class contain
>100 tonnes (3 million oz) of gold, thereby highlighting the gold potential of intrusion-related deposits beyond the more
traditionally explored gold and copper provinces in arc terranes.
Received: 13 March 1998 / Accepted 14 January 1999 相似文献
9.
黑龙江先锋北山金矿床火山岩地球化学特征、LA-ICP-MS锆石U-Pb定年及地质意义 总被引：2，自引：0，他引：2
黑龙江省先锋北山金矿床地处完达山造山带西南段,矿体主要赋存在流纹岩、岩屑晶屑凝灰岩和流纹质角砾岩中。文章系统研究了与成矿密切相关的火山岩的地球化学特征,同时,对其进行了LA-ICP-MS锆石U-Pb测年。与成矿相关的火山岩(流纹岩、岩屑晶屑凝灰岩、流纹质角砾岩)表现出高硅、富碱,贫铝、镁、钙的特征,属碱性系列岩石;具有弱的Eu负异常;富集大离子亲石元素K、Rb、Th等;亏损高场强元素Ta、Nb、P、Ti等。同时,Ba、Sr、Eu等元素亦表现为亏损,具有典型的同碰撞环境的地球化学特征。LA-ICP-MS锆石U-Pb测年显示,流纹岩、流纹质角砾岩和石英闪长玢岩的206Pb/238U谐和年龄分别为(116.98±0.47)Ma、(116.98±0.42)Ma和(108.48±0.99)Ma。结合矿区侵入接触关系,限定先锋北山金矿床的形成时间介于(116.98±0.47)Ma~(108.48±0.99)Ma,即早白垩世晚期。该矿床的形成与太平洋板块的俯冲和佳木斯与完达山地块的拼合有着密切的关系,系古太平洋板块构造体制由挤压变为伸展背景下的产物。 相似文献
10.
Gossan Hill is an Archean (∼3.0 Ga) Cu–Zn–magnetite-rich volcanic-hosted massive sulfide (VHMS) deposit in the Yilgarn Craton
of Western Australia. Massive sulfide and magnetite occur within a layered succession of tuffaceous, felsic volcaniclastic
rocks of the Golden Grove Formation. The Gossan Hill deposit consists of two stratigraphically separate ore zones that are
stratabound and interconnected by sulfide veins. Thickly developed massive sulfide and stockwork zones in the north of the
deposit are interpreted to represent a feeder zone. The deposit is broadly zoned from a Cu–Fe-rich lower ore zone, upwards
through Cu–Zn to Zn–Ag–Au–Pb enrichment in the upper ore zone. New sulfur isotope studies at the Gossan Hill deposit indicate
that the variation is wider than previously reported, with sulfide δ34S values varying between −1.6 and 7.8‰ with an average of 2.1 ± 1.4‰ (1σ error). Sulfur isotope values have a broad systematic
stratigraphic increase of approximately 1.2‰ from the base to the top of the deposit. This variation in sulfur isotope values
is significant in view of typical narrow ranges for Archean VHMS deposits. Copper-rich sulfides in the lower ore zone have
a narrower range (δ34S values of −1.6 to 3.4‰, average ∼1.6 ± 0.9‰) than sulfides in the upper ore zone. The lower ore zone is interpreted to have
formed from a relatively uniform reduced sulfur source dominated by leached igneous rock sulfur and minor magmatic sulfur.
Towards the upper Zn-rich ore zone, an overall increase in δ34S values is accompanied by a wider range of δ34S values, with the greatest variation occurring in massive pyrite at the southern margin of the upper ore zone (−1.0 to 7.8‰).
The higher average δ34S values (2.8 ± 2.1‰) and their wider range are explained by mixing of hydrothermal fluids containing leached igneous rock
sulfur with Archean seawater (δ34S values of 2 to 3‰) near the paleoseafloor. The widest range of δ34S values at the southern margin of the deposit occurs away from the feeder zone and is attributed to greater seawater mixing
away from the central upflow zone.
