Apatite Texture, Composition, and O-Sr-Nd Isotope Signatures Record Magmatic and Hydrothermal Fluid Characteristics at the Black Mountain Porphyry Deposit, Philippines

2021 ◽  
Author(s):  
Ming Jian Cao ◽  
Noreen J. Evans ◽  
Pete Hollings ◽  
David R. Cooke ◽  
Brent I.A. McInnes ◽  
...  
Keyword(s):  
Phase Separation ◽  
High Temperature ◽  
Oxygen Isotope ◽  
Hydrothermal Alteration ◽  
Hydrothermal Fluid ◽  
Isotope Composition ◽  
Hydrothermal Fluids ◽  
Nd Isotope ◽  
O Isotope ◽  
Black Mountain

Abstract The trace elemental and isotopic signatures in apatite can be modified during hydrothermal alteration. This study investigates the suitability of apatite as an indicator of the source, chemistry, and evolution of magma and hydrothermal fluids. In situ textural, elemental, and O-Sr-Nd isotope analyses were performed on apatite in thin sections, from fresh and propylitically altered pre- and synmineralized dioritic porphyries from the Black Mountain porphyry Cu deposit in the Philippines. All studied apatite crystals have similar subhedral to euhedral shapes and are homogeneous in the grayscale in backscattered electron images. In cathodoluminescence images, the apatite in fresh and altered rocks displays yellow to yellow-green and green to brown luminescence, respectively. Apatite in fresh rocks has a higher Cl and Mn content, and lower Fe, Mg, Sr, Pb, and calculated XOH-apatite, compared to apatite in altered rocks. The content of F, rare earth elements (REEs), Y, U, Th, and Zr, and the Sr-Nd isotope signatures of apatite from fresh and altered rocks are similar in all apatite grains (87Sr/86Sr = 0.7034–0.7042 vs. 0.7032–0.7043, εNd(t) = 5.3–8.0 vs. 5.1–8.4). The X-ray maps and elemental and oxygen isotope signatures across individual apatite crystals are typically homogeneous in apatite from both fresh and altered rocks. The distinct luminescence colors, coupled with distinct mobile element compositions (Cl, OH, Mn, Mg, Fe, Sr, Pb), indicate modification of primary magmatic apatite during interaction with hydrothermal fluids. The similarities in Sr isotope ratios (87Sr/86Sr = 0.7032–0.7043) but slight differences in O isotope signatures (δ18O = 6.0 ± 0.3‰ vs. 6.6 ± 0.3‰) in apatite from fresh and altered rocks are consistent with the magma and hydrothermal fluids having the same source and suggest significant phase separation in the hydrothermal fluids given that 18O preferentially fractionates into the residual liquid relative to 16O during phase separation. The similarity of immobile element (REE, Y, U, Th, and Zr) contents in both populations of apatite, consistency of textures and Nd isotope compositions, and absence of obvious dissolution-reprecipitation features all suggest that altered apatite retains some magmatic characteristics. The apatite in fresh rocks has oxygen isotope compositions similar to that of zircons from the same sample (δ18O = 5.9 ± 0.3‰), indicating little to no oxygen isotope fractionation between zircon and apatite and that apatite can be a good proxy for the oxygen isotope composition of the magma. Based on the Cl contents of the magmatic and replacement apatite, and assuming their equilibrium with high-temperature magma fluid and replacement hydrothermal fluid, respectively, the calculated Cl content of the early magmatic fluid and the later replacement fluid can be estimated to be 6.4 to 15.1 wt % and ~0.25 ± 0.03 wt %, respectively. This indicates a depletion of Cl from the early high-temperature fluid to the replacement fluid, consistent with phase separation. This study demonstrates that cathodoluminescence, elemental compositions (such as Cl, Mn, Mg, Fe, Sr, Pb) and Sr-O isotope signatures in apatite can be modified during hydrothermal alteration, whereas other components (REE, Y, U, Th, and Zr) and the Nd isotope composition are preserved. These features can be used to constrain the origin, chemistry, and evolution of the primary magma and ore-forming hydrothermal fluids.

