The role of disseminated calcite in the chemical weathering of granitoid rocks

White, Art F.; Bullen, Thomas D.; Vivit, Davison V.; Schulz, Marjorie S.; Clow, David W.

doi:10.1016/s0016-7037(99)00082-4

Cited by 255 publications

(156 citation statements)

References 38 publications

Supporting

Mentioning

145

Contrasting

Unclassified

Order By: Relevance

“…The maximum Ca contribution from carbonates is ϳ29% for the rivers used in calculation This is unlike granites/ gneiss watersheds, where Ca supply from such minor phases are reported to be more significant (Blum et al, 1998;White et al, 1999;Oliva et al, 2004). This difference is attributable to high Ca in basalts, relative ease of their weathering, and their relatively low carbonate content.…”

Section: Role Of Carbonates In Ca Budgetmentioning

confidence: 92%

“…It has been shown in some of the earlier studies on granite watersheds (Blum et al, 1998;White et al, 1999;Jacobson et al, 2002;Oliva et al, 2004) that Ca-rich minor phases such as calcite, apatites, and Ca-rich silicates present in these rocks can be a major source of Ca to rivers draining them. The role of such phases in contributing to Ca budget of Deccan rivers is evaluated below.…”

Section: Role Of Carbonates In Ca Budgetmentioning

confidence: 99%

See 1 more Smart Citation

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

Das

Krishnaswami

Sarin

et al. 2005

Geochimica et Cosmochimica Acta

175

142

View full text Add to dashboard Cite

Section: Role Of Carbonates In Ca Budgetmentioning

confidence: 92%

Section: Role Of Carbonates In Ca Budgetmentioning

confidence: 99%

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

Das

Krishnaswami

Sarin

et al. 2005

Geochimica et Cosmochimica Acta

175

142

View full text Add to dashboard Cite

“…2) indicate that most of the solutes in the investigated groundwater are derived from silicate weathering, which consumes protons, contributes cations, and converts soil gas CO 2 to bicarbonate (Drever, 1997). Bicarbonate may also be derived from organic carbon oxidation or calcite dissolution, although the latter should be insignificant in longexposed granites in areas where denudation rates are low, such as the southeastern United States (White et al, 1999). The mass balance of dissolved oxygen (up to~0.3 mM at atmospheric saturation, ranging to near zero in some samples) suggests that a large proportion of bicarbonate (median 0.98 mM for all samples, 0.57 mM in the Rolesville Granite) is derived from the open system of unsaturated zone CO 2 rather than organic carbon oxidation in the saturated zone.…”

Section: Major Element and Redox Chemistry Of Potential Ra Sinksmentioning

confidence: 99%

Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

et al. 2009

View full text Add to dashboard Cite

a b s t r a c t a r t i c l e i n f oNaturally-occurring radionuclides (uranium, radium, and radon), major dissolved constituents, and trace elements were investigated in fresh groundwater in 117 wells in fractured crystalline rocks from the Piedmont region (North Carolina, USA). Chemical variations show a general transition between two water types: (1) slightly acidic (pH 5.0-6.0), oxic, low-total dissolved solids (TDS) waters, and (2) near neutral, oxic to anoxic, higher-TDS waters. The uranium, radium, and radon levels in groundwater associated with granite (Rolesville Granite) are systematically higher than other rock types (gneiss, metasedimentary, and metavolcanic rocks). Water chemistry plays a secondary role on radium and radon distributions as the 222 Rn/ 226 Ra activity ratio is correlated with redox-sensitive solutes such as dissolved oxygen and Mn concentrations, as well as overall dissolved solids content including major divalent cations and Ba. Since 224 Ra/ 228 Ra activity ratios in groundwater are close to 1, we suggest that mobilization of Ra and Rn is controlled by alpha recoil processes from parent nuclides on fracture surfaces, ruling out Ra sources from mineral dissolution or significant long-distance Ra transport. Alpha recoil is balanced by Ra adsorption that is influenced by redox conditions and/or ion concentrations, resulting in an approximately one order of magnitude decrease (~20,000 to~2000) in the apparent Ra distribution coefficient between oxygensaturated and anoxic conditions and also across the range of dissolved ion concentrations (up to~7 mM). Thus, the U and Th content of rocks is the primary control on observed Ra and Rn activities in groundwater in fractured crystalline rocks, and in addition, linked dissolved solids concentrations and redox conditions impart a secondary control.

show abstract

“…For example, log rates from laboratory experiments are −6 to −10 for pyrite (20), vs. log rates of −10 to −16 for silicate minerals (21). Thus, even a small proportion of sulfide or carbonate present in rocks can dominate solute production (22,23). Indeed, weathering of these trace phases is predominantly "supply limited" in the present day, so fluxes increase with erosion that supplies more minerals for reaction (17,24).…”

mentioning

confidence: 99%

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Torres

Moosdorf

Hartmann

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

141

171

View full text Add to dashboard Cite

Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO 2 , we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO 2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO 2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO 2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O 2 . Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.weathering | carbon cycle | glaciation | oxidation | sulfide E pisodes of glaciation represent some of the most dramatic changes in the history of Earth's climate. Basic questions remain unanswered about why the planet has occasionally but not always supported glaciers, about why some glaciations have been more intense than others, and about how glaciers have shaped Earth's landscapes, chemical cycles, and climate. Before the Phanerozoic (i.e., before ∼540 Mya), several glaciations are thought to have approached complete or near-complete planetary ice cover ("Snowball Earth" events; ref. 1). In contrast, more recent glaciations, including the Quaternary glaciations of the last million years, have been characterized by oscillating climate with ice extent limited to high latitudes even during glacial maxima (2). The formation of ice cover has long been known to fundamentally alter Earth's environment, changing albedo (3), influencing atmospheric and ocean circulation (4), and reshaping landscapes (5). These diverse effects may contribute to planetary-scale feedbacks that influence the transition to and the evolution of glaciation.Chemical weathering influences the composition of the atmosphere by releasing ionic species from minerals that alter the alkalinity and redox condition of the ocean-atmosphere system. Weathering of silicate minerals produces alkalinity, removing carbon from the at...

show abstract

The role of disseminated calcite in the chemical weathering of granitoid rocks

Cited by 255 publications

References 38 publications

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

Chemical weathering in the Krishna Basin and Western Ghats of the Deccan Traps, India: Rates of basalt weathering and their controls

Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

Contact Info

Product

Resources

About