Received: 10 June 1999 / Accepted: 28 December 1999 相似文献
11.
Pongkor (west Java, Indonesia): a Pliocene supergene-enriched epithermal Au-Ag-(Mn) deposit 总被引：2，自引：0，他引：2
J. P. Milési E. Marcoux T. Sitorus M. Simandjuntak J. Leroy L. Bailly 《Mineralium Deposita》1999,34(2):131-149
The Pongkor gold-silver epithermal deposit with reserves of at least 98 tonnes of gold and 1026 tonnes of silver, average
grades 16.4 g/t Au and 171.2 g/t Ag is one of the most recent and largest gold and silver discoveries in Indonesia, proven
within a short period (1988–1991). 40Ar/39Ar dating on adularia samples give an age of 2.05 ± 0.05 Ma. The deposit is of the low-sulfidation epithermal type and consists
of four main mineralized quartz veins located close to the internal rim of a volcano-tectonic depression (caldera). This resulted
from an explosive ignimbritic eruption that produced pyroclastic flows and accretionary lapilli with rare intercalations of
epiclastic rocks. This volcanic unit unconformably overlies Miocene subaqueous volcanic andesitic rocks with interbedded epiclastic
rocks. The mineralized bodies are thick (average 4.2 m), steeply dipping, quartz-carbonate-adularia veins with a very low
sulfide content (<0.5 wt.%). Their genesis is related to an extensional episode within a tectonic corridor showing NW-SE and
NNE-SSW conjugate strike-slip faults, the major vein being located on the inner rim of the caldera. The vein fill reveals
four successive stages of deposition marked by a specific facies: (1) carbonate-quartz breccia with dominant quartz and calcite
and minor kutnahorite, rhodochrosite, and rhodonite (CQ facies), (2) a network of banded quartz and former carbonate transformed
into manganese oxides through supergene alteration (MOQ facies), (3) banded opaline milky quartz (BOQ facies), and (4) grey,
locally banded, sulfide-rich quartz breccia cutting all the other types (GSQ facies). Adularia was deposited at the same time
as the quartz. The mineralogy and internal structures of the veins (crustiform banding, vugs, collapse breccia) clearly indicate
a dilational context, which is common in low-sulfidation epithermal systems. Gold and silver grades, as well as sulfide mineral
abundances, increase steadily through stages 1 to 4, locally reaching 1 kg/t in the GSQ facies. The sulfides are dominated
by pyrite, accompanied by common acanthite-aguilarite, polybasite-pearceite and electrum in which the gold content ranges
from 48 to 74 wt.%. Sphalerite, galena, chalcopyrite and hessite are fairly rare, although present within the CQ facies. The
fluid inclusions of the four facies show homogenization temperatures ranging from 150 to 382 °C, indicating boiling of a hydrothermal
fluid with an initial temperature of around 205 °C; no marked difference is seen in the GSQ facies, which has the highest
gold content. Salinities are low, generally below 1 wt.% eq. NaCl. Lead isotope compositions of the associated volcanic rocks
and the mineralization are very similar, 206Pb/204Pb between 18.706 and 18.814␣and between 18.744 and 18.801 respectively, demonstrating a genetic link between the Pliocene
volcanism and the auriferous hydrothermal activity. The isotopic signature suggests that the source of the mineralization
and associated volcanic rocks is an underlying ancient continental crust that melted and remobilized during the Pliocene volcanic
and hydrothermal events. These conclusions seem applicable to the entire Bayah Dome. The existence of both a tectonic corridor
and a caldera favoured channelling of the hydrothermal fluids and the deposition of primary ore in the veins. Late intense
weathering of the ore deposit, to depths of 250 m below the surface, has given rise to manganese oxide layers, limonite zones,
and silver micronuggets within the veins, as well as to gold enrichment.
Received: 25 June 1997 / Accepted: 10 March 1998 相似文献
12.
