scholarly journals Reconstruction of an Early Permian, Sublacustrine Magmatic-Hydrothermal System: Mount Carlton Epithermal Au-Ag-Cu Deposit, Northeastern Australia

2020 ◽  
Vol 115 (1) ◽  
pp. 129-152
Author(s):  
Fredrik Sahlström ◽  
Zhaoshan Chang ◽  
Antonio Arribas ◽  
Paul Dirks ◽  
Craig A. Johnson ◽  
...  
Keyword(s):  
Hydrothermal System ◽  
Meteoric Water ◽  
Open Pit ◽  
Early Permian ◽  
High Sulfidation ◽  
Isotope Data ◽  
Epithermal Mineralization ◽  
Argillic Alteration ◽  
Advanced Argillic Alteration ◽  
Mineralizing Fluids

Abstract The Mt. Carlton Au-Ag-Cu deposit, northern Bowen basin, northeastern Australia, is an uncommon example of a sublacustrine hydrothermal system containing economic high-sulfidation epithermal mineralization. The deposit formed in the early Permian and comprises vein- and hydrothermal breccia-hosted Au-Cu mineralization within a massive rhyodacite porphyry (V2 open pit) and stratabound Ag-barite mineralization within volcano-lacustrine sedimentary rocks (A39 open pit). These orebodies are all associated with extensive advanced argillic alteration of the volcanic host rocks. Stable isotope data for disseminated alunite (δ34S = 6.3–29.2‰; δ18OSO4 = –0.1 to 9.8‰; δ18OOH = –15.3 to –3.4‰; δD = –102 to –79‰) and pyrite (δ34S = –8.8 to –2.7‰), and void-filling anhydrite (δ34S = 17.2–19.2‰; δ18OSO4 = 1.8–5.7‰), suggest that early advanced argillic alteration formed within a magmatic-hydrothermal system. The ascending magmatic vapor (δ34SΣS ≈ –1.3‰) was absorbed by meteoric water (~50–60% meteoric component), producing an acidic (pH ≈ 1) condensate that formed a silicic → quartz-alunite → quartz-dickite-kaolinite zoned alteration halo with increasing distance from feeder structures. The oxygen and hydrogen isotope compositions of alunite-forming fluids at Mt. Carlton are lighter than those documented at similar deposits elsewhere, probably due to the high paleolatitude (~S60°) of northeastern Australia in the early Permian. Veins of coarse-grained, banded plumose alunite (δ34S = 0.4– 7.0‰; δ18OSO4 = 2.3–6.0‰; δ18OOH = –10.3 to –2.9‰; δD = –106 to –93‰) formed within feeder structures during the final stages of advanced argillic alteration. Epithermal mineralization was deposited subsequently, initially as fracture- and fissure-filling, Au-Cu–rich assemblages within feeder structures at depth. As the mineralizing fluids discharged into lakes, they produced syngenetic Ag-barite ore. Isotope data for ore-related sulfides and sulfosalts (δ34S = –15.0 to –3.0‰) and barite (δ34S = 22.3–23.8‰; δ18OSO4 = –0.2 to 1.3‰), and microthermometric data for primary fluid inclusions in barite (Th = 116°– 233°C; 0.0–1.7 wt % NaCl), are consistent with metal deposition at temperatures of ~200 ± 40°C (for Au-Cu mineralization in V2 pit) and ~150 ± 30°C (Ag mineralization in A39 pit) from a low-salinity, sulfur- and metal-rich magmatic-hydrothermal liquid that mixed with vapor-heated meteoric water. The mineralizing fluids initially had a high-sulfidation state, producing enargite-dominated ore with associated silicification of the early-altered wall rock. With time, the fluids evolved to an intermediate-sulfidation state, depositing sphalerite- and tennantite-dominated ore mineral assemblages. Void-filling massive dickite (δ18O = –1.1 to 2.1‰; δD = –121 to –103‰) with pyrite was deposited from an increasingly diluted magmatic-hydrothermal liquid (≥70% meteoric component) exsolved from a progressively degassed magma. Gypsum (δ34S = 11.4–19.2‰; δ18OSO4 = 0.5–3.4‰) occurs in veins within postmineralization faults and fracture networks, likely derived from early anhydrite that was dissolved by circulating meteoric water during extensional deformation. This process may explain the apparent scarcity of hypogene anhydrite in lithocaps elsewhere. While the Mt. Carlton system is similar to those that form subaerial high-sulfidation epithermal deposits, it also shares several key characteristics with magmatic-hydrothermal systems that form base and precious metal mineralization in shallow-submarine volcanic arc and back-arc settings. The lacustrine paleosurface features documented at Mt. Carlton may be useful as exploration indicators for concealed epithermal mineralization in similar extensional terranes elsewhere.