Formation of coagulated colloidal silica in high-temperature mineralizing fluids

2002 ◽  
Vol 66 (4) ◽  
pp. 547-553 ◽  
Author(s):  
B. J. Williamson ◽  
J. J. Wilkinson ◽  
P. F. Luckham ◽  
C. J. Stanley
Keyword(s):  
High Temperature ◽  
Hydrothermal Fluid ◽  
Colloidal Silica ◽  
Fluid Transport ◽  
Experimental Studies ◽  
Hydrothermal Fluids ◽  
Ore Formation ◽  
Colloidal Gel ◽  
Material Forming ◽  
Mineralizing Fluids

AbstractRecent experimental studies have suggested that colloidal silica can form in high-T (300 to >700°C) hydrothermal fluids (Wilkinson et al., 1996). Natural evidence in support of this was found by Williamson et al. (1997) who proposed a colloidal (gel) silica origin for <50 μm irregularly-shaped inclusions of quartz contained in greisen topaz from southwest England. Confocal and microprobe studies, presented here, strengthen this argument although rather than forming a gel in the hydrothermal fluid, it is suggested that the colloidal silica aggregated as a viscous coagulated colloid, with much of its volume (<10 to 30 vol.%) consisting of metal (mainly Fe) -rich particles. This is evident from the largely solid nature of metal-rich shrinkage bubbles contained at the margins of the inclusions of quartz which shows that the material forming the inclusions contained much less liquid than would be expected in a silica gel. These findings may have important implications for models of ore formation since the precipitation of a coagulated colloid could inhibit hydrothermal fluid transport and cause co-deposition of silica and entrained ore-forming elements. The mode of formation of the colloidal silica and further implications of the study are discussed.

scholarly journals A New Insight Into Seawater-Basalt Exchange Reactions Based on Combined δ18O—Δ′17O—87Sr/86Sr Values of Hydrothermal Fluids From the Axial Seamount Volcano, Pacific Ocean

2021 ◽  
Vol 9 ◽  
Author(s):  
D. O. Zakharov ◽  
R. Tanaka ◽  
D. A. Butterfield ◽  
E. Nakamura
Keyword(s):  
Phase Separation ◽  
Pacific Ocean ◽  
Hydrothermal Fluids ◽  
Exchange Reactions ◽  
Isotope Shifts ◽  
Individual Site ◽  
Dual Porosity Model ◽  
O Isotope ◽  
Axial Seamount ◽  
Isotope Systematics

The δ18O values of submarine vent fluids are controlled by seawater-basalt exchange reactions, temperature of exchange, and to a lesser extent, by phase separation. These variations are translated into the δ18O values of submarine hydrothermal fluids between ca. 0 and + 4‰, a range defined by pristine seawater and equilibrium with basalt. Triple oxygen isotope systematics of submarine fluids remains underexplored. Knowing how δ17O and δ18O change simultaneously during seawater-basalt reaction has a potential to improve i) our understanding of sub-seafloor processes and ii) the rock-based reconstructions of ancient seawater. In this paper, we introduce the first combined δ17O-δ18O-87Sr/86Sr dataset measured in fluids collected from several high-temperature smoker- and anhydrite-type vent sites at the Axial Seamount volcano in the eastern Pacific Ocean. This dataset is supplemented by measurements of major, trace element concentrations and pH indicating that the fluids have reacted extensively with basalt. The salinities of these fluids range between 30 and 110% of seawater indicating that phase separation is an important process, potentially affecting their δ18O. The 87Sr/86Sr endmember values range between 0.7033 and 0.7039. The zero-Mg endmember δ18O values span from -0.9 to + 0.8‰, accompanied by the Δ′17O0.528 values ranging from around 0 to −0.04‰. However, the trajectory at individual site varies. The endmember values of fluids from focused vents exhibit moderate isotope shifts in δ′18O up to +0.8‰, and the shifts in Δ′17O are small, about −0.01‰. The diffuse anhydrite-type vent sites produce fluids that are significantly more scattered in δ′18O—Δ′17O space and cannot be explained by simple isothermal seawater-basalt reactions. To explain the observed variations and to provide constraints on more evolved fluids, we compute triple O isotope compositions of fluids using equilibrium calculations of seawater-basalt reaction, including a non-isothermal reaction that exemplifies complex alteration of oceanic crust. Using a Monte-Carlo simulation of the dual-porosity model, we show a range of possible simultaneous triple O and Sr isotope shifts experienced by seawater upon reaction with basalt. We show the possible variability of fluid values, and the causal effects that would normally be undetected with conventional δ18O measurements.