Summary The Tuvatu gold–telluride prospect is one of several epithermal gold systems along the >250 km northeast trending Viti Levu
lineament, Fiji, which are genetically associated with alkalic magmatism. Vein structures contain a variety of sulfides, native
elements, sulfosalts, and tellurides. Calaverite is intimately associated with various vanadium-bearing minerals: roscoelite,
karelianite, vanadian muscovite, Ti-free nolanite, vanadian rutile, schreyerite, and an unnamed vanadium silicate. Thermodynamic
calculations for the systems V–Al–K–Si–O–H (Cameron, 1998) and Au–Te–Cl–S–O–H at estimated conditions of formation of the telluride-native gold stage at Tuvatu (∼250 °C, ΣAu
= 1 ppb, ΣTe = 1 ppb, ΣS = 0.001 m, ΣV = 0.0001 m, and aK = 0.01), show that the stability fields of calaverite, roscoelite, and karelianite converge in pH-fO2 space near the hematite–magnetite buffer and at neutral to slightly acid conditions. Thermodynamic and textural data suggest
that these minerals were deposited together at Tuvatu and likely explain the common coexistence of roscoelite and calaverite
in epithermal gold systems elsewhere. The presence of magnetite with up to 0.7 wt.% V2O3 in the Navilawa Monzonite is consistent with the derivation of V from the alkalic intrusive rocks, which are also considered
to be the source of Au and Te in the Tuvatu deposit. 相似文献
13.
Synchronous deformation and hydrothermal activity in the shear zone hosted high-sulphidation Au-Cu deposit at Peak Hill, NSW, Australia 总被引：1，自引：0，他引：1
A. Allibone 《Mineralium Deposita》1998,33(5):495-512
Altered and mineralised rocks at Peak Hill, are confined to a 300–500 m wide, north-south striking, steeply dipping, shear
zone that is flanked by the Mingelo Volcanics along its western side, and Cotton Formation siltstones along its eastern side.
This shear zone is defined by extensive zones of cataclasite and strongly foliated micaceous schists in marked contrast to
the largely undeformed nature of the adjacent rocks. Advanced argillic assemblages (quartz-kaolinite-pyrite ± alunite ± illite)
occur throughout the core of the Peak Hill deposit. Propylitic assemblages, including albite, quartz, interlayered chlorite-smectite,
illite and ankerite, and a narrow discontinuous zone of argillic (quartz-illite-pyrite) alteration are developed in the Mingelo
Volcanics along the western side of the deposit. Propylitic, argillic and advanced argillic assemblages are overprinted by
an internally zoned phase of phyllosilicate alteration that grades inwards from a peripheral sericite-clay-chlorite assemblage,
through phyllic assemblages (muscovite/illite-pyrite ± paragonite) to a pyrophyllite-pyrite ± diaspore ± andalusite altered
core. Au-Cu mineralisation is hosted by barite-pyrite veins that cut the advanced argillic assemblage, but pre-date the phyllosilicate-dominated
alteration. Native Au (lacking Ag), calaverite, Te-rich tennantite-tetrahedrite (goldfieldite), chalcopyrite, covellite and chalcocite occur in the barite-pyrite veins. No ore-bearing minerals were detected in any of
the alteration assemblages. The total gold content of the Peak Hill deposit is currently 720 K ounces and this includes 100 K
ounces of unmined reserves. Within the shear zone phyllosilicate minerals are developed in strain shadows and partly define
the stretching lineation associated with dip-slip movement. The zonation within the phyllosilicate assemblages mimics the
geometry of bends in the shear zone and minor internal structures. These textures indicate that the phyllosilicate alteration
developed synchronous with movement on the shear zone. Earlier advanced argillic alteration and mineralisation are developed
in rocks derived from both sides of the shear zone. Hydrothermal activity associated with the earlier advanced argillic alteration
was therefore either synchronous with juxtaposition of these distinct rock units, or occurred during a later phase of movement
on the shear zone. Cross-cutting fibrous textures in the auriferous barite-pyrite veins indicate that repeated fracturing
of the advanced argillic altered rocks accompanied development of successive generations of auriferous veins. Concentrations
of auriferous veins are localised in steeply plunging shoots that are oriented parallel to the stretching lineation in the
shear zone. These features all indicate movement on the host shear zone accompanied each phase of hydrothermal activity in
the Peak Hill deposit. The location, alteration zonation and distribution of mineralised veins within the deposit are intimately
controlled by deformation on the host shear zone synchronous with hydrothermal activity. The development of high-sulphidation
hydrothermal systems synchronous with deformation along brittle-ductile shear zones is a predictable consequence of intrusive
activity during deformation in areas characterised by a high geothermal gradient. The close relationship between tectonism
and hydrothermal activity indicates that these deposits are likely to be located in the vicinity of regional-scale shear zones.