The Onto Cu-Au Discovery, Eastern Sumbawa, Indonesia: A Large, Middle Pleistocene Lithocap-Hosted High-Sulfidation Covellite-Pyrite Porphyry Deposit

2020 ◽  
Vol 115 (7) ◽  
pp. 1385-1412
Author(s):  
David R. Burrows ◽  
Michael Rennison ◽  
David Burt ◽  
Rod Davies
Keyword(s):  
Sea Level ◽  
Shallow Depth ◽  
Middle Pleistocene ◽  
High Sulfidation ◽  
Copper Mineralization ◽  
Argillic Alteration ◽  
Zircon Crystallization ◽  
Current Resource ◽  
Advanced Argillic Alteration ◽  
Host Rocks

Abstract In 2013, a diamond drill program tested an extensive advanced argillic alteration lithocap within the Hu’u project on eastern Sumbawa Island, Indonesia. A very large and blind copper-gold deposit (Onto) was discovered, in which copper occurs largely as disseminated covellite with pyrite, and as pyrite-covellite veinlets in a tabular block measuring at least 1.5 × 1 km, with a vertical thickness of ≥1 km. Copper and gold are spatially related with a series of coalesced porphyry stocks that intrude a polymictic diatreme breccia capped by a sequence of intramaar laminated siltstones, volcaniclastic and pyroclastic rocks, and overlain by andesite flows and domes. The porphyry intrusions were emplaced at shallow depth (≤1.3 km), with A-B–type quartz veinlet stockworks developed over a vertical interval of 300 to 400 m between ~100 and 500 m below sea level (bsl), 600 to 1,000 m below the present surface, which is at 400 to 600 m above sea level. In the area drilled at Onto, the diatreme breccia, all porphyry intrusions and, to a lesser extent, the surrounding older andesite sequence have all been overprinted by intense subhorizontal advanced argillic alteration, zoned downward from illite-smectite, quartz-dickite to quartz-alunite and quartz-pyrophyllite ± diaspore alteration. The alteration package includes two particularly well-developed zones of residual quartz with vuggy texture in subhorizontal zones at shallow depth, the upper one is still porous but the lower horizon, ~100 m thick, is largely silicified and is located at or near the top of the quartz-alunite alteration. Mineralization starts below the lowermost silicic horizon with more than 90% of the current resource in quartz-pyrophyllite-alunite and quartz-alunite alteration. Mineralization is dominated by a high-sulfidation assemblage of covellite-pyrite ± native sulfur largely in open-space fillings and replacements, but also as discrete pyrite-covellite and covellite only veins down to at least 1 km. Although the greatest amount of copper occurs as paragenetically late covellite deposited during formation of the advanced argillic alteration, approximately 60% of resource at 0.3% Cu cutoff still occurs within the porphyry stocks, indicating the porphyry stocks are a fundamental control on mineralization. There is considerable remobilization and dispersion of copper and, to a lesser extent, gold into the surrounding pre-mineral breccia and the late intermineral intrusions from the two earliest porphyry phases, resulting in quite consistent copper and gold grades throughout the currently delineated mineral resource. The very high sulfidation state of the mineralization is thought to be a consequence of the metal-bearing ore fluids cooling in the advanced argillic-altered host rocks in the absence of a rock buffer. Early chalcopyrite-bornite ± pyrite mineralization with potassic ± chloritic and sericitic alteration is only preserved on the margins of the system and more rarely at depth in a few holes 600 m bsl (~1,100 m below surface) but makes up only a small proportion (~8%) of the current resource. The Onto system is exceptionally young and formed rapidly in the middle Pleistocene and is not significantly eroded. A U-Pb zircon age for the andesite that caps the volcanosedimentary host rocks provides a maximum age of 0.838 ± 0.039 Ma, with a slightly younger porphyry zircon crystallization age of 0.688 ± 0.053 Ma. Re-Os dating of molybdenite that is associated with both the quartz vein stockwork and high-sulfidation assemblage copper mineralization shows overlap between 0.44 ± 0.02 and 0.35 ± 0.0011 Ma. 40Ar/39Ar ages for alunite within the advanced argillic alteration block ranges from 0.98 ± 0.22 to 0.284 ± 0.080 Ma, and alunite closely associated with covellite spans a period from 0.537 ± 0.064 to 0.038 ± 0.018 Ma.

