scispace - formally typeset
Search or ask a question
Topic

Silicate minerals

About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.


Papers
More filters
Journal ArticleDOI
01 Jun 2005-Geology
TL;DR: A suite of needle-shaped titanomagnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions' magnetic domain state as discussed by the authors.
Abstract: Submicroscopic, needle-shaped titanomagnetite inclusions exsolved in silicate minerals commonly occur in mafic intrusive rocks and are protected from alteration by their silicate hosts, making them excellent candidates for paleomagnetic studies. A suite of samples containing clinopyroxene- and plagioclase-hosted magnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions' magnetic domain state. Alternating field demagnetization experiments indicate that some inclusions are more stable recorders than others. The two factors controlling the remanence behavior of the inclusions are internal microstructures and inclusion dimensions. Magnetite-ulvospinel unmixing within an inclusion subdivides the original titanomagnetite solid solution into a boxwork structure composed of 103–105 magnetite prisms separated by thin ulvospinel lamellae. The conversion of multidomain-sized needles into assemblages of interacting single domains increases the coercivity (and hence relaxation time) of the inclusions, and results in a thermochemical magnetic remanence. In samples without this exsolution microstructure, the inclusions' diameters determine coercivity and their magnetization is thermoremanent. Both styles of high-coercivity inclusions successfully record paleomagnetic directions in Mesozoic rocks, and their ubiquity within silicate minerals (clinopyroxene and plagioclase) of mafic intrusive rocks indicates their value as chemically and magnetically stable tools for elucidating the ancient magnetic field, marine magnetic anomalies, and crustal kinematics.

128 citations

Journal ArticleDOI
01 Oct 2012-Geology
TL;DR: In this paper, an in situ atomic force microscopy (AFM) study of the dissolution of wollastonite, CaSiO 3, as an example of surface leached layer formation during dissolution is presented.
Abstract: The dissolution of most common multicomponent silicate minerals and glasses is typically incongruent, as shown by the nonstoichiometric release of the solid phase components. This results in the formation of so-called surface leached layers. Due to the important effects these leached layers may have on mineral dissolution rates and secondary mineral formation, they have attracted a great deal of research. However, the mechanism of leached layer formation is a matter of vigorous debate. Here we report on an in situ atomic force microscopy (AFM) study of the dissolution of wollastonite, CaSiO 3 , as an example of leached layer formation during dissolution. Our in situ AFM results provide, for the first time, clear direct experimental evidence that leached layers are formed in a tight interface-coupled two-step process: stoichiometric dissolution of the pristine mineral surfaces and subsequent precipitation of a secondary phase (most likely amorphous silica) from a supersaturated boundary layer of fluid in contact with the mineral surface. This occurs despite the fact that the bulk solution is undersaturated with respect to the secondary phase. Our results differ significantly from the concept of preferential leaching of cations, as postulated by most currently accepted incongruent dissolution models. This interface-coupled dissolution-precipitation model has important implications in understanding and evaluating dissolution kinetics of major rock-forming minerals.

127 citations

Book ChapterDOI
01 Jan 2014
Abstract: Rare elements include rare-earth elements (REE), Nb, Ta, Zr, and Hf. As a group, these elements are concentrated in the crust and are incompatible (remain in the melt rather than substitute into silicate minerals). Carbonatites host the most important deposits of REE and Nb, although peralkaline granites and silica under saturated rocks also host deposits of these elements. By contrast, Ta is concentrated in peraluminous granites and pegmatites. The former types of deposits are characterized by rift and anorogenic tectonic settings, whereas the latter, most typically, are in collisional settings. Rare elements are concentrated by magmatic processes; in silicate melts one of the most important controls on rare element mineral solubility is the (Na + K)/Al ratio of the melt. Their solubilities are also temperature dependent and both these parameters may control magmatic ore deposition. Fluid–melt partition coefficients are typically low, but nonetheless the grades in many rare-element deposits are highest where hydrothermal alteration is strongly developed. Rare elements are hard acids in the Pearson sense and they prefer to bond electrostatically to form aqueous complexes with hard bases such as F − and OH − , as well as SO 4 2 − , CO 3 2 − , and PO 4 3 − . Fluid mixing may be the principal control of mineralization in hydrothermal systems.

126 citations

Journal ArticleDOI
01 May 2000-Geology
TL;DR: In this paper, a trace amount of disseminated calcite was identified in gneiss, schist, and granite bedrock sampled from the Raikhot watershed and other locations within the Nanga Parbat massif of northern Pakistan.
Abstract: Trace amounts of disseminated calcite were identified in gneiss, schist, and granite bedrock sampled from the Raikhot watershed and other locations within the Nanga Parbat massif of northern Pakistan. The calcite grains occur interstitially within individual silicate minerals, at grain boundaries, and as fracture fillings that transect the mineralogic fabric of the rock. Disseminated calcite composes is ≤ 0.29 wt% of silicate rocks sampled in the Raikhot watershed and has Ca/Sr (µmol/nmol) and 87Sr/86Sr ratios that range from 0.878 to 5.33 and from 0.794 039 to 0.930 619, respectively. Elsewhere in the Nanga Parbat region, disseminated calcite composes ≤ 3.6 wt% of the silicate rock samples and has Ca/Sr (µmol/nmol) and 87Sr/86Sr ratios that range from 0.535 to 3.33 and from 0.715 757 to 0.771 244, respectively. For all samples, the 87Sr/86Sr ratios of disseminated calcite are similar to the 87Sr/86Sr ratios measured in the silicate host rock. Within the partially glaciated Raikhot watershed, the rapid weathering of disseminated calcite with high Ca/Sr and 87Sr/86Sr ratios has a strong influence on the chemical composition of stream water and exceeds contributions from silicate mineral dissolution. Comparisons of disseminated calcite compositions with source-water chemistry throughout the Himalaya suggest that disseminated calcite may be a more important component of Himalayan silicate rocks than previously recognized. Therefore, calculations relating the Sr isotope geochemistry of Himalayan rivers to atmospheric CO2 consumption should consider this widespread and compositionally variable carbonate end member.

125 citations

Journal ArticleDOI
05 Jun 1998-Science
TL;DR: In this paper, carbonate isotope measurements of carbonate from martian meteorite ALH 84001 (δ18O = 18.3 ± 0.4 per mil, δ17O = 10.3± 0.2 per millimeter, and Δ 17O = 0.8 ± 1.05 per mm) were used to support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars during carbonate growth.
Abstract: Oxygen isotope measurements of carbonate from martian meteorite ALH 84001 (δ18O = 18.3 ± 0.4 per mil, δ17O = 10.3 ± 0.2 per mil, and Δ17O = 0.8 ± 0.05 per mil) are fractionated with respect to those of silicate minerals. These measurements support the existence of two oxygen isotope reservoirs (the atmosphere and the silicate planet) on Mars at the time of carbonate growth. The cause of the atmospheric oxygen isotope anomaly may be exchange between CO2 and O(1D) produced by the photodecomposition of ozone. Atmospheric oxygen isotope compositions may be transferred to carbonate minerals by CO2-H2O exchange and mineral growth. A sink of17O-depleted oxygen, as required by mass balance, may exist in the planetary regolith.

125 citations


Network Information
Related Topics (5)
Carbonate
34.8K papers, 802.6K citations
83% related
Zircon
23.7K papers, 786.6K citations
83% related
Basalt
18.6K papers, 805.1K citations
83% related
Metamorphism
18.3K papers, 655.8K citations
82% related
Volcanic rock
19.5K papers, 610.1K citations
80% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
202264
202153
202064
201951
201865