Quartz Debris Research Articles

Provenance of quartz debris in the Central Western Carpathians at the end of the Triassic, as indicated by cathodoluminescence colours

Lithic fragments including quartz grains occur infrequently in the shallow-marine limestone sequence of the Fatra Formation deposited in the tensional intra-shelf depression of the Central Western Carpathians during the Rhaetian. Nevertheless, their study can bring data answering questions of sources, palaeogeodynamic arrangement, and processes at the end of the Triassic. In this study, we examined optically the cathodoluminescence (CL) colours of single quartz grains from the Kardolína section (Tatra Mts, Slovakia). These colours reveal a dominance of grains derived from regionally metamorphosed and plutonic rocks. Grains of hydrothermal and pegmatite origin are less frequent. Some of the quartz grains show recycled cement rims suggesting at least a second cycle origin. This sedimentary basin was situated near to the passive margin formed by the Variscan consolidated terrains of the Vindelician Highlands. Our study of the CL colours of quartz grains contributes to the elucidation of the nature of the rocks of the vanished Vindelician mountain belt.

Effects of sandstone mineral composition heterogeneity on crack initiation and propagation through a microscopic analysis technique

Crack initiation and propagation are key scientific questions influencing rock failure. To study crack initiation and propagation during rock failure, CT scanning tests were performed on the sandstone samples. The initiation and propagation stages of sandstone cracks were analysed based on a reconstructed three-dimensional crack structure model. The types of crack initiation and propagation in minerals and the effects of mineral composition heterogeneity on crack initiation and propagation were studied using microscopic analytical techniques. The effect of mineral granularity on crack initiation and propagation was analysed using statistical methods. The results show that crack initiation and propagation can be divided into four stages: microcrack inoculation, mesocrack initiation, mesocrack evolution to macrocrack, and macrocrack penetration. Four cracks are formed at different locations, extending along the mineral edge, deflecting at the mineral edge, bifurcating at the mineral edge, and penetrating through the mineral. The poikilitic texture formed by quartz debris and cement makes it easy for cracks to extend along the mineral edges. In quartz debris with high crystallinity, the crack tends to deflect and bifurcate at the edge of quartz debris. The symbiotic structure of altered quartz and clay minerals easily causes cracks to propagate through the minerals. Furthermore, the distribution of mineral granularity affects crack initiation and propagation. The inhomogeneity of mineral granularity can easily cause the initiation and propagation of cracks. The size of the mineral granularity affects the width of the secondary crack. These research results can provide a basis and reference for predicting and evaluating the stability of rock masses.

Sunspot cycles recorded in Eocene lacustrine fine-grained sedimentary rocks in the Bohai Bay Basin, eastern China

Millennial-to-interannual events play important roles in driving climate change on Earth. However, most studies focus on Quaternary records, and few focus on pre-Quaternary periods due to preservation condition and stratigraphic resolution limitations. Favorable conditions for the preservation of annual laminae are recorded during the Eocene in the Shahejie Formation in the Bohai Bay Basin (BBB), which is an ideal place for studying solar activity cycles. Here, the sedimentary petrology and cyclostratigraphy of 202-m-thick lacustrine fine-grained sedimentary rocks during the Eocene from Well Niuye-1 were analyzed. Power spectrum analysis and evolutive harmonic analysis (EHA) of the gray values reveal prominent periodicities of 11.7–19.6 mm, 3.7–4.95 mm and 1.69–2.21 mm, interpreted as Gleissberg cycles, solar Hale cycles and Schwabe sunspot cycles, respectively. Laminar couplets of light and dark laminae have an average thickness of 189 μm, and their annual origin has been interpreted on meter, centimeter and millimeter scales. The light laminae, composed of pure calcite, likely precipitated during summer. The dark laminae, which are mixtures of clay minerals, quartz debris and organic matter, likely precipitated during winter. The dark laminae are thin, contributing little to the overall thicknesses of the annual laminae except for the abruptly thicker laminae deposited every 10–11 years. The coherent periods at different scales match the solar activity cycles well. The obvious solar activity cycles during the Eocene of the Shahejie Formation in the BBB suggest that solar activity did not significantly change during the transitional period from a greenhouse to an icehouse climate. • Lacustrine shale from the Eocene in the Bohai Bay Basin show clear annual sedimentary records. • The light laminae maybe precipitate in summer, while the dark laminae were likely precipitated in winter. • The laminar groups with an average thickness of 2.15 mm show clear 11-year sunspot cycles. • Analyzing varves is an effective method to identify sunspot cycles in ancient sediments.