Aluminium phosphate mineralization from the hypogene La Vanguardia kaolin deposit (Chile)

Clay Minerals ◽  
1995 ◽  
Vol 30 (3) ◽  
pp. 249-256 ◽  
Author(s):  
H. G. Dill ◽  
A. Fricke ◽  
K.-H. Henning ◽  
C. H. Theune
Keyword(s):  
Optical Microscopy ◽  
Open Pit ◽  
Aluminium Phosphate ◽  
San Lorenzo ◽  
Argillic Alteration ◽  
Phosphate Mineralization ◽  
Advanced Argillic Alteration ◽  
Kaolin Deposit

AbstractIn the region of Illapel, Chile, dioritic and andesitic rocks of Cretaceous to Paleocene age from the Unidad San Lorenzo Formation have suffered strong alteration resulting in the formation of a kaolin-rich zone, which is mined in the La Vanguardia open pit near Combarbalá. Detailed mineralogical and chemical investigations of channel samples from this mine, involving a combination of optical microscopy, XRD, SEM-EDX, XRF and TEM, permitted recognition of a zone of silicification and a zone of advanced argillic alteration, both of which contain alunite s.s. and aluminium-phosphate-sulphate (APS) minerals of the woodhouseite group with subordinate amounts of gorceixite, florencite and goyazite. These minerals are found to have originated from infiltration of meteoric waters. The passage from silicification into advanced argillic alteration was associated with an increase in sulphate activity as manifested by the increase of SO42— at the expense of PO43— in the alunite s.s. and by an increase of the Au content from 0.01 to 0.03 mg/kg Au. This high sulphidation type of wallrock alteration may be roughly compared with the Nansatu type of White (1991).

Chapter 22: Gold Deposits of the Yanacocha District, Cajamarca, Peru

2020 ◽  
pp. 451-465
Author(s):  
Richard Pilco ◽  
Sean McCann
Keyword(s):  
Joint Venture ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Epithermal Gold ◽  
Sulfide Deposits ◽  
High Sulfidation ◽  
Significant Potential ◽  
Argillic Alteration ◽  
Northern Peru ◽  
Advanced Argillic Alteration

Abstract The Yanacocha district of northern Peru has produced >37 million ounces (Moz) Au since production commenced in 1993. Recognized as one of the world’s most prolific high-sulfidation epithermal gold districts, its discovery was made over a four-year period (1984–1988) through a joint venture alliance operated by Newmont Corporation. Over the past 30 years the geologic understanding of the district has been enhanced by research and documentation by many academic and Newmont geoscientists. The gold deposits are hosted within Tertiary volcanic rocks consisting of pyroclastic sequences cut by several generations of breccias and intrusions, all of which have undergone silicic and advanced argillic alteration. A dominant NE-trending structural corridor bounds all deposits in the district, and local northwest fault intersections with this trend are complimentary controls on mineralization. There are 12 major deposits discovered and exploited at Yanacocha. The largest, Cerro Yanacocha, has produced >17.5 Moz Au, whereas the newest deposit to be delineated, Antonio, has a >1.0 Moz resource. The depletion of shallow, supergene-oxidized deposits has necessitated the current underground development to exploit deeper sulfide deposits. Significant potential remains within the Yanacocha district in both oxide and sulfide deposits, and ongoing exploration efforts, are leveraging learnings from mined deposits and advances in exploration technologies and tools to extend the mine life.

scholarly journals Multistage alteration, mineralization and ore–forming fluid properties at the Viper (Sappes) Au–Cu–Ag–Te ore body, W. Thrace, Greece.