Oxygen isotope evidence for major fluid flow along the contact zone of the Rum ultrabasic intrusion

1992 ◽  
Vol 129 (2) ◽  
pp. 243-246 ◽  
Author(s):  
R. C. Greenwood ◽  
A. E. Fallick ◽  
C. H. Donaldson
Keyword(s):  
Fluid Flow ◽  
Oxygen Isotope ◽  
Contact Zone ◽  
Hydrothermal Alteration ◽  
Low Temperatures ◽  
Hydrothermal Fluids ◽  
Major Pathway ◽  
Main Ring ◽  
Isotope Evidence

AbstractRecent studies indicate that the Rum Tertiary ultrabasic intrusion formed in situ, and was not emplaced as a fault-bounded plug. The suggestion that the Main Ring Fault was the primary pathway for the flow of meteoric-hydrothermal fluids on Rum is therefore seriously flawed. Oxygen isotope evidence is presented indicating that the contact zone of the intrusion was the major pathway for meteoric fluids during cooling of the pluton. δ18O depletions of over 12‰ correlate with hydrothermal alteration assemblages, indicating that the bulk of the interaction with meteoric fluids took place at low temperatures (200–450 °C).

Fuchsite and other Cr-rich phyllosilicates in ultramafic enclaves from the Almadén mercury mining district, Spain

Clay Minerals ◽  
2001 ◽  
Vol 36 (3) ◽  
pp. 345-354 ◽  
Author(s):  
D. Morata ◽  
P. Higueras ◽  
S. Domínguez-Bella ◽  
J. Parras ◽  
F. Velasco ◽  
...  
Keyword(s):  
High Temperature ◽  
Hydrothermal Alteration ◽  
Large Range ◽  
Block Size ◽  
Hydrothermal Fluids ◽  
Mining District ◽  
Cr Content ◽  
Mercury Mining ◽  
Early Alteration

AbstractFuchsite and other Cr-rich phyllosilicates, paragenetic with dolomite, are present in some ultramafic enclaves from the ‘frailesca’ rock (a lapilli- to block-size pyroclastic lithic-tuff), in the Almadén mercury mining district, Spain. Analyses (EMPA and TEM) of fuchsite and Cr-chlorite showed a relatively large range in levels of Cr2O3. Petrographic relationships between these phyllosilicates and primary relics of Cr-spinel crystals, as well as their high Cr content, indicate that these Cr-rich minerals originated from primary chromian spinels through an early hydrothermal alteration stage. The hydrothermal fluids accounting for this early alteration would be of relatively high temperature, high aCO2 and aK, and variable aNa/K. In a later alteration stage, fuchsite was partially or totally replaced by illite and Cr-illite, giving rise to an argillitic alteration.

scholarly journals Hydrothermal alteration of sediments in the high-temperature reaction zone at Central Hill of Escanaba Trough, Gorda Ridge

2019 ◽  
Vol 98 ◽  
pp. 08003
Author(s):  
Konstantin Galin ◽  
Alexandra Khakhina ◽  
Victor Kurnosov ◽  
Yurii Konovalov
Keyword(s):  
High Temperature ◽  
Hydrothermal Alteration ◽  
Hot Springs ◽  
Major Elements ◽  
Hydrothermal Fluids ◽  
Temperature Reaction ◽  
Rock Interaction ◽  
High Temperature Reaction ◽  
Gorda Ridge ◽  
Water Rock Interaction

