scholarly journals Filling Provenance in Fracture Cavity Formation within Aksu Area, Tarim Basin, NW China: Indicators from Major and Trace Element, Carbon-Oxygen, and Strontium Isotope Compositions

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Qiqiang Ren ◽  
Jianwei Feng ◽  
Ji Ma ◽  
He Du
Keyword(s):  
Trace Element ◽  
Tarim Basin ◽  
Hydrothermal Fluid ◽  
Sedimentary Environment ◽  
Wall Rock ◽  
Strontium Isotope ◽  
Carbon And Oxygen Isotopes ◽  
Himalayan Orogeny ◽  
Full Analysis ◽  
Compositional Patterns

Abstract With an aim to increase the understanding about sedimentary environment and isotopic and chemical characteristics of fillings in fracture cavities with multiple compositions, we conducted scanning electron microscope (SEM), fluid inclusion testing (FIT), common and trace element chemistry, full analysis testing, isotopic compositions (δ13C, δ18O, 87Sr/86Sr), and apatite fission track testing to study the formation environment of Aksu area, Tarim Basin. According to outfield and microscope observations, combined with SEM results, three textural and compositional type fractures and cavities were distinguished. Through fine analysis of geochemistry characteristics on fractures, cavities, multiple filling periods, and environments were interpreted. Constrained by rare earth element (REE) pattern diagram, relationships between carbon and oxygen isotopes, strontium isotope, the compositional patterns, and generation environment of the fracture and cavities were determined. The results show that (1) cavity, fracture filling, and wall rock primarily consist of calcite, with a proportion of 56.85%, 80.48%, and 81.00%, respectively. (2) Four fracture sets have been distinguished in the Ordovician limestone of the karst cave, Middle-Late Caledonian (Set 1), Early Hercynian (Set 2), Indo-Yanshanian (Set 3), and Himalayan orogeny (Set 4). Two stages of cave filling deposition are distinguished. Stage I was coeval with the Middle-Late Caledonian Set 1 fractures and is attributable to the circulation of freshwater fluid. Stage II was coeval with the Early Hercynian Set 2 fractures and is attributable to deep hydrothermal fluid circulation. (3) Cavity, fracture filling, and wall rock in Ordovician strata are slightly influenced by diagenesis alteration and territorial supply. Three significant filling stages were distinguished, freshwater fluid with strong oxidizing environment (Middle-Late Caledonian), hydrothermal fluid with authigenic abnormal enrichment (indicating obvious hypoxic sedimentary water, Early Hercynian), and high-temperature hydrothermal fluid from deep earth (primarily influenced by magmatism, Indo-Yanshanian, and Himalayan).

scholarly journals Differentiating between Inherited and Autocrystic Zircon in Granitoids

2020 ◽  
Vol 61 (8) ◽  
Author(s):  
Hugo K H Olierook ◽  
Christopher L Kirkland ◽  
Kristoffer Szilas ◽  
Julie A Hollis ◽  
Nicholas J Gardiner ◽  
...  
Keyword(s):  
Trace Element ◽  
Source Region ◽  
Wall Rock ◽  
Magma Source ◽  
Trace Element Data ◽  
Element Data ◽  
Age Constraints ◽  
Erroneous Interpretation ◽  
Zircon Fraction

Abstract Inherited zircon, crystals that did not form in situ from their host magma but were incorporated from either the source region or assimilated from the wall-rock, is common but can be difficult to identify. Age, chemical and/or textural dissimilarity to the youngest zircon fraction are the primary mechanisms of distinguishing such grains. However, in Zr-undersaturated magmas, the entire zircon population may be inherited and, if not identifiable via textural constraints, can lead to erroneous interpretation of magmatic crystallization age and magma source. Here, we present detailed field mapping of cross-cutting relationships, whole-rock geochemistry and zircon textural, U–Pb and trace element data for trondhjemite, granodiorite and granite from two localities in a complex Archean gneiss terrane in SW Greenland, which reveal cryptic zircon inheritance. Zircon textural, U–Pb and trace element data demonstrate that, in both localities, trondhjemite is the oldest rock (3011 ± 5 Ma, 2σ), which is intruded by granodiorite (2978 ± 4 Ma, 2σ). However, granite intrusions, constrained by cross-cutting relationships as the youngest component, contain only inherited zircon derived from trondhjemite and granodiorite based on ages and trace element concentrations. Without age constraints on the older two lithologies, it would be tempting to consider the youngest zircon fraction as recording crystallization of the granite but this would be erroneous. Furthermore, whole-rock geochemistry indicates that the granite contains only 6 µg g–1 Zr, extremely low for a granitoid with ∼77 wt% SiO2. Such low Zr concentration explains the lack of autocrystic zircon in the granite. We expand on a differentiation tool that uses Th/U ratios in zircon versus that in the whole-rock to aid in the identification of inherited zircon. This work emphasizes the need for field observations, geochemistry, grain characterization, and precise geochronology to accurately determine igneous crystallization ages and differentiate between inherited and autocrystic zircon.