2016 ◽  
Vol 47 (4) ◽  
pp. 1635 ◽  
Author(s):  
S.P. Kilias ◽  
J. Naden ◽  
M. Paktsevanoglou ◽  
M. Giampouras ◽  
A. Stavropoulou ◽  
...  
Keyword(s):  
High Grade ◽  
Crystallization Sequence ◽  
High Sulfidation ◽  
Ore Body ◽  
Argillic Alteration ◽  
Vein Type ◽  
Fluid Properties ◽  
Water Fugacity ◽  
Advanced Argillic Alteration ◽  
Ph Increase

The mineralogy of ore and hydrothermal alteration of the high-sulfidation enargite–Au–Ag–Te Viper (Thrace) orebody, and fluid inclusions, were studied in drillcore samples. The hydrothermal system has evolved through several stages from pre-ore advanced argillic I+vuggy silica alteration, ore-stage advanced argillic II+vuggy silica alteration and silicification that has developed to argillic alteration (sericite)+silicification through pH increase, and a return to acid conditions as crosscutting post-ore advanced argillic alteration III+silicification. Ore is characterized by early barren pyrite I corroded by: (i) enargite–Au± complex Pb–Bi–Cu sulfosalts, tellurides and selenides, coexisting with euhedral quartz, and (ii) zoned pyrite II distinguished by anomalous concentrations of Au, Cu, As, Te, Bi, Pb, Se, within vuggy quartz. High-grade gold ore is also intergrown with late brecciacementing and vein-type epithermal-like banded quartz+ pyrite. These alteration and mineralization observations are consistent with the changing composition, water fugacity, and density of an expanding column of metal-laden magmatic vapor, combined with changes in structural permeability. Part of the enargite─Au─ quartz assemblages have been probably quenched from sulfosalt melt at high─temperatures (>575°C). End product of the enargite–sulfhide–silica crystallization sequence is the formation of high-grade epithermal quartz-gold colloformbanded ore during cooling and/or dilution/mixing down to ~200°C.

scholarly journals Mineralogical Study of the Advanced Argillic Alteration Zone at the Konos Hill Mo–Cu–Re–Au Porphyry Prospect, NE Greece

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 479 ◽  
Author(s):  
Constantinos Mavrogonatos ◽  
Panagiotis Voudouris ◽  
Paul G. Spry ◽  
Vasilios Melfos ◽  
Stephan Klemme ◽  
...  
Keyword(s):  
Deep Level ◽  
Stoichiometric Composition ◽  
Aluminum Phosphate ◽  
Alteration Zone ◽  
High Sulfidation ◽  
Argillic Alteration ◽  
Ore Minerals ◽  
Mineralogical Study ◽  
Wide Compositional Range ◽  
Advanced Argillic Alteration

The Konos Hill prospect in NE Greece represents a telescoped Mo–Cu–Re–Au porphyry occurrence overprinted by deep-level high-sulfidation mineralization. Porphyry-style mineralization is exposed in the deeper parts of the system and comprises quartz stockwork veins hosted in subvolcanic intrusions of granodioritic composition. Ore minerals include pyrite, molybdenite, chalcopyrite, and rheniite. In the upper part of the system, intense hydrothermal alteration resulted in the formation of a silicified zone and the development of various advanced argillic alteration assemblages, which are spatially related to N–S, NNW–SSE, and E–W trending faults. More distal and downwards, advanced argillic alteration gradually evolves into phyllic assemblages dominated by quartz and sericite. Zunyite, along with various amounts of quartz, alunite, aluminum phosphate–sulfate minerals (APS), diaspore, kaolinite, and minor pyrophyllite, are the main minerals in the advanced argillic alteration. Mineral-chemical analyses reveal significant variance in the SiO2, F, and Cl content of zunyite. Alunite supergroup minerals display a wide compositional range corresponding to members of the alunite, beudantite, and plumbogummite subgroups. Diaspore displays an almost stoichiometric composition. Mineralization in the lithocap consists of pyrite, enargite, tetrahedrite/tennantite, and colusite. Bulk ore analyses of mineralized samples show a relative enrichment in elements such as Se, Mo, and Bi, which supports a genetic link between the studied lithocap and the underlying Konos Hill porphyry-style mineralization. The occurrence of advanced argillic alteration assemblages along the N–S, NNW–SSE, and E–W trending faults suggests that highly acidic hydrothermal fluids were ascending into the lithocap environment. Zunyite, along with diaspore, pyrophyllite, and Sr- and Rare Earth Elements-bearing APS minerals, mark the proximity of the hypogene advanced argillic alteration zone to the porphyry environment.

scholarly journals MINERALOGY AND GEOCHEMISTRY OF THE TRIADESGALANA PB-ZN-AG-AU INTERMEDIATE-HIGH SULFIDATION EPITHERMAL MINERALIZATION, MILOS ISLAND, GREECE

