Hydrochemical appraisal of ice- and rock-glacier meltwater in the hyperarid Agua Negra drainage basin, Andes of Argentina

LECOMTE, K. L., MILANA, J. P., FORMICA, S. AND DEPETRIS, P.

HYDROLOGICAL PROCESSES

JOHN WILEY & SONS LTD

Lugar: N.York; Año: 2007 vol. 22 p. 2180 - 2225

0885-6087

The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts. The Agua Negra drainage system (30º 12’S, 69º 50’ W), in the Argentine Andes holds several ice- and rock-glaciers, which are distributed from 4,200 up to 6,300 m a.s.l. The geochemical study of meltwaters reveals that ice-glaciers deliver a HCO3- - Ca2+ solution and rock-glaciers a SO42- - HCO3- - Ca2+ solution. The site is presumably strongly influenced by sublimation and dry deposition. The main processes supplying solutes to meltwater are sulfide oxidation (i.e., abundant hydrothermal manifestations), and hydrolysis and dissolution of carbonates and silicates. Marine aerosols are the main source for NaCl. The fine-grained products of glacial comminution play a significant role in the control of dissolved minor and trace elements: transition metals (e.g., Mn, Zr, Cu, and Co) appear to be selectively removed from solution, whereas some LIL (large ion lithophile) elements, such as Sr, Cs, and major cations, are more concentrated in the lowermost reach. Daily concentration variation of dissolved REE tends to increase with discharge. As in other mountainous streams, the extended UCC-normalized diagrams show a predominance of middle REE (Sm to Dy) over light and heavy REE. Through PHREEQC inverse modeling, gypsum dissolution is the most important geochemical mechanism delivering solutes to the Agua Negra drainage, particularly in rock-glaciers. At the lowermost reach, the chemical signature appears to change depending on the relative significance of different meltwater sources: silicate weathering seems to be more important when meltwater has a longer residence time, and calcite and gypsum dissolution is more conspicuous in recently melted waters. A comparison with a non-glacierized semiarid drainage of comparable size shows that the glacierized basin has a higher specific denudation, but it is mostly accounted for by relatively soluble phases (i.e., gypsum and calcite). Meltwater chemistry in glacierized arid areas seems strongly influenced by sublimation/evaporation, in contrast with its humid counterparts.