In sediments from Holes ODP 1038A and 1038H, drilled near the hot springs at Central Hill, Escanaba Trough (Gorda Ridge), redistribution of major elements occurs during the water-rock interaction. Contents of Si, Fe, Mg, Ca, Na and K have changed in altered sediments. In this process, an increase/decrease in contents of major elements in altered sediments shows a decrease/increase in their contents in fluids. The irregular distribution of major elements in altered sediments resembles a layer pie, which reflects the existence of lateral flows of hydrothermal fluids.

Oxygen-isotope composition and temperature of fluids involved in deposition of Proterozoic sedex deposits, Sudbury Basin, Ontario

1990 ◽  
Vol 27 (10) ◽  
pp. 1299-1303 ◽  
Author(s):  
J. F. Davies ◽  
M. V. Leroux ◽  
R. E. Whitehead ◽  
Wayne D. Goodfellow
Keyword(s):  
Heat Source ◽  
Water Column ◽  
Oxygen Isotope ◽  
Hydrothermal Fluid ◽  
Isotope Composition ◽  
Oxygen Isotope Composition ◽  
Sea Floor

Sedex Cu–Pb–Zn deposits in the Sudbury Basin were deposited on the sea floor from fluids in which δ18O = −1‰ and at temperatures around 170 °C. Distal Mn-bearing sediments were deposited in seawater in which δ18O ≈ −3‰ and at temperatures around 125 °C. The fluids at the vent site (δ18O ≈ −1‰) probably represent a mixture of normal seawater and isotopically positive hydrothermal fluid generated in the substrate by seawater–rock reactions. The heat source responsible for convection and venting onto the sea floor and into the water column was the underlying Sudbury Irruptive, which was emplaced immediately following deposition of the Onaping Formation, directly above which the sedex deposits lie.

Variations in magnetic properties of Unit 10, Eastern Layered Intrusion, Isle of Rum, Scotland: implications for patterns of high temperature hydrothermal alteration

1995 ◽  
Vol 86 (2) ◽  
pp. 91-112 ◽  
Author(s):  
J. Housden ◽  
W. O'Reilly ◽  
S. J. Day
Keyword(s):  
Magnetic Properties ◽  
Fluid Flow ◽  
High Temperature ◽  
Hydrothermal Alteration ◽  
Hydrothermal Fluid ◽  
Layered Intrusion ◽  
Magnetic Data ◽  
Magnetic Studies ◽  
Alteration Minerals ◽  
High Concentrations

ABSTRACTAn in situ magnetic susceptibility survey of Unit 10 of the Eastern Layered Intrusion of the Isle of Rum, in a line perpendicular to the strike, was carried out as a guide to selecting sampling sites for subsequent laboratory magnetic studies. These laboratory studies indicate that the dominant magnetic phase is magnetite. An effective particle size of the magnetite was derived from the magnetic data: it was found that high concentrations (∼0·3%) of magnetite in the perioditites were achieved by the presence of fewer but larger particles. The regions of lower magnetite concentration (∼0·01%), which are mainly in the plagioclase-rich rocks, contain more abundant but smaller particles.The variations in magnetic properties correlate with the abundance and inferred temperatures of formation of hydrothermal alteration minerals in the rocks. Petrographic observations indicate temperatures of alteration of 500–800°C in the olivine-rich peridodites in the lower part of the Unit, but of the order of 300°C in the plagioclase-rich rocks at the top of the Unit.These relationships between magnetic mineralogy and hydrothermal alteration suggest that the magnetite was produced by olivine oxidation during hydrothermal alteration. It is proposed that variations in the magnetic properties of layered cumulate rocks may be used to map out variations in the temperature and intensity of hydrothermal fluid flow. The variations in the Unit 10 rocks studied are interpreted as indicating control of high-temperature hydrothermal fluid flow through them by contrast in permeability between brittle peridotites and quasiplastic plagioclase-rich rocks.

