Hasil untuk "Petrology"

T. Holland, R. Powell

C. Herzberg, K. Condie, J. Korenaga

A. Bouvier, J. Vervoort, P. Patchett

Fu-Yuan Wu, Jin-Hui Yang, Yigang Xu et al.

The North China Craton (NCC) was originally formed by the amalgamation of the eastern and western blocks along an orogenic belt at ∼1.9 Ga. After cratonization, the NCC was essentially stable until the Mesozoic, when intense felsic magmatism and related mineralization, deformation, pull-apart basins, and exhumation of the deep crust widely occurred, indicative of destruction or decratonization. Accompanying this destruction was significant removal of the cratonic keel and lithospheric transformation, whereby the thick (∼200 km) and refractory Archean lithosphere mantle was replaced by a thin (1.8 Ga). ▪ A craton is characterized by a rigid lithospheric root, which provides longevity and stability during its evolutionary history. ▪ Some cratons, such as the North China Craton, can be destroyed by losing their stability, manifested by magmatism, deformation, earthquake, etc.

T. Holland, R. Powell

J. Pearce, N. Harris, A. Tindle

Granites may be subdivided according to their intrusive settings into four main groups—ocean ridge granites (ORG), volcanic arc granites (VAG), within plate granites (WPG) and collision granites (COLG)—and the granites within each group may be further subdivided according to their precise settings and petrological characteristics. Using a data bank containing over 600 high quality trace element analyses of granites from known settings, it can be demonstrated using ORG-normalized geochemical patterns and element-SiO2 plots that most of these granite groups exhibit distinctive trace element characteristics. Discrimination of ORG, VAG, WPG and syn-COLG is most effective in Rb–Y–Nb and Rb–Yb–Ta space, particularly on projections of Y–Nb, Yb–Ta, Rb–(Y + Nb) and Rb–(Yb + Ta). Discrimination boundaries, though drawn empirically, can be shown by geochemical modelling to have a theoretical basis in the different petrogenetic histories of the various granite groups. Post-collision granites present the main problem of tectonic classification, since their characteristics depend on the thickness and composition of the lithosphere involved in the collision event and on the precise timing and location of magmatism. Provided they are coupled with a consideration of geological constraints, however, studies of trace element compositions in granites can clearly help in the elucidation of post-Archaean tectonic settings.

Guochun Zhao, Min Sun, S. Wilde et al.

T. Holland, R. Powell

M. H. Dodson

M. Drummond, Marc J. Defant

J. Zijderveld

K. Zong, R. Klemd, Yu Yuan et al.

Yong‐Fei Zheng, W. Xiao, Guochun Zhao

H. Rollinson, V. Pease

This textbook is a complete rewrite, and expansion of Hugh Rollinson's highly successful 1993 book Using Geochemical Data: Evaluation, Presentation, Interpretation. Rollinson and Pease's new book covers the explosion in geochemical thinking over the past three decades, as new instruments and techniques have come online. It provides a comprehensive overview of how modern geochemical data are used in the understanding of geological and petrological processes. It covers major element, trace element, and radiogenic and stable isotope geochemistry. It explains the potential of many geochemical techniques, provides examples of their application, and emphasizes how to interpret the resulting data. Additional topics covered include the critical statistical analysis of geochemical data, current geochemical techniques, effective display of geochemical data, and the application of data in problem solving and identifying petrogenetic processes within a geological context. It will be invaluable for all graduate students, researchers, and professionals using geochemical techniques.

