Thermal evolution behavior of the organic matter and a ray of light on the origin of vitrinite-like maceral in the Mesoproterozoic and Lower Cambrian black shales: Insights from artificial maturation

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F21%3A00544727" target="_blank" >RIV/61389005:_____/21:00544727 - isvavai.cz</a>

Výsledek na webu

<a href="https://doi.org/10.1016/j.coal.2021.103813" target="_blank" >https://doi.org/10.1016/j.coal.2021.103813</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.coal.2021.103813" target="_blank" >10.1016/j.coal.2021.103813</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Thermal evolution behavior of the organic matter and a ray of light on the origin of vitrinite-like maceral in the Mesoproterozoic and Lower Cambrian black shales: Insights from artificial maturation

Popis výsledku v původním jazyce

The overmature Precambrian to Lower Paleozoic marine shales from China contain relatively simple organic matter (OM) composition, which is dominated by in-source solid bitumen (i.e., solid bitumen in the hydrocarbon source rocks). The thermal evolution behavior of the original OM and the determination of thermal maturity in the Precambrian to Cambrian marine shales have been challenging for decades. The vitrinite-like maceral (VLM) is widely present in these marine shales, and its origin is still unknown. To address these issues, the immature Proterozoic Xiamaling shales from China and the immature Cambrian Alum shales from Sweden, and a Chinese immature Carboniferous coal were heat-treated at temperature range of 300 degrees C to 550 degrees C. The carbonized residue of the artificially matured samples was examined for their morphological and reflectance variation, and the results were compared with data on the other overmature natural shales from China and Sweden. OM components are similar in the Xiamaling and Alum immature oil shales, consisting of filamentous algae, matrix bituminite, bituminite, VLM and liptodetrinite, and rare thucholites are present in the Xiamaling shales. The algal-derived OM decomposed gradually due to hydrocarbon generation at 300-350 degrees C. OM is mainly composed of the in-source solid bitumen in the artificially heated shales after 350 degrees C, similar to the overmature Precambrian to Cambrian natural shales, and the in-source solid bitumen gradually loses its mass with increasing thermal maturity. The in-source solid bitumen is derived from the thermal cracking of the retained oil or the direct conversion of algal-derived liptinite macerals (e.g., the bituminite) or their mixture. VLM in the Xiamaling oil shales can not be observed after 350 degrees C, but VLM is still present in the Alum oil shales. It can be inferred that there is a different source of VLM in these shales, and VLM in the Xiamaling oil shales contains more volatile material. The VLM in the Xiamaling shales may be biodegradation products of liptinites under anoxic environments. The origin of VLM in the Cambrian Alum shales requires further study to be verified, although it is certain that graptolites are not its sources. The reflectance of in-source solid bitumen (SBRo) increases with heat-treated temperature in both the Xiamaling shales and the Alum shales, but at different rates, which may be due to the difference of the original kerogen composition in these shales. VLM reflectance (VLMRo) and SBRo in sections perpendicular to bedding can be used to determine the maturation level of the Precambrian-Cambrian sediments. Their relation to equivalent vitrinite reflectance (EqVRo) can be expressed by the following equations: EqVRo = 1.07 x VLMRo - 0.18, EqVRo = 0.87 x SBRo + 0.25 (in the Precambrian sediments) and EqVRo = 1.15 x SBRo + 0.01 (in the Cambrian sediments).

Název v anglickém jazyce

Thermal evolution behavior of the organic matter and a ray of light on the origin of vitrinite-like maceral in the Mesoproterozoic and Lower Cambrian black shales: Insights from artificial maturation

Popis výsledku anglicky

The overmature Precambrian to Lower Paleozoic marine shales from China contain relatively simple organic matter (OM) composition, which is dominated by in-source solid bitumen (i.e., solid bitumen in the hydrocarbon source rocks). The thermal evolution behavior of the original OM and the determination of thermal maturity in the Precambrian to Cambrian marine shales have been challenging for decades. The vitrinite-like maceral (VLM) is widely present in these marine shales, and its origin is still unknown. To address these issues, the immature Proterozoic Xiamaling shales from China and the immature Cambrian Alum shales from Sweden, and a Chinese immature Carboniferous coal were heat-treated at temperature range of 300 degrees C to 550 degrees C. The carbonized residue of the artificially matured samples was examined for their morphological and reflectance variation, and the results were compared with data on the other overmature natural shales from China and Sweden. OM components are similar in the Xiamaling and Alum immature oil shales, consisting of filamentous algae, matrix bituminite, bituminite, VLM and liptodetrinite, and rare thucholites are present in the Xiamaling shales. The algal-derived OM decomposed gradually due to hydrocarbon generation at 300-350 degrees C. OM is mainly composed of the in-source solid bitumen in the artificially heated shales after 350 degrees C, similar to the overmature Precambrian to Cambrian natural shales, and the in-source solid bitumen gradually loses its mass with increasing thermal maturity. The in-source solid bitumen is derived from the thermal cracking of the retained oil or the direct conversion of algal-derived liptinite macerals (e.g., the bituminite) or their mixture. VLM in the Xiamaling oil shales can not