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At least 325 records · Page 18

Adsorptive exchange of coccolith biominerals facilitates viral infection

Marine coccolithophores are globally distributed, unicellular phytoplankton that produce nanopatterned, calcite biominerals (coccoliths). These biominerals are synthesized internally, deposited into an extracellular coccosphere, and routinely released into the external medium, where they profoundly affect the global carbon cycle. The cellular costs and benefits of calcification remain unresolved. Here, we show observational and experimental evidence, supported by biophysical modeling, that free coccoliths are highly adsorptive biominerals that readily interact with cells to form chimeric coccospheres and with viruses to form “viroliths,” which facilitate infection. Adsorption to cells is mediated by organic matter associated with the coccolith base plate and varies with biomineral morphology. Biomineral hitchhiking increases host-virus encounters by nearly an order of magnitude and can be the dominant mode of infection under stormy conditions, fundamentally altering how we view biomineral-cell-virus interactions in the environment.

59 BASIC BIOLOGICAL SCIENCES↗

Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.

79 ASTRONOMY AND ASTROPHYSICS↗

Wide-blocky veins explained by dependency of crystal growth rate on fracture surface type: Insights from phase-field modeling

Vein microstructures contain a wealth of information on coupled chemical and mechanical processes of fracturing, fluid transport, and crystal growth. Numerical simulations have been used for exploring the factors controlling the development of vein microstructures; however, they have not been quantitatively validated against natural veins. Here we combined phase-field modeling with microtextural analysis of previously unexplained wide-blocky calcite veins in natural limestone and of the fresh fracture surface in this limestone. Results show that the wide-blocky vein textures can only be reproduced if ~10%–20% of crystals grow faster than the rest. This fraction corresponds to the amount of transgranularly broken grains that were observed on the experimental fracture surfaces, which are dominantly intergranular. We hypothesize that transgranular fractures allow faster growth of vein minerals due to the lack of clay coatings and other nucleation discontinuities that are common along intergranular cracks. Our simulation results show remarkable similarity to the natural veins and reproduce the nonlinear relationship between vein crystal width and vein aperture. This allows accurate simulations of crystal growth processes and related permeability evolution in fractured rocks.

Geology↗

The nature and origins of decametre-scale porosity in Ordovician carbonate rocks, Halahatang oilfield, Tarim Basin, China

At >7 km depths in the Tarim Basin, hydrocarbon reservoirs in Ordovician rocks of the Yijianfang Formation contain large cavities ( c . 10 m or more), vugs, fractures and porous fault rocks. Although some Yijianfang Formation outcrops contain shallow (formed near surface) palaeokarst features, cores from the Halahatang oilfield lack penetrative palaeokarst evidence. Outcrop palaeokarst cavities and opening-mode fractures are mostly mineral filled but some show evidence of secondary dissolution and fault rocks are locally highly ( c . 30%) porous. Cores contain textural evidence of repeated formation of dissolution cavities and subsequent filling by cement. Calcite isotopic analyses indicate depths between c . 220 and 2000 m. Correlation of core and image logs shows abundant cement-filled vugs associated with decametre-scale fractured zones with open cavities that host hydrocarbons. A Sm–Nd isochron age of 400 ± 37 Ma for fracture-filling fluorite indicates that cavities in core formed and were partially cemented prior to the Carboniferous, predating Permian oil emplacement. Repeated creation and filling of vugs, timing constraints and the association of vugs with large cavities suggest dissolution related to fractures and faults. In the current high-strain-rate regime, corroborated by velocity gradient tensor analysis of global positioning system (GPS) data, rapid horizontal extension could promote connection of porous and/or solution-enlarged fault rock, fractures and cavities. Supplementary material: Stable isotopic analyses and the velocity gradient tensor and principal direction and magnitude calculation are available at https://doi.org/10.6084/m9.figshare.c.4946046 Thematic collection: This article is part of the The Geology of Fractured Reservoirs collection available at: https://www.lyellcollection.org/cc/the-geology-of-fractured-reservoirs

