Hassan A. Babaie

Geochemistry of arc volcanic rocks of the Zagros Crush Zone, Neyriz, Iran

Abstract The northeastern margin of the Tethyan Neyriz ophiolite complex in southwestern Iran is tectonically juxtaposed under cataclastically-deformed island arc volcanic–volcaniclastic rocks. We document this arc component of the Zagros Crush Zone in the Neyriz area, and describe its petrographic and geochemical characteristics. The arc unit which we call the Hassanabad Unit, is tectonically intercalated with Cretaceous limestone in the cataclastic shear zone around the Hassanabad pass north of Neyriz. Analyses of the distributions of the major, rare earth and other trace elements in the volcanic rocks of the Hassanabad Unit reveal a dominantly calc-alkaline island arc composition. Volcanogenic sandstone and sedimentary breccia, with clasts of basalt, andesite and diorite, are cataclastically intercalated with pillowed calc-alkaline island arc volcanic rocks, pelagic limestone and radiolarian chert. Trace element geochemistry corroborates the petrographic evidence that the poorly-sorted and angular volcanogenic sediments were derived locally from the island arc volcanic and intrusive rocks. The emplacement of the volcanic arc rocks adjacent to the thrust sheets of the crustal and mantle sequences of the Neyriz ophiolite was probably a result of subduction-related processes during closure of the Tethys ocean during the Late Cretaceous.

Developing a modular hydrogeology ontology by extending the SWEET upper-level ontologies

Upper-level ontologies comprise general concepts and properties which need to be extended to include more diverse and specific domain vocabularies. We present the extension of NASAs Semantic Web for Earth and Environmental Terminology (SWEET) ontologies to include part of the hydrogeology domain. We describe a methodology that can be followed by other allied domain experts who intend to adopt the SWEET ontologies in their own discipline. We have maintained the modular design of the SWEET ontologies for maximum extensibility and reusability of our ontology in other fields, to ensure inter-disciplinary knowledge reuse, management, and discovery. The extension of the SWEET ontologies involved identification of the general SWEET concepts (classes) to serve as the super-class of the domain concepts. This was followed by establishing the special inter-relationships between domain concepts (e.g., equivalence for vadose zone and unsaturated zone), and identifying the dependent concepts such as physical properties and units, and their relationship to external concepts. Ontology editing tools such as SWOOP and Protege were used to analyze and visualize the structure of the existing OWL files. Domain concepts were introduced either as standalone new classes or as subclasses of existing SWEET ontologies. This involved changing the relationships (properties) and/or adding new relationships based on domain theories. In places, in the Owl files, the entire structure of the existing concepts needed to be changed to represent the domain concept more meaningfully. Throughout this process, the orthogonal structure of SWEET ontologies was maintained and the consistency of the concepts was tested using the Racer reasoner. Individuals were added to the new concepts to test the modified ontologies. Our work shows that SWEET ontologies can successfully be extended and reused in any field without losing their modular or reference structure, or disrupting their URI links.

Semibrittle and cataclastic deformation of hornblende-quartz rocks in a ductile shear zone

Abstract Hornblende-quartz rock of the Coniston Shear Zone I (CSZ I) at the Grenville front, Canada, was deformed dominantly by semibrittle flow of hornblende-quartz aggregate and locally by cataclastic flow of hornblende aggregates. Fracturing and slip along fractures produced mesoscopic domino-style deformation. Void formation associated with domino-style deformation was prevented by leveling the corners of the slid segments of individual mesodominoes, producing narrow shear zones. The shear zones eventually coalesced to form the dominant mylonitic C-foliation. On the microscopic scale, semibrittle flow was achieved by dynamic recrystallization of quartz concomitant with microcracking and microfaulting of hornblende into microdominoes, and rotation, shear and separation of the microdominoes. Plastic deformation of quartz accommodated the rotation and shear of the microdominoes, thereby obviating the space problem. Local cataclastic flow occurred in the hornblende domains and produced R 1 Riedel shear surfaces. The observed processes are consistent with greenschist-grade retrograde metamorphism accompanying post-orogenic uplift along this zone.

Development of interlaced mylonites, cataclasites and breccias: example from the Towaliga fault, south central Appalachians

Abstract A variety of cataclastic rocks from crush breccias to cataclasites and silicified breccias are associated with retrograde mylonites along the Towaliga fault zone of south central Appalachians in Georgia. A zone of alternating breccias and quartz ultra-mylonites, bordered by quartz mylonites that are roughly laminated with mm-scale mica-rich bands of cataclasites, occur subparallel to the mylonitic foliation. Elsewhere along the fault zone, evidence for plastically deformed microfractures is found. In discussing the mechanical evolution of these rocks two possibilities are considered: (a) the cataclasis is an overprint representing deformation in an entirely brittle regime; and (b) cataclasis and mylonitization occurred at T > 300° C in a predominantly plastic regime. Within the framework of the latter model it is suggested that the cataclasite bands are either due to the relaxation of dilational stresses following downward propagation of seismic ruptures or represent strain-induced seismic instabilities during plastic shearing.

Modeling geological objects with the XML Schema

Interchange, storage, and management of geological data require the development of knowledge-based, standardized vocabularies and data structures. Concepts modeled and designed with the Unified Markup Language (UML), can be mapped into XML Schema Definition Language (XSDL) to compose modular markup languages for each discipline. Developing such efficient, intra-disciplinary, modular and reusable components, based on the XSDL namespace facility and the principles of object-oriented design, reduces redundancy, increases efficiency, scalability, and extensibility, and simplifies the maintenance and future extension of the code. This paper discusses the best practices of composition and reuse of modular intra-disciplinary components by applying XML Schema namespace syntax. In addition to several small examples given for a variety of geological cases, the paper constructs a UML conceptual model and markup language, applying an XML-type library, for a component of the plate tectonics knowledge base (TectonicsML) that deals with the divergent plate boundary.

Geology, petrology and tectonomagmatic evolution of the plutonic crustal rocks of the Sabzevar ophiolite, NE Iran

The plutonic crustal sequence exposed northeast of Sabzevar is part of the ophiolitic belt of Sabzevar that occurs along the northern margin of the Central Iran micro-continent. The sequence includes olivine and pyroxene gabbro with cumulate characteristics, isotropic gabbro, foliated gabbro and a diabase sheeted dyke complex cut by wehrlite and olivine websterite intrusions, and pegmatite gabbro and plagiogranite as small intrusions and dykes. The sequence is comparable to gabbros in known ophiolite complexes. Microscopic studies show an abundance of the mesocumulate and heteradcumulate textures that represent open system magma chambers, which are common in supra-subduction zones. The olivine → plagioclase → clinopyroxene → ± orthopyroxene → amphibole trend of mineralization in the gabbros, similar to mid-ocean ridge basalt (MORB), and olivine → clinopyroxene → ± orthopyroxene → plagioclase → amphibole, similar to arc rocks, indicate the diversity in the formation of these rocks, and represent petrographic evidence of their formation in a supra-subduction zone. The rocks have calc-alkaline to tholeiitic affinities, and niobium depletion in the spider diagrams of diabase that matches the patterns of island arc magma. These patterns, and the light rare earth element enrichment of the diabase and plagiogranite, suggest the effect and introduction of the fluids, originating from the subducting slab, beneath the mantle wedge. The low titanium compositions, matching those of arc diabase and plagiogranite, plot in the island arc to MORB tectonomagmatic fields, and suggest formation of the Sabzevar ophiolitic plutonic crustal sequence in a supra-subduction zone during Late Cretaceous time.

Developing the earthquake markup language and database with UML and XML schema

Seismic information is commonly shared across networks, and stored in heterogeneous databases that are maintained by different and autonomous groups. Because the metadata of the seismic information is generally not structured, information loss commonly occurs when data is transmitted from one source to another. Minimizing such information loss and enhancing information interchange over the Web require construction of specific markup languages for each part of seismology. The sub-disciplinary data syntax and vocabularies allow construction of corresponding relational databases to store and interchange the structured data. Developing modular data structures and databases for each sub-discipline allows composition of new languages through reuse, and enables future extension of the vocabulary and maintenance of the knowledge base. In this paper, we show how to design the conceptual and logical models for a small set of seismology that deals with earthquake (EarthquakeML). We discuss the application of the UML to the design and mapping of the object model into W3 XML Schema and database. The emphasis is on designing components that can be reused across discipline, and reduce redundancies by developing type libraries. We show how to map the XML schema into a relational data model; and implement the EarthquakeDB with the Microsoft Access DBMS.

Self-similar cataclasis in the Saltville thrust zone, Knoxville, Tennessee

Fault rocks from the Saltville thrust zone, Knoxville, Tennessee, display a fractal geometry of clast size over 3 orders of magnitude. The cataclastic fractal geometry occurs at each magnification in different clast size classes and at combined magnifications. The mean of the fractal dimension (D) measured at each of the optical photomicrographs is generally smaller than that of the scanning electron microscopy images because of the smaller clast density in the optical sections. The fractal dimensions measured on randomly selected areas of the sections cut parallel to the thrust and normal to the thrust along the dip and strike, show a normal distribution with its mean, median, and mode that correlate closely with the dimension of ideal, fractal cataclasis (DI) based on the Sierpinski carpet model. The cataclasis was a statistical random, isotropic, and homogeneous fractal process that deformed the carbonates similarly parallel and normal to the thrust plane and in different parts of the thrust zone.

Initiation of cataclastic flow and development of cataclastic foliation in nonporous quartzites from a natural fault zone

Abstract Microstructural study of foliated quartz cataclasites of a segment of the Towaliga fault zone, Georgia, USA, indicates that rock strain by cataclastic deformation occurred through microscopic displacements along a distributed system of shear bands. The localized cataclastic flow in the bands was in turn the result of frictional sliding along a network of mesoscopic shear fractures that accommodated initial strains and were in part created by high fluid pressures in the fault zone. The shear fractures at both the microscopic and mesoscopic scale were formed in the Riedel R1, P, and Y orientations. Simultaneous displacements along these Riedel shears produced the cataclastic foliation, rhomb-shaped and tabular quartz grain fabrics, and straight, stepped grain boundaries. Crystallization by fluids accompanied fracturing and possibly aided the cataclastic flow by forming muscovite and quartz crystals along fractures. Most fluid inclusion trails and quartz veins cut across the cataclastic features, indicating that fluids which assisted the deformation later healed the fractures. A right-lateral sense of displacement is suggested for the cataclastic flow, consistent with the kinematics of the mylonitization along the fault zone.

Source rock and maturation evaluation of the Barbados accretionary prism

Abstract Organic material in specimens from surface and downhole sites and samples of oil and gas from Barbadian wells were studied for source potential and maturation history. The study involved: (1) visual examination of the kerogen; (2) measurement of total organic carbon content; (3) determination of vitrinite reflectance; (4) Rock-Eval pyrolysis assay; (5) geochemical measurement of pooled and extracted bitumens including carbon isotopic ratios (δ 13 C); and (6) gas chromatographic analysis of saturated gaseous hydrocarbons. Two types of kerogen occur in Barbados: terrestrial, presumably of South American origin, and marine planktonic. The two types are mixed in most samples. The terrestrial kerogens are dominant and occur in all wells in the basal complex and most of its outcrops. The planktonic organic matter occurs in exposed melange, hemipelagic rocks and rarely in terrigenous turbidites. The well specimens do not show significant maturation within the drilled depths, suggesting that pooled hydrocarbons originated from deeper levels of the prism and accumulated as a result of migration. Faults bounding the intraprism thrust sheets probably provided migratory paths for hydrocarbons and water, juxtaposed rocks of variable maturity, assisted in alteration and biodegradation, and led to the formation of structural traps. The composition of gases indicates that maturation conditions for gas generation may exist at great depths within the Barbados accretionary prism.