Deposits are likely to be aligned parallel to the regional-scale structural “grain” and restricted to areas of conspicuous
deformation as is the case at Peak Hill (and Temora, NSW). Aluminous alteration zones concentrated in the vicinity of regional-scale
structures in the Carolina Slate Belt may be a further example of this style of hydrothermal activity.
Received: 30 September 1996 / Accepted: 28 August 1997 相似文献
14.
松辽盆地东南隆起区下白垩统营城组三段火山岩岩性、岩相序列 总被引：1，自引：0，他引：1
通过大比例尺野外岩性岩相填图、掌子面二维岩性岩相描述和详细岩矿鉴定,研究营城组三段内幕。本区营三段自下而上岩性序列表现为2个中基性到中酸性的火山岩旋回：①下部为石英安山岩、安山岩、安山质集块熔岩、安山质集块岩、安山质角砾岩和安山质角砾凝灰岩,向上过渡为砂质凝灰岩和英安质凝灰熔岩;②上部为玄武安山岩和玄武质集块熔岩,向上过渡为英安岩、珍珠岩、英安岩、英安质凝灰熔岩、英安质沉凝灰岩和英安岩。旋回①岩相纵向序列：溢流相下部亚相、火山通道相火山颈亚相、爆发相空落亚相、火山沉积相再搬运亚相、爆发相热碎屑流亚相。旋回②岩相纵向序列：溢流相上部亚相和下部亚相、火山通道相火山颈亚相、溢流相下部亚相、侵出相内带亚相、溢流相下部亚相、爆发相热碎屑流亚相、火山沉积相再搬运亚相、溢流相下部亚相。营三段火山岩发育于松辽盆地断陷末期,是盆地断陷转为坳陷过程的重要岩石记录。 相似文献
15.
长安金矿是近年来在哀牢山金矿带发现的另一种独特类型的金矿床。通过对前人研究成果和新获得的深边部勘查资料的综合研究,认为长安金矿主矿体呈似层状、透镜状,向NE陡倾产于NNW向的F6断层破碎带东亚带砂泥质构造岩中,矿体走向及倾向上具有膨大缩小、舒缓波状变化特征;F6断裂为最主要的控矿构造;断层破碎带东亚带中砂泥质碎裂岩、角砾岩金矿化较强,西亚带白云质构造岩金矿化微弱;喜山期辉绿岩、煌斑岩、正长斑岩、细晶正长岩等岩浆侵入活动与金成矿关系较为密切,提供了重要成矿流体。砂泥质碎裂岩、角砾岩和侵入岩脉与围岩接触带、断裂交汇处对金成矿有利,受硅化、黄铁矿化、毒砂化等多种蚀变叠加的部位,易形成工业金矿体。 相似文献
16.