Geology↗

Fracture, Dissolution, and Cementation Events in Ordovician Carbonate Reservoirs, Tarim Basin, NW China

Ordovician carbonate rocks of the Yijianfang Formation in the Tabei Uplift, Tarim Basin, contain deeply buried (>6000 m), highly productive oil and gas reservoirs associated with large cavities (>10 m). Previous workers inferred that large cavities are paleocaves (paleokarst) formed near the surface and subsequently buried. Alternately, caves may have formed by dissolution at depth along faults. Using 227 samples from 16 cores, we document textures and cement compositions bearing on cavity histories with petrographic, high-resolution scanning electron microscopy (SEM), isotopic, and fluid inclusion microthermometric observations. Results show that dissolution occurred at depth and was caused by (1) acidic fluids derived from Middle-Late Silurian and/or Devonian-Permian hydrocarbon generation and maturation, (2) high-temperature fluids, of which some were associated with Late Permian igneous activity, and (3) Mg-rich fluids that accompanied Jurassic-Cretaceous deformation and the formation of partially open fractures and stylobreccias (fault breccias). The relative paragenetic sequence of the structure-related diagenesis suggests seven stages of fracturing, dissolution, and cementation. Mottle fabrics in the Yijianfang Formation contain argillaceous carbonate-rich silt and are bioturbation features formed within the marine environment. Those mottled fabrics differ from clearly karstic features in the overlying Lianglitage Formation, which formed by near-surface dissolution and subsequent infilling of cavities by allochthonous sediment. Mottle fabrics are crosscut by compacted fractures filled with phreatic-vadose marine cements and followed by subsequent generations of cement-filled fractures and vugs indicating that some fractures and vugs became cement filled prior to later dissolution events. Calcite cements in fractures and vugs show progressively depleted values of δ18O documenting cement precipitation within the shallow (~220 m), intermediate (~625 m), and deep (~2000 m) diagenetic environments. Deep (mesogenetic) dissolution associated with fractures is therefore the principal source of the high porosity-permeability in the reservoir, consistent with other pieces of evidence for cavities localized near faults.

58 GEOSCIENCES↗

QED: A Powerful Query Equivalence Decider for SQL

Checking query equivalence is of great significance in database systems. Prior work in automated query equivalence checking sets the first steps in formally modeling and reasoning about query optimization rules, but only supports a limited number of query features. In this paper, we present Qed, a new framework for query equivalence checking based on bag semantics. Qed uses a new formalism called Q-expressions that models queries using different normal forms for efficient equivalence checking, and models features such as integrity constraints and NULLs in a principled way unlike prior work. Our formalism also allows us to define a new query fragment that encompasses many real-world queries with a complete equivalence checking algorithm, assuming a complete first-order theory solver. Empirically, Qed can verify 299 out of 444 query pairs extracted from the Calcite framework and 979 out of 1287 query pairs extracted from CockroachDB, which is more than 2× the number of cases proven by prior state-of-the-art solver.

Computer Science↗

Fracture Description of the HFTS-2 Slant Core, Delaware Basin, West Texas

Previous work in the Midland Basin Hydraulic Fracture Test Site project (HFTS1) has shown the value of core recovered from a stimulated volume in providing information on the geometry and extent of hydraulic fractures. This project (HFTS2) is in the Wolfcamp Formation of the Delaware Basin. A slant core through the stimulated volume was acquired above and below a stimulated well and the results of the fracture description are presented here. Here, nine, 3-inch-diameter whole cores from the slant well were examined for fractures prior to slabbing, together with a CT scan of the core. We used criteria developed during the HFTS1 project to identify hydraulic, natural, drilling-induced and core-handling fractures. Material collected from a few fracture faces was cleaned, sieved, and examined under a microscope to look for proppant. A total of 1261 fractures, including 500 hydraulic fractures, were described in 948 feet of core. Hydraulic fractures are not evenly distributed through the cores; they tend to occur in clusters. Many are remarkably planar, smooth, and featureless, while others have twist hackles, steps, plumose, and kinks. Natural, subvertical fractures, mostly less than 1 mm in width, sealed with blocky calcite, are oriented NE-SW (Set 1) and WNW-ESE (Set 2). Two Set 1 fractures have drusy cement on parted faces and were possibly open prior to drilling. A few subvertical sealed fractures with different orientations are also present. Bed-parallel natural fractures, most having fibrous cement (beef), and some showing top-to-north bed-parallel shear are present. Faults with normal/oblique movement were found in one part of the core. Drilling induced and core-handling breaks were identified in all cores, and were also noted to have reactivated some natural fractures. The results from this work will allow hydraulic fracture distribution relative to the stimulated well to be assessed. The number of fractures is generally greater than the number of perforations, but these can be compared for different stages and perforation clusters. Surface features provide information about the direction of hydraulic fracture propagation and about segmentation and bifurcation that might increase the number of fracture strands. Reactivation of natural fractures, including bedding-parallel fractures, occurs although the mechanism of parting is mostly unknown. The wider HFTS2 project will make use of this fracture description to improve hydraulic fracture modeling (geomechanics and engineering), to help explain pressure depletion and fiber optics observations (reservoir depletion and frac geometry), to help verify indirect fracture diagnostic techniques such as microseismic monitoring (geophysics), and to help calibrate horizontal well image logs.

58 GEOSCIENCES↗

Materials Data on LiNbO3 by Materials Project

LiNbO3 is Calcite structured and crystallizes in the trigonal R3c space group. The structure is three-dimensional. Li1+ is bonded to six equivalent O2- atoms to form distorted LiO6 pentagonal pyramids that share corners with three equivalent NbO6 octahedra, corners with six equivalent LiO6 pentagonal pyramids, edges with three equivalent NbO6 octahedra, and a faceface with one NbO6 octahedra. The corner-sharing octahedral tilt angles are 62°. There are three shorter (2.09 Å) and three longer (2.27 Å) Li–O bond lengths. Nb5+ is bonded to six equivalent O2- atoms to form distorted NbO6 octahedra that share corners with six equivalent NbO6 octahedra, corners with three equivalent LiO6 pentagonal pyramids, edges with three equivalent LiO6 pentagonal pyramids, and a faceface with one LiO6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 41°. There are three shorter (1.90 Å) and three longer (2.18 Å) Nb–O bond lengths. O2- is bonded in a distorted see-saw-like geometry to two equivalent Li1+ and two equivalent Nb5+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on LaSc3(BO3)4 by Materials Project

LaSc3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. La3+ is bonded to six equivalent O2- atoms to form distorted LaO6 pentagonal pyramids that share corners with six equivalent ScO6 octahedra. The corner-sharing octahedral tilt angles are 61°. All La–O bond lengths are 2.49 Å. Sc3+ is bonded to six O2- atoms to form ScO6 octahedra that share corners with two equivalent LaO6 pentagonal pyramids and edges with two equivalent ScO6 octahedra. There are a spread of Sc–O bond distances ranging from 2.08–2.15 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) B–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one B3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one La3+, one Sc3+, and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on YbAl3(BO3)4 by Materials Project

YbAl3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Yb3+ is bonded to six equivalent O2- atoms to form distorted YbO6 pentagonal pyramids that share corners with six equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 60°. All Yb–O bond lengths are 2.38 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent YbO6 pentagonal pyramids and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–1.95 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.39 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.38 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Yb3+, one Al3+, and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on MgSn(BO3)2 by Materials Project

MgSn(BO3)2 is Calcite-derived structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent O2- atoms to form MgO6 octahedra that share corners with six equivalent SnO6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Mg–O bond lengths are 2.14 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. Sn4+ is bonded to six equivalent O2- atoms to form SnO6 octahedra that share corners with six equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Sn–O bond lengths are 2.10 Å. O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one B3+, and one Sn4+ atom.

36 MATERIALS SCIENCE↗

Materials Data on TmAl3(BO3)4 by Materials Project

TmAl3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Tm3+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Tm–O bond lengths are 2.31 Å. Al3+ is bonded to six O2- atoms to form edge-sharing AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.94 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.38 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Tm3+, one Al3+, and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on CaSn(BO3)2 by Materials Project

CaSn(BO3)2 is Calcite-derived structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent O2- atoms to form CaO6 octahedra that share corners with six equivalent SnO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Ca–O bond lengths are 2.40 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. Sn4+ is bonded to six equivalent O2- atoms to form SnO6 octahedra that share corners with six equivalent CaO6 octahedra. The corner-sharing octahedral tilt angles are 58°. All Sn–O bond lengths are 2.09 Å. O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one B3+, and one Sn4+ atom.

36 MATERIALS SCIENCE↗

Materials Data on GdAl3(BO3)4 by Materials Project

GdAl3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Gd3+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Gd–O bond lengths are 2.36 Å. Al3+ is bonded to six O2- atoms to form edge-sharing AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–1.96 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.39 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Gd3+, one Al3+, and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on CeSc3(BO3)4 by Materials Project

CeSc3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Ce3+ is bonded to six equivalent O2- atoms to form distorted CeO6 pentagonal pyramids that share corners with six equivalent ScO6 octahedra. The corner-sharing octahedral tilt angles are 60°. All Ce–O bond lengths are 2.47 Å. Sc3+ is bonded to six O2- atoms to form ScO6 octahedra that share corners with two equivalent CeO6 pentagonal pyramids and edges with two equivalent ScO6 octahedra. There are a spread of Sc–O bond distances ranging from 2.08–2.15 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) B–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one B3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ce3+, one Sc3+, and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on PrSc3(BO3)4 by Materials Project

PrSc3(BO3)4 is Calcite-derived structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Pr3+ is bonded to six O2- atoms to form distorted PrO6 pentagonal pyramids that share corners with six ScO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are four shorter (2.46 Å) and two longer (2.48 Å) Pr–O bond lengths. There are two inequivalent Sc3+ sites. In the first Sc3+ site, Sc3+ is bonded to six O2- atoms to form ScO6 octahedra that share corners with two equivalent PrO6 pentagonal pyramids and edges with two ScO6 octahedra. There are a spread of Sc–O bond distances ranging from 2.07–2.15 Å. In the second Sc3+ site, Sc3+ is bonded to six O2- atoms to form ScO6 octahedra that share corners with two equivalent PrO6 pentagonal pyramids and edges with two equivalent ScO6 octahedra. There are a spread of Sc–O bond distances ranging from 2.08–2.16 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. All B–O bond lengths are 1.39 Å. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) B–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Sc3+ and one B3+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Pr3+, one Sc3+, and one B3+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Pr3+, one Sc3+, and one B3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Pr3+, one Sc3+, and one B3+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Sc3+ and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on NdFe3(BO3)4 by Materials Project

NdFe3(BO3)4 is Calcite-derived structured and crystallizes in the trigonal R32 space group. The structure is three-dimensional. Nd3+ is bonded to six equivalent O2- atoms to form distorted NdO6 pentagonal pyramids that share corners with six equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 60°. All Nd–O bond lengths are 2.43 Å. Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent NdO6 pentagonal pyramids and edges with two equivalent FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.99–2.07 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Nd3+, one Fe3+, and one B3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Fe3+ and one B3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Fe3+ and one B3+ atom.

36 MATERIALS SCIENCE↗

Materials Data on VBO3 by Materials Project

VBO3 is Calcite structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. V3+ is bonded to six equivalent O2- atoms to form corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles are 55°. All V–O bond lengths are 2.07 Å. B3+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All B–O bond lengths are 1.39 Å. O2- is bonded in a distorted trigonal planar geometry to two equivalent V3+ and one B3+ atom.

36 MATERIALS SCIENCE↗