A. Astort, E. Trasatti, Luca Caricchi et al.

Understanding and managing unrest at a volcano include i) ascertaining the magmatic distribution and migration, and ii) tracking the evolution of the shallow plumbing system. Here we use multi-technique geodetic data, mechanical models, and petrological simulations to define both aspects for the ongoing (2005-present) unrest at Campi Flegrei caldera, Italy. Results show a deformation source exhibiting progressive widening and shallowing, from 5.9 to 3.9 kilometres. Concurrently, a deeper tabular source at 8 km depth experiences limited but constant deflation. Petrological calculations explain inflation of the shallower source resulting from the rise of 0.06 to 0.22 cubic kilometres of magma from depth ≥8 kilometres. Our analysis provides strong evidence that magma ascent to depths shallower than 8 kilometres is the ultimate driver behind the ongoing unrest. This merging of geodetic and petrological approaches to track the evolution of a plumbing system better constrains magma ascent at volcanoes experiencing unrest. The unrest and surface deformation observed at Campi Flegrei caldera (Italy) between 2007 and 2023 are driven by magma ascent to depths shallower than eight kilometers, according to combined geodetic and petrologic simulations.

Mojtaba Homaie, Asadollah Mahboubi, Dan J. Hartmann et al.

Abstract Previous attempts to classify flow units in Iranian carbonate reservoirs, based on porosity and permeability, have faced challenges in correlating the rock's pore size distribution with the capillary pressure profile. The innovation of this study highlights the role of clustering techniques, such as Discrete Rock Type, Probability, Global Hydraulic Element, and Winland's Standard Chart in enhancing the reservoir's rock categorization. These techniques are integrated with established flow unit classification methods. They include Lucia, FZI, FZI*, Winland R35, and the improved stratigraphic modified Lorenz plot. The research accurately links diverse pore geometries to characteristic capillary pressure profiles, addressing heterogeneity in intricate reservoirs. The findings indicate that clustering methods can identify specific flow units, but do not significantly improve their classification. The effectiveness of these techniques varies depending on the flow unit classification method employed. For instance, probability-based methods yield surpassing results for low-porosity rocks when utilizing the FZI* approach. The discrete technique generates the highest number of flow unit classes but provides the worst result. Not all clustering techniques reveal discernible advantages when integrated with the FZI method. In the second part, the study creatively suggests that rock classification can be achieved by concurrently clustering irreducible water saturation (SWIR) and porosity in unsuccessful flow unit delineation cases. The SWIR log was estimated by establishing a smart correlation between porosity and SWIR in the pay zone, where water saturation and SWIR match. Then, the estimated saturation was dispersed throughout the reservoir. Subsequently, the neural network technique was employed to cluster and propagate the three finalized flow units. This methodology is an effective recommendation when conventional flow unit methods fail. The study also investigates influential factors causing the failure of flow unit classification methods, including pore geometry, oil wettability, and saturation in heterogeneous reservoirs.

Juncheng Zhang, Jun Li, Zhonghui Li et al.

Abstract The current extension limit prediction model for offshore extended-reach well (ERW) in mudstone does not consider the formation collapse, which poses a huge risk to offshore drilling construction. To address this problem, this paper presents new open-hole extension limit prediction model for ERW. By considering formation collapse, rate of penetration (ROP), and annular pressure loss, the extension limit models during normal drilling and tripping were derived. The sensitivity of geological and engineering factors was evaluated by analyzing limits for wells 1H and 2H. The research results showed that: (1) The extension limit increases with the ROP and formation collapse duration, but decreases with the increase in mud weight, plastic viscosity, and flow rate. (2) In ERWs, the mud flow rate has a significant impact on the extension limit than the plastic viscosity of mud fluid. However, mud weight has the least impact compared to the two. (3) Considering various parameters, the predicted extension limit of well 1H, when the mud weight is 1.16 g/cm3 [9.67 ppg], is 1593.28 m [5225.96 ft] less than the limit when the collapse period is not considered.

Xiaorui Yun, Ying Zhang, Dingyong Liang et al.