scholarly journals Triple oxygen isotope variations in magnetite from iron-oxide deposits, central Iran, record magmatic fluid interaction with evaporite and carbonate host rocks

Geology ◽  
2019 ◽  
Vol 48 (3) ◽  
pp. 211-215 ◽  
Author(s):  
Stefan T.M. Peters ◽  
Narges Alibabaie ◽  
Andreas Pack ◽  
Seann J. McKibbin ◽  
Davood Raeisi ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Oxygen Isotope ◽  
Carbonate Rocks ◽  
Isotope Composition ◽  
Central Iran ◽  
Magmatic Fluid ◽  
Isotope Data ◽  
O Isotopes ◽  
Magmatic Fluids ◽  
O Isotope

Abstract Oxygen isotope ratios in magnetite can be used to study the origin of iron-oxide ore deposits. In previous studies, only 18O/16O ratios of magnetite were determined. Here, we report triple O isotope data (17O/16O and 18O/16O ratios) of magnetite from the iron-oxide–apatite (IOA) deposits of the Yazd and Sirjan areas in central Iran. In contrast to previous interpretations of magnetite from similar deposits, the triple O isotope data show that only a few of the magnetite samples potentially record isotopic equilibrium with magma or with pristine magmatic water (H2O). Instead, the data can be explained if magnetite had exchanged O isotopes with fluids that had a mass-independently fractionated O isotope composition (i.e., MIF-O), and with fluids that had exchanged O isotopes with marine sedimentary carbonate rocks. The MIF-O signature of the fluids was likely obtained by isotope exchange with evaporite rocks of early Cambrian age that are associated with the IOA deposits in central Iran. In order to explain the triple O isotope composition of the magnetite samples in conjunction with available iron isotope data for magnetite from the deposits, we propose that magnetite formed from magmatic fluids that had interacted with evaporite and carbonate rocks at high temperatures and at variable water/rock ratios; e.g., magmatic fluids that had been released into the country rocks of a magma reservoir. Additionally, the magnetite could have formed from magmatic fluids that had exchanged O isotopes with SO2 and CO2 that, in turn, had been derived by the magmatic assimilation and/or metamorphic breakdown of evaporite and carbonate rocks.

scholarly journals Insights into the origin of carbonaceous chondrite organics from their triple oxygen isotope composition

2018 ◽  
Vol 115 (34) ◽  
pp. 8535-8540 ◽  
Author(s):  
Romain Tartèse ◽  
Marc Chaussidon ◽  
Andrey Gurenko ◽  
Frédéric Delarue ◽  
François Robert
Keyword(s):  
Organic Matter ◽  
Oxygen Isotope ◽  
Carbonaceous Chondrite ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Oxygen Isotope Composition ◽  
Insoluble Organic Matter ◽  
O Isotope ◽  
Protosolar Nebula ◽  
Mass Dependent

Dust grains of organic matter were the main reservoir of C and N in the forming Solar System and are thus considered to be an essential ingredient for the emergence of life. However, the physical environment and the chemical mechanisms at the origin of these organic grains are still highly debated. In this study, we report high-precision triple oxygen isotope composition for insoluble organic matter isolated from three emblematic carbonaceous chondrites, Orgueil, Murchison, and Cold Bokkeveld. These results suggest that the O isotope composition of carbonaceous chondrite insoluble organic matter falls on a slope 1 correlation line in the triple oxygen isotope diagram. The lack of detectable mass-dependent O isotopic fractionation, indicated by the slope 1 line, suggests that the bulk of carbonaceous chondrite organics did not form on asteroidal parent bodies during low-temperature hydrothermal events. On the other hand, these O isotope data, together with the H and N isotope characteristics of insoluble organic matter, may indicate that parent bodies of different carbonaceous chondrite types largely accreted organics formed locally in the protosolar nebula, possibly by photochemical dissociation of C-rich precursors.

Sign in / Sign up

Export Citation Format

Share Document