Comparative geochemistry of pelites from the Moinian and Appin Group (Dalradian) of Scotland

1981 ◽  
Vol 118 (5) ◽  
pp. 477-490 ◽  
Author(s):  
R. St. J. Lambert ◽  
J. A. Winchester ◽  
J. G. Holland
Keyword(s):  
Trace Element ◽  
Sedimentary Environment ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Central Highlands ◽  
The Individual

SummaryPelitic schists from the Appin Group of the Dalradian Supergroup are all chemically distinct from pelitic schists in the older Moinian Supergroup. In addition, trace-element geochemistry can also discriminate between the individual pelitic schists within the Appin Group, especially those within the Lochaber Subgroup. These differences apparently relate mainly to differences in provenance rather than differences of sedimentary environment, and are sufficiently consistent to offer a means for correlation or identification of pelitic units in areas of the Central Highlands where the stratigraphy is still in dispute.

Carbon isotope (δ13Ccarb) stratigraphy of the Early–Middle Ordovician (Tremadocian–Darriwilian) carbonate platform in the Tarim Basin, NW China: implications for global correlations

2020 ◽  
pp. 1-22 ◽  
Author(s):  
Xiaoqun Yang ◽  
Zhong Li ◽  
Tailiang Fan ◽  
Zhiqian Gao ◽  
Shuai Tang
Keyword(s):  
Sea Level ◽  
Carbon Isotope ◽  
Tarim Basin ◽  
Large Scale ◽  
Carbonate Platform ◽  
Sedimentary Environment ◽  
Isotopic Analysis ◽  
Nw China ◽  
Middle Ordovician ◽  
Positive Shift

Abstract Guided by conodont biostratigraphy and unconformities observed in the field, stable carbon isotopic analysis (δ13Ccarb) was performed on 210 samples from Lower–Middle Ordovician (Tremadocian to Darriwilian) sections and wells in the Tarim Basin, NW China. The δ13C trend in the Tarim Basin sections has three distinct characteristics: (1) from the Tremadocian to the Floian, a positive shift from −1.9 ‰ to −0.2 ‰ is observed near the boundary between the Penglaiba Formation and the Yingshan Formation; (2) from the Floian to the Dapingian, a positive shift in δ13C from −3 ‰ to −0.7 ‰ occurred under large-scale sea-level rise and a change in the sedimentary environment from a restricted platform to an open platform. Changes in the conodont type are also observed in the Tabei region; and (3) from the Dapingian to the Darriwilian, δ13C first decreased and then increased, showing a negative shift at the Dapingian–Darriwilian boundary. During the Floian, δ13C decreased in the study area, while it first decreased and then increased in other regions, which may reflect local sea-level movements in response to isostatic crustal movements. Two types of positive shift were identified at the Floian–Dapingian boundary, which likely show the effects of local factors, including a disconformity, dolomitization, and platform restriction, superimposed on the global signal of the carbon isotope. Some conodont zonations and recurrent negative excursions in Tremadocian, Floian and Dapingian stages appear to be truncated by unconformities, which are accompanied by short-term subaerial exposure due to sea-level fall and local tectonic uplift.

Late Yanshan-Himalayan hydrocarbon reservoir adjustment and hydrothermal fluid activity in the central Tarim Basin

2007 ◽  
Vol 52 (S1) ◽  
pp. 244-252 ◽  
Author(s):  
XingYang Zhang ◽  
ShuiChang Zhang ◽  
Ping Luo ◽  
RuKai Zhu ◽  
Zhong Luo ◽  
...  
Keyword(s):  
Tarim Basin ◽  
Hydrothermal Fluid ◽  
Hydrocarbon Reservoir

scholarly journals Hydrothermal Dissolution of Deeply Buried Cambrian Dolomite Rocks and Porosity Generation: Integrated with Geological Studies and Reactive Transport Modeling in the Tarim Basin, China

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Wenwen Wei ◽  
Daizhao Chen ◽  
Hairuo Qing ◽  
Yixiong Qian
Keyword(s):  
Tarim Basin ◽  
Carbonate Rocks ◽  
Reactive Transport ◽  
Wall Rock ◽  
Transport Modeling ◽  
Reactive Transport Modeling ◽  
Fluid Temperature ◽  
Upward Migration ◽  
Vertical Permeability ◽  
Northern Tarim Basin

The burial dissolution of carbonate rocks has long been an interesting topic of reservoir geologists. Integrated with geological studies and reactive transport modeling, this study investigated the Cambrian dolomites that were buried at depths up to 8408 m and still preserved a large amount of unfilled dissolution vugs from the borehole TS1 in the northern Tarim Basin. Studies indicate that these vugs were formed in association with fault-channeled hydrothermal fluids from greater depth through “retrograde dissolution” as the fluid temperature dropped during upward migration. The reactive transport modeling results suggest an important control of the vertical permeability of wall-rock on fluid and temperature patterns which, in turn, would control the spatial distribution of dissolving-originated porosity. The hydrothermal dissolution mainly occurred in dolomite wall-rocks with higher vertical permeability (extensive development of tensional fractures and connected pore spaces), producing additional dissolved porosity there during deep burial. This study implicates the importance of multidisciplinary approaches for understanding the burial/hydrothermal dissolution of dolomite rocks and predicting favourable deep/ultradeep carbonate reservoirs.

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