Disentangling activity traces on Australian goldfields: An experimental study of quartz assemblages derived from knapping and gold prospecting

Archaeologists have long grappled with identifying quartz artefacts in the archaeological record. The particular fracture mechanics of quartz can complicate the distinction between knapped quartz, other types of deliberately broken quartz, and natural occurrences of this mineral. In Australia, the quartz ‘problem’ is compounded on goldfields, where quartz debris from knapping, gold mining and other processes has the potential to co-occur. This paper investigates whether quartz assemblages produced by Aboriginal knappers and post-contact gold prospectors each possess a unique ‘signature’. It compares two quartz assemblages made experimentally using different but commonly used techniques with potential for creating artefacts with similar features: knapping with a hammerstone, and gold prospecting with a pick-axe. The results indicate that most artefacts in each assemblage are amorphous and lack diagnostic markers. Nonetheless, differences between the products of each technique are apparent at the assemblage level. Overall, the results highlight the complexities involved in investigating and classifying quartz artefacts, including on goldfields, and emphasise the importance of a holistic, assemblage-based approach to the study of quartz artefacts from different time periods and manufacturing origins.

Evaluation of particle size reduction and agglomeration in dry grinding of natural quartz in a planetary ball mill

This study investigates particle size reduction and interparticle agglomeration in clear and milky quartz ground in a planetary ball mill for up to 32 h. Particle size distribution and specific surface area were assessed using laser scattering and nitrogen physisorption methods. The heterogeneity in size distribution was calculated using the Rosin-Rammler equation. The onset of agglomeration occurred earlier for clear quartz (4 h) than for milky quartz (16 h). The resistance of the agglomerates formed with clear quartz debris against alkaline dissolution was stronger. These differences were discussed considering the population of ultrafine particles, the line broadening of X-ray diffraction patterns and the paramagnetic centers measured by EPR spectroscopy. The increase in peroxy center concentration occurred simultaneously with the onset of agglomeration. Since no difference was found in hardness and fracture toughness, the lower grinding rates of milky quartz was explained by the higher fracture strength of its polycrystalline microtexture.

Tectonic control on the sedimentary architecture of Early Mesozoic mixed siliciclastic-carbonate Pseudoverrucano successions (southern Tuscany, Italy)

The mixed siliciclastic-carbonate successions of Early Mesozoic age exposed in the Pseudoverrucano tectonic units, along the coast of southern Tuscany (Montebrandoli and Punta delle Rocchette, Early Liassic) and in the Monti dell’Uccellina (Porticciolo di Cala di Forno and Salto del Cervo, Late Triassic) are characterized by fossil assemblages suggesting a close relationship with the coeval, mainly carbonate successions of the “Tuscan Series” while the depositional features are completely different. The composition of the mixed facies are similar, characterized by: i) recurring fining-upward sequences with well rounded but poorly selected white quartz-conglomerates, ii) coarse quartz sand grading to lagoonal lime-muds, or iii) thin intercalations or isolated quartz pebbles enclosed together with shell debris, within open marine although shallow carbonates. The depositional environments correspond to alluvial-fan complexes on narrow coastal plains merging with sandy beaches and lagoonal to shallow marine settings where the carbonate micritic deposition prevailed. This sedimentary style suggests that unsorted quartz debris was transported from an adjacent uplifted source area by gravity currents through very narrow coastal plains, and flowing into coastal lagoons or directly into the open sea, mixed coarse, land derived debris with open marine carbonate muds. The peculiar vertical evolution of the Pseudoverrucano facies suggests that the episodic input of siliciclastic materials was connected with storm events most probably triggered by tectonic pulses since no evidences of eustatic or climatic constrain on the sedimentation is apparent. The depositional features and fossil content of the mixed silicicla - stic-carbonate Pseudoverrucano successions argues for a coastal sedimentation on narrow shelves delimited by active, fault-bounded highs, representing the landward extension of the epicontinental/ pericontinental pelagic basins that from late Triassic in a regime of continental rifting, developed on the east-facing shelf of central Pangea.