2017 ◽  
Vol 50 (4) ◽  
pp. 1969
Author(s):  
K. Papavasiliou ◽  
P. Voudouris ◽  
C. Kanellopoulos ◽  
D. Alfieris ◽  
S. Xydous
Keyword(s):  
Hydrothermal System ◽  
Precious Metals ◽  
Common Source ◽  
Ore Formation ◽  
Pyroclastic Rocks ◽  
High Sulfidation ◽  
Dacitic Lava ◽  
Epithermal Mineralization ◽  
Lava Domes ◽  
Magmatic Gases

The Triades-Galana Pb-Zn-Ag-Au mineralization is a shallow-submarine epithermal mineralization located along NE-trending faults, NW Milos Island, Greece. It is hosted in 2.5–1.4 Ma pyroclastic rocks and is genetically related to andesitic/dacitic lava domes. Mineralization occurs as breccias, quartz-barite galena veins and stockworks within sericite-adularia or kaolinitic altered rocks. The mineralization is enriched in Mo, W and base- and precious metals (e.g. Pb, Zn, Ag) similarly to the neighbouring mineralization at Kondaros-Katsimouti and Vani, indicating common source of metals from a deep buried granitoid feeding western Milos with metals and volatiles. Paragenetic relations suggest early deposition of pyrite, followed by famatinite, polybasite and Ag-rich tetrahedrite, and then by enargite, suggesting fluctuating sulfidation states during ore formation. The evolution from Sb- towards As-rich enrichment indicate a renewed magmatic pulse (probably in the form of magmatic gases) in the hydrothermal system. Silver is present in the structure of sulfosalts (up to 66.2 wt.% in polybasite-pearceite, 15.1 wt.% in tetrahedrite and 60 wt. % in pyrargyrite). Boiling processes (as evidenced by the presence of adularia accompanying intermediate-sulfidation ore) and mixing with seawater (presence of hypogene lead chlorides) and contemporaneous uplift, contributed to ore formation.

scholarly journals Exploring magmatic gas and subvolcanic hydrothermal system interactions: Mineralogy and sulfur isotope characteristics of the Holocene volcanic products at Mt. Tangkuban Parahu, Indonesia.

2021 ◽  
Author(s):  
Syahreza Saidina Angkasa ◽  
Ohba Tsukasa ◽  
Imura Takumi ◽  
Pearlyn Manalo ◽  
Takahashi Ryohei
Keyword(s):  
Hydrothermal System ◽  
Sulfur Isotope ◽  
Isotope Analysis ◽  
Volcanic Edifice ◽  
Acid Sulfate ◽  
The Holocene ◽  
Argillic Alteration ◽  
Magmatic Fluids ◽  
Mineral Assemblages ◽  
Advanced Argillic Alteration

Abstract A subvolcanic-hydrothermal system involves complex interaction between magma, magmatic fluids, and hydrothermal system at stratovolcanoes in subduction setting. These interactions are responsible for magmatic-hydrothermal eruption associated with rapid injection of magmatic gas into hydrothermal system at a certain depth of volcanic edifice. However, capturing these interactions is challenging due to inaccessibility to the crater conduit within the edifice. Therefore, we selected a method to analyze the volcanic products from several episodic phreatic and phreatomagmatic eruptions during the Holocene at Tangkuban Parahu, Indonesia. In this context, Holocene volcanic products are one of the best examples to understand an interplay between magma, magmatic fluids, and hydrothermal system in producing violent eruptions. In this study, we carried out petrological and sulfur isotope analysis only for the hydrothermally altered lithic ash particles, a part of proximal volcanic products. Mineral assemblages mostly exhibit a typical acid-sulfate and advanced argillic alteration, consisting of alunite, kaolinite, and silica minerals. Acid-sulfate and advanced argillic alteration indicates that those mineral assemblages were formed under the formation temperature ranging from ~100 to ~260 . The calculated temperature from sulfur isotopic fractionation of sulfate-sulfide shows 230-240 , which is almost identical with assigned temperature from mineral assemblages. Sulfur isotope and jarosite occurrence indicate the supergene alteration associated with oxygen entrainment to the hydrothermal system that oxidize pyrite to jarosite. Sulfur isotopic variation throughout the studied stratigraphy represents influx of magmatic gas to the hydrothermal system. Moreover, zoned P-bearing alunite represents repetitive injection of magmatic gas to the active acidic hydrothermal system, which also indicates the magmatic-hydrothermal interaction below the crater. Occurrence of enargite and chalcopyrite represents the nature of upper-level high sulfidation system at shallow volcanic edifice of the Tangkuban Parahu volcano. Furthermore, we showed that coupled petrological and sulfur isotope analysis has paramount importance to evaluate the conditions of the subvolcanic hydrothermal system, magmatic-hydrothermal interaction, and the origin of steam-blast eruptions at volcanoes that contain subvolcanic-hydrothermal systems.