Hainan Island located at the southernmost tip of the continental crust of the South China Plate, has high terrestrial heat-flow values, widely-distributed hot springs, and rich geothermal resources. Intensified researches on the origin and potentials of geothermal resources can promote Hainan Island's development into a clean energy island. To determine the geological conditions for the formation of geothermal resources in southern Hainan Island, we collected core samples of granites from the Baocheng batholith in southern Hainan Island and conducted systematic analysis in respect of petrology, geochronology, geochemistry, and petrophysical property. The results of this study are as follows. The Baocheng batholith in the southern Hainan Island has a crystallization age of 98.42 ± 0.56 Ma, making it the product of magmatism in the early stage of the Late Cretaceous. It mainly consists of high-K calc-alkaline granites, which were intruded by intermediate-to-mafic veins. The Baocheng batholith has a high radioactive heat generation rate of 2.712–6.843 μW/m3, with an average of 3.846 μW/m3, a radioactive heat-flow value of 30.768 mW/m2 and a heat-flow contribution rate of 38.95%–43.95%. As shown by the results of their thermophysical property analysis, the granites have high thermal conductivity and can serve as high-quality geothermal reservoirs. In combination with previous geological and geophysical data, the geothermal model of the Lingshui area was established in this study. The deep structure indicates the presence of high-conductivity and low-resistivity layers in the basement of the Baocheng batholith. It can be inferred thereby that asthenospheric upwelling may occur and that there exist two magma vents at depth in the batholith. Therefore, magmatic heat at depth and granites with high radioactive heat generation rate serve as the main heat sources in the Lingshui area.

Peyman Afzal, Mohammad Abdideh, Lili Daneshvar Saein

Abstract Identifying geological characteristics such as rock types and fractures is an important step in fractured reservoirs’ modeling and developing oil and gas fields. The productivity index (PI) is an essential parameter for this purpose. There are different methods for separating and identifying rock types and fractures, including simple statistical methods and complex fractal methods based on the spatial structure of the data. In this study, rock areas were isolated after modeling the PI parameter in a rock reservoir in southern Iran by ordinary kriging estimation. Then, the fractal concentration–area (C–A) and concentration–number (C–N) methods were used to classify the PI zones. The C–A fractal analysis revealed six different rock types and zones, and the C–N fractal method indicated four anomalies based on PI data in the studied reservoir rock. Based on the C–N and C–A models, the parts with PI ≤ 44 and PI ≤ 63, respectively, correspond to the production of wells from the reservoir rock matrix in this oil field and PI ≥ 223 include the production of wells at the fracture network of the reservoir rock. Fractal modeling indicates that the highest PI values occurred in the southeast and northwest parts of the studied oil field, suggesting better reservoir rock quality in this area. This problem is attributed to the presence of faults and the accumulation of fractures in these areas, which increases reservoir rock’s PI and permeability. The present study showed that multifractal methods are a very accurate method for separating all types of rock types in the reservoir and it separates things that are not visible in other methods such as petrophysical methods. The anomalies and communities identified for the PI parameter with these methods are well confirmed by geological evidence, especially the impact of fractures, faults and other diagenesis factors in the reservoir rock.

Ao Liu, Jianghai Yang, Jianghai Yang et al.

During the late Paleozoic ice age, tropical coastal depositions have been widely linked to high-frequency sea-level variations, but their linkage with the associated climate change was not fully understood. In the early Permian, two deglaciations occurred in the late Sakmarian and late Artinskian, respectively. During the late Artinskian deglacial warming and transgression, coal-bearing siliciclastic successions of the Liangshan Formation were developed in South China. Three facies associations were recognized from the Liangshan Formation successions in western South China and ascribed to coastal alluvial plain, estuarine, and deltaic environments. Detailed analysis of sedimentology, paleosol morphology, and sandstone petrology suggest a relatively dry-to-wet climate shift and estuarine to deltaic facies transition in the lower Liangshan Formation. This climate shift and facies transition can be temporally correlated based on regional stratigraphic correlations, although precise age constraints are needed to test this correlation. The estuarine interval of the lowest Liangshan Formation signified a rapid transgression during the late Artinskian deglaciation and likely formed during a relatively arid climate with locally small fluvial systems, which provided limited sediment supply. The subsequent transition to and initiation of deltaic deposition was broadly associated with the inferred climate shift and could be primarily resulted from a climate wetting-induced great increase in sediment supply, irrespective of the deglacial sea-level rise.