Fluid inclusions in reservoirs of Weixinan Sag, Beibuwan Basin

Abstract To make sure the petroleum migrating direction and pool-forming model in the Weixinan sag, 4 wells were chosen to do research on fluid inclusions and petrography. The petroleum inclusions have three types: type I occurs in early cracks of quartz debris grains or the overgrowths inside, type II in the margins or overgrowths of quartz grains, and type III in late cracks of quartz debris grains. According to PVTsim, Ptr and Ttr are modeled and calculated. The results are: type I is 97.9 °C and 19.13 MPa; type II 112.6 °C and 35.05 MPa; type III 157.4 °C and 47.52 MPa. Based on burial history, three fluid-charging events occurred about 33Ma, 26.5Ma and 7Ma ago, respectively. Migration directions and pool forming models are: Fluid type II migrated towards westnorth and northeast respectively to form structural and lithologic reservoirs; Fluid type II migrated to areas surrounding the sag and formed block faulted and buried hill reservoirs; Fluid type III migrated to slopes to form anticlinal reservoirs.

Marine Chemistry of the Permian Phosphoria Formation and Basin, Southeast Idaho

Major components in the Meade Peak Member of the Phosphoria Formation are apatite, dolomite, calcite, organic matter, and biogenic silica—a marine fraction; and aluminosilicate quartz debris—a terrigenous fraction. Samples from Enoch Valley, in southeast Idaho, have major element oxide abundances of Al2O3, Fe2O3, K2O, and TiO2 that closely approach the composition of the world shale average. Factor analysis further identifies the partitioning of several trace elements—Ba, Ga, Li, Sc, and Th and, at other sites in southeast Idaho and western Wyoming, B, Co, Cs, Hf, Rb, and Ta—totally into this fraction. Trace elements that fail to show such correlations or factor loadings include Ag, As, Cd, Cr, Cu, Mo, Ni, Se, the rare earth elements (REE), U, V, and Zn. Their terrigenous contribution is determined from minimum values of trace elements versus the terrigenous fraction. These minima too define trace element concentrations in the terrigenous fraction that approximately equal their concentrations in the world shale average. The marine fraction of trace elements represents the difference between the bulk trace element content of a sample and the terrigenous contribution. Of the trace elements enriched above a terrigenous contribution, Ag, Cr, Cu, Mo, and Se show strong loadings on the factor with an organic matter loading and U and the REE on the factor with a strong apatite loading. Cd, Ni, V, and Zn do not show a strong correlation with any of the marine components but are, nonetheless, strongly enriched above a terrigenous contribution. Interelement relationships between the trace elements identify two seawater sources—planktonic debris and basinal bottom water. Relationships between Cd, Cu, Mo, Zn, and possibly Ni and Se suggest a solely biogenic source. Their accumulation rates, and that of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(PO_{4}^{3{\mbox{--}}}\) \end{document}, further identify the level of primary productivity as having been moderate and the residence time of water in the basin at 4.5 yr. Enrichments of Cr, U, V, and the REE, above both terrigenous and biogenic contributions, define bottom-water redox conditions as having been oxygen depleted, that is, denitrifying but not sulfate reducing.

Beach sands from Baja California Peninsula, Mexico

Fifty beach locations were sampled in Baja California Peninsula, México, in order to characterize textural and compositional parameters. The western beach sands are mainly associated with a lower relief coastal plain and high energy of waves and currents with the beach sands of the eastern littoral zone. Finer, better sorted and low carbonate and rich quartz and feldspar contents are observed for the western beach sands when compared to the eastern beach sands. The mineralogical maturity and provenance index are greater for the western beach sands than for the eastern beach sands. These contrasts may be explained by differences on coastal plain relief and differences on hydrodynamic energy of waves and currents that are responsible for the rock fragment dilution by enrichment of more stable quartz debris. Finally, some distinctions were found for Na 2O–K 2O–CaO values. This is thought to be a result of the presence of some samples from the eastern coastline with higher values in CaO content, probably due to the presence of basaltic rocks.