Paragenesis of veins of the Duck Pond tin prospect, Meguma Group, East Kemptville, Nova Scotia

1989 ◽  
Vol 26 (10) ◽  
pp. 2032-2043 ◽  
Author(s):  
Christian V. Pitre ◽  
Jean M. Richardson
Keyword(s):  
Nova Scotia ◽  
Manganese Oxides ◽  
Open Pit ◽  
Granitic Magma ◽  
Sulphide Minerals ◽  
Main Indicator ◽  
Argillic Alteration ◽  
Mineral Assemblages ◽  
Indicator Mineral ◽  
Host Rocks

The Duck Pond tin prospect is a vein- and strata-bound cassiterite prospect that is located 2 km west of the East Kemptville open-pit tin mine in southwestern Nova Scotia. The host rocks of the Duck Pond prospect are interbedded metawacke and meta-argillite that belong to the transition unit of the Meguma Group. These rocks contain quartz, sericite, chlorite, hematite, rutile, manganese oxides, feldspar, and porphyroblastic garnet, but not detrital cassiterite. The prospect is structurally controlled and contains several cross-cutting vein sets that have alkalic, chloritic, or argillic alteration assemblages. Muscovite is the main indicator mineral for alkalic alteration and occurs in veins that contain anorthoclase or quartz. Cassiterite is associated with chloritic alteration and occurs as subhedral to euhedral grains, acicular needles, and colloform layers in veins in meta-argillite and as strata-bound disseminations in metawacke. Most cassiterite precipitated under externally buffered conditions with respect to oxygen. Fe, Cu, Zn, and As sulphide minerals and quartz were deposited during argillic alteration. Late-stage processes such as recrystallization, sulphidation, and oxidation also occurred. Chalcopyrite is replaced by bornite and covellite; pyrite is replaced by marcasite.Unlike the F-rich East Kemptville deposit, fluorine-rich and tin-sulphide minerals are not present in the Duck Pond prospect. Trace tourmaline, absent at East Kemptville, is found at Duck Pond. However, the source of tin-mineralizing fluids at Duck Pond and East Kemptville was likely the granitic magma of the Davis Lake complex, which also hosts the East Kemptville deposit. From the mineral assemblages and textural relationships, it appears that as the temperature dropped from 425–405 °C to less than 200 °C at Duck Pond, the pH dropped from 5.2 to no lower than 3. Log [Formula: see text] dropped from at least −19 to −43. Log [Formula: see text] rose from < −15 to > −10. Cassiterite precipitated at the higher ends of the temperature and pH ranges and the lower end of the log [Formula: see text] range.

scholarly journals Comment on “Origin of water in the Badain Jaran Desert, China: new insight from isotopes” by Wu et al. (2017)

2018 ◽  
Vol 22 (8) ◽  
pp. 4449-4454 ◽  
Author(s):  
Lucheng Zhan ◽  
Jiansheng Chen ◽  
Ling Li ◽  
David A. Barry
Keyword(s):  
Lake Water ◽  
Meteoric Water ◽  
Isotope Composition ◽  
Qilian Mountains ◽  
Precipitation Rate ◽  
Badain Jaran Desert ◽  
Isotopic Evidence ◽  
Isotope Data ◽  
Local Areas ◽  
The Qilian Mountains

Abstract. Precipitation isotope data were used to determine the origin of groundwater in the Badain Jaran Desert (BJD) in the study of Wu et al. (2017). Both precipitation and its isotope composition vary seasonally, so arithmetic averages of precipitation isotope values poorly represent the isotope composition of meteoric water. Their finding that the BJD groundwater is recharged by modern meteoric water from local areas including the southeastern adjacent mountains was based on arithmetic averaging. However, this conclusion is not supported by the corrected mean precipitation isotope values, which are weighted by the precipitation rate. Indeed, the available isotopic evidence shows that modern precipitation on the Qilian Mountains is more likely to be the main source of the groundwater and lake water in the BJD, as found by Chen et al. (2004).

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