Geology and geochemistry of telluride-bearing Au deposits in the Pingyi area, Western Shandong, China 总被引：2，自引：0，他引：2
Summary Telluride-bearing gold deposits of the Pingyi area, western Shandong, China, are located on the southeastern margin of the
North China Craton. There are two main types of deposits: (i) mineralized cryptoexplosive breccia, e.g., Guilaizhuang; and
(ii) stratified, finely-disseminated mineralization hosted in carbonate rocks, e.g., Lifanggou and Mofanggou deposits. In
Guilaizhuang, the cryptoexplosive breccia is formed within rocks of the Tongshi complex and Ordovician dolomite. The mineralization
is controlled by an E–W-trending listric fault. Stratified orebodies of the Lifanggou and Mofanggou deposits are placed along
a NE-trending, secondary detachment zone. They are hosted within dolomitic limestone, micrite and dolomite of the Early-Middle
Cambrian Changqing Group. The mineralization in the ore districts is considered to be related to the Early Jurassic Tongshi
magmatic complex that formed in a continental arc setting on the margin of the North China Craton. The host rocks are porphyritic
and consist predominantly of medium- to fine-grained diorite and pyroxene (hornblende)-bearing monzonite. SHRIMP U–Pb zircon
dating of diorites give a 206Pb/238U weighted mean age of 175.7 ± 3.8 Ma. This is interpreted as representing the crystallization age of the Tongshi magmatic
complex. Considering the contact relationships between the magmatic and host sedimentary rocks, as well as the genetic link
with the deposits, we conclude that this age is relevant also for the formation of mineralization in the Pingyi area. We hence
consider that the deposits formed in the Jurassic. The principal gold minerals are native gold, electrum and calaverite. Wall-rock
alteration comprises pyritization, fluoritization, silicification, carbonatization and chloritization. Fluid inclusion studies
indicate that all the analyzed inclusions are of two-phase vapor–liquid NaCl–H2O type. Homogenization temperatures of the fluid inclusions vary from 103 °C to 250 °C, and the ice melting temperatures range
from −2.5 °C to −13.5 °C, corresponding to a salinity range of 4.65 to 17.26 wt.% NaCl equiv. The δ34S values of pyrite associated with gold mineralization exhibit a narrow range of −0.71 to + 2.99‰, implying that the sulfur
was probably derived from the mantle and/or dioritic magma. The δ13CPDB values of the fluid inclusions in calcite range from −7.3 to 0.0‰. The δ18OSMOW values of vein quartz and calcite range from 11.5 to 21.5‰, corresponding to δ18Ofluid values of −1.1 to 10.9‰; δD values of the fluid inclusions vary between −70 and −48‰. The isotope data for all three deposits
suggest mixing of ore-forming fluids derived from the mantle and/or magma with different types of fluids at shallow levels.
Pressure release and boiling of the fluids, as well as fluid-rock interaction (Lifanggou and Mofanggou) and mixing of magmatically-derived
fluids with meteoritic waters (Guilaizhuang) played an important role in the ore-forming processes. 相似文献
17.
勐满金矿床位于云南省勐海县境内,地处临沧-景洪褶皱束之临沧-澜沧复背斜南部,截至2005年探明金矿资源量17t,主矿体属于地表红土型氧化矿,平均品位为0.60×10-6。文章基于对勐满金矿床矿区内新元古界曼来组片岩和中侏罗统花开左组碎屑岩及矿区外围东部的临沧花岗岩的LA-ICP-MS锆石U-Pb年龄测定,探讨了曼来组片岩和花开左组碎屑岩地层的物质来源,追溯母岩的物质源区,并结合矿区普遍发育的硅化岩和硅质脉体的地球化学特征,分析了金成矿的物质来源。勐满金矿床曼来组中主要碎屑锆石年龄为(957.0±9.8)Ma,属新元古代早青白口纪;中侏罗系花开左组主要碎屑锆石年龄为(224.2±2.8)Ma,与临沧花岗岩基中2件黑云母二长花岗岩的年龄(分别为(228.7±2.8)Ma和(229.4±2.0)Ma)一致,表明花开左组地层的物质来源可能与临沧花岗岩有关。微量元素测试结果显示,矿区硅化岩与硅质脉体具有相似的稀土元素配分模式与微量元素组成,均表现为富集U、Th、Pb等大离子亲石元素,亏损Zr、Hf、Nb、Ta等高场强元素,轻稀土元素明显富集,重稀土元素亏损,中-弱的Eu负异常,Ce异常不明显,与矿区围岩及临沧花岗岩体南部的黑云母花岗岩具有相似的变化趋势。硅化岩稀土元素总量为42.3×10-6~311.0×10-6,平均为131.8×10-6;硅质脉体稀土元素总量为5.0×10-6~280×10-6,平均为56.8×10-6,显示硅化岩相对于硅质脉体具有更高的稀土元素总量。硅质脉体((La/Yb)N为4.3~133.4,平均36.7)相对于硅化岩((La/Yb)N为2.1~26,平均为8.5)具有更高的轻、重稀土元素分馏特征。硅化岩的地球化学特征变化介于围岩与硅质脉之间,表明硅化岩既继承了围岩特征,又有经热泉活动改造的痕迹。综合锆石年代学结果与沉积物源分析,认为矿区花开左组砂岩主要为临沧岩体经受风化搬运沉积的产物,曼来组向花开左组提供金的量不足以形成花开左组中的碎屑岩型矿体,热泉活动产生的流体是金成矿的另一重要物质来源,同时是导致金后期富集的重要因素。据此推断,花开左组是赋矿层位,而并非矿源层。结合低硫型矿床标志性矿物冰长石的出现,提出勐满金矿属于典型的与热泉活动有关的低硫型浅成低温热液金矿。 相似文献
18.
19.
The breccia-hosted epithermal gold–silver deposit of Chah Zard is located within a high-K, calc-alkaline andesitic to rhyolitic
volcanic complex in the central part of the Urumieh-Dokhtar Magmatic Arc (UDMA), west central Iran. The total measured resource
for Chah Zard is ∼2.5 million tonnes of ore at 12.7 g/t Ag and 1.7 g/t Au (28.6 t Ag, 3.8 t Au), making it one of the largest
epithermal gold deposits in Iran. Magmatic and hydrothermal activity was associated with local extensional tectonics in a
strike-slip regime formed in transtensional structures of the Dehshir-Baft strike-slip fault system. The host rocks of the
volcanic complex consist of Eocene sedimentary and volcanic rocks covered by Miocene sedimentary rocks. LA-ICP–MS U–Pb zircon
geochronology yields a mean age of 6.2 ± 0.2 Ma for magmatic activity at Chah Zard. This age represents the maximum age of
mineralization and may indicate a previously unrecognized mineralization event in the UDMA. Breccias and veins formed during
and after the waning stages of explosive brecciation events due to shallow emplacement of rhyolite porphyry. Detailed systematic
mapping leads to the recognition of three distinct breccia bodies: volcaniclastic breccia with a dominantly clastic matrix;
gray polymict breccia with a greater proportion of hydrothermal cement; and mixed monomict to polymict breccia with clay matrix.
The polymictic breccias generated bulk-mineable ore, whereas the volcaniclastic breccia is relatively impermeable and largely
barren. Precious metals occur with sulfide and sulfosalt minerals as disseminations, as well as in the veins and breccia cements.
There is a progression from pyrite-dominated (stage 1) to pyrite-base metal sulfide and sulfosalt-dominated (stages 2 and
3) to base metal sulfide-dominated (stage 4) breccias and veins. Hydrothermal alteration and deposition of gangue minerals
progressed from illite-quartz to quartz-adularia, carbonate, and finally gypsum-dominated assemblages. Free gold occurs in
stages 2 and 4, principally intergrown with pyrite, quartz, chalcopyrite, galena, sphalerite, and Ag-rich tennantite–tetrahedrite,
and also as inclusions in pyrite. High Rb/Sr ratios in ore-grade zones are closely related to sericite and adularia alteration.
Positive correlations of Au and Ag with Cu, As, Pb, Zn, Sb, and Cd in epithermal veins and breccias suggest that all these
elements are related to the same mineralization event. 相似文献