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Tectonic Control (tectonic + control)

Distribution by Scientific Domains

Earth and Environmental Science	83%

Selected Abstracts

Tectonic Controls on the Formation of the Liwu Cu-rich Sulfide Deposit in the Jianglang Dome, S W China

RESOURCE GEOLOGY, Issue 2 2003
Dan-Ping Yan
Abstract. The Liwu Cu-rich sulfide deposit occurs within the Jianglang dome in the eastern margin of the Tibetan plateau. The dome consists of a core, a middle slab and a cover sequence. The main deposit is hosted in the core with minor ore bodies in the middle slab. The protolith of the core consists of clastic sedimentary rocks with inter-layered volcanic rocks. All of the ore bodies are substantially controlled by an extensional detachment fault system. The ore bodies within the core are distributed along the S2 foliation in the hinge of recumbent fold (D2), whereas ore bodies with en echelon arrangement are controlled by the mylonitic foliation of the lower detachment fault. Ore bodies within the middle slab are oriented with their axes parallel to the mylonitic foliation. Pyrite and pyrrhotite from the ores contain Co ranging from 37 to 1985 ppm, Ni from 2.5 to 28.1 ppm, and Co/Ni ratios from 5 to 71. These sulfides have ,34S values ranging from 1.5 to 7.5 % whereas quartz separates have ,18O values of 11.9 and 14.3 % and inclusion fluid in quartz has ,D value of-88.1 %. These features suggest that the deposit was of hydrothermal origin. Two ore-forming stages are recognized in the evolution of the Jianglang dome. (1) A low-temperature ore-forming process, during the tectonic transport of the upper plate above the lower detachment, and the initial phase of the footwall updom-ing at 192,177 Ma. (2) A medium-temperature ore-forming stage, related to the final structural development of the initial detachment at 131,81Ma. Within the core, the ore bodies of the first stage were uplifted to, or near, the brittle/ductile horizon where the ore-forming metals were re-concentrated and enriched. A denudation stage in which a compressional tectonic event produced eastward thrusting overprinted the previous structures, and finally denuded the deposit. The Liwu Cu-rich sulfide deposit was formed during a regional extensional tectonic event and is defined as a tectono-strata-bound hydrothermal ore deposit. [source]

Tectonic control of erosion and sedimentation in the Amazon Basin of Bolivia

HYDROLOGICAL PROCESSES, Issue 22 2009
Patrice Baby
Abstract The western Amazon drainage basin, which extends from southern Colombia to northern Bolivia, comprises the Cordillera Oriental of the Andes and its adjacent foreland basin system. In northern Bolivia, the orogenic wedge of the eastern Andes is very large, and its forward propagation controls the morphology of the Madeira drainage basin. We consider here the erosion and sedimentation mass balance in this part of the Amazon Basin, estimated on the basis of recent sediment yield data, within the current tectonic and geomorphic framework. The total suspended sediment (TSS) flux exported from the present orogenic wedge of northern Bolivia has been estimated at 500,600 million t year,1. More than 50% of the total sediment load crossing the Madeira foreland basin system is deposited. The rest of the sediments (less than 46%) reaches the eastern Amazon Basin, bypassing the Brazilian craton to the north. The average mass of sediment that has been deposited from the late Miocene to the present in the Madeira foreland basin sedimentation system is less than that intercepted today, by a factor of about 2·4. These results can be interpreted as an increase in Bolivian foreland basin flexural subsidence over time, associated with crust thickening and orogenic loading, and accentuated by the growing mass of retained sediments. They are consistent with the uplift rates of the Cordillera Oriental, obtained from fission-track dating, which began increasing significantly around 10,15 Ma. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Tectonic control of bioalteration in modern and ancient oceanic crust as evidenced by carbon isotopes

ISLAND ARC, Issue 1 2006
Harald Furnes
Abstract We review the carbon-isotope data for finely disseminated carbonates from bioaltered, glassy pillow rims of basaltic lava flows from in situ slow- and intermediate-spreading oceanic crust of the central Atlantic Ocean (CAO) and the Costa Rica Rift (CRR). The ,13C values of the bioaltered glassy samples from the CAO show a large range, between ,17 and +3, (Vienna Peedee belemnite standard), whereas those from the CRR define a much narrower range, between ,17, and ,7,. This variation can be interpreted as the product of different microbial metabolisms during microbial alteration of the glass. In the present study, the generally low ,13C values (less than ,7,) are attributed to carbonate precipitated from microbially produced CO2 during oxidation of organic matter. Positive ,13C values >0, likely result from lithotrophic utilization of CO2 by methanogenic Archaea that produce CH4 from H2 and CO2. High production of H2 at the slow-spreading CAO crust may be a consequence of fault-bounded, high-level serpentinized peridotites near or on the sea floor, in contrast to the CRR crust, which exhibits a layer-cake pseudostratigraphy with much less faulting and supposedly less H2 production. A comparison of the ,13C data from glassy pillow margins in two ophiolites interpreted to have formed at different spreading rates supports this interpretation. The Jurassic Mirdita ophiolite complex in Albania shows a structural architecture similar to that of the slow-spreading CAO crust, with a similar range in ,13C values of biogenic carbonates. The Late Ordvician Solund,Stavfjord ophiolite complex in western Norway exhibits structural and geochemical evidence for evolution at an intermediate-spreading mid-ocean ridge and displays ,13C signatures in biogenic carbonates similar to those of the CRR. Based on the results of this comparative study, it is tentatively concluded that the spreading rate-dependent tectonic evolution of oceanic lithosphere has a significant control on the evolution of microbial life and hence on the ,13C biosignatures preserved in disseminated biogenic carbonates in glassy, bioaltered lavas. [source]

Volcanic and Tectonic Framework of the Hydrothermal Activity of the Izu,Bonin Arc

RESOURCE GEOLOGY, Issue 3 2008
Osamu Ishizuka
Abstract In the Izu,Bonin Arc, hydrothermal activities have been reported from volcanoes along present-day volcanic front, a rear arc volcano and a back-arc rift basin as well as a remnant arc structure now isolated from the Quaternary arc. It is widely known that characteristics of hydrothermal activity (mineralogy, chemistry of fluid etc.) vary depending upon its tectonic setting. The Izu,Bonin Arc has experienced repeated back-arc or intra-arc rifting and spreading and resumption of arc volcanism. These characteristics make this arc system a suitable place to study the tectonic control on hydrothermal activity. The purpose of the present paper is, therefore, to summarize volcanotectonic setting and history of the Izu,Bonin Arc in relation to the hydrothermal activity. The volcanotectonic history of the Izu,Bonin Arc can be divided into five stages: (i) first arc volcanism (boninite, high-Mg andesite), 48,46 Ma; (ii) second arc volcanism (tholeiitic, calc-alkaline), 44,29 Ma; (iii) first spreading of back-arc basin (Shikoku Basin), 25,15 Ma; (iv) third arc volcanism (tholeiitic, calc-alkaline), 13,3 Ma; and (v) rifting in the back-arc and tholeiitic volcanism along the volcanic front, 3,0 Ma. Magmas erupted in each stage of arc evolution show different chemical characteristics from each other, mainly due to the change in composition of slab-derived component and possibly mantle depletion caused by melt extraction during back-arc spreading and prolonged arc volcanism. In the volcanotectonic context summarized here, hydrothermal activity recognized in the Izu,Bonin Arc can be classified into four groups: (i) present-day hydrothermal activity at the volcanic front; (ii) active hydrothermal activity in the back arc; (iii) fossil hydrothermal activity in the back-arc volcanoes; and (iv) fossil hydrothermal activity in the remnant arc. Currently hydrothermal activities occur in three different settings: submarine caldera and stratocones along the volcanic front; a back-arc rift basin; and a rear arc caldera. In contrast, hydrothermal activities found in the back-arc seamount chains were associated with rear arc volcanism in Neogene after cessation of back-arc spreading of the Shikoku Basin. Finally, sulfide mineralization associated with boninitic volcanism in the Eocene presumably took place during forearc spreading in the initial stage of the arc. This type of activity appears to be limited during this stage of arc evolution. [source]

Tectono-sedimentary evolution of active extensional basins

BASIN RESEARCH, Issue 3-4 2000
R. L. Gawthorpe
We present conceptual models for the tectono-sedimentary evolution of rift basins. Basin architecture depends upon a complex interaction between the three-dimensional evolution of basin linkage through fault propagation, the evolution of drainage and drainage catchments and the effects of changes in climate and sea/lake level. In particular, the processes of fault propagation, growth, linkage and death are major tectonic controls on basin architecture. Current theoretical and experimental models of fault linkage and the direction of fault growth can be tested using observational evidence from the earliest stages of rift development. Basin linkage by burial or breaching of crossover basement ridges is the dominant process whereby hydrologically closed rifts evolve into open ones. Nontectonic effects arising from climate, sea or lake level change are responsible for major changes in basin-scale sedimentation patterns. Major gaps in our understanding of rift basins remain because of current inadequacies in sediment, fault and landscape dating. [source]

Tectonic,Hydrocarbon Accumulation of Laoyemiao Region in the Nanpu Sag, Bohai Bay Basin

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009
Cuimei ZHANG
Abstract: This paper aims to gain insight into Laoyemiao (LYM) tectonic features and utilizes the tectonic,hydrocarbon accumulation model by integrated analysis tectonic controls on suitable reservoirs, trap styles, and hydrocarbon migration. On the basis of 3-D seismic data interpretation and the Xi'nanzhuang (XNZ) Fault geometry analysis, it has been assessed that the LYM tectonics is essentially a transverse anticline produced by flexure of the XNZ Fault surface and superimposed by Neocene north-east-trending strike-slip faults. Transverse anticline is found to exert controls both on major sediment transportation pathways and sedimentary facies distribution. Fan-delta plains that accumulated on the anticline crest near the XNZ Fault scrap and fan-delta front on the anticline front and the upper part of both limbs slumps on synclines and the Linque subsag. In combination with the reservoir properties, suitable reservoirs are predicted in the subfacies of subaqueous distributary channel and mouth bar deposited on the anticline crest. The LYM-faulted anticline accounts for the following trap groups: faulted-block and anticline-dominated trap, fault-dominated traps, and combined and stratigraphic traps. Evidence from biomarkers of crude oil and hydrocarbon-filling period simultaneous, or a little later to the strike-slip fault activity, reveal that the strike-slip faults penetrating into the deep source rock, by connecting with shallow reservoirs, provide the major hydrocarbon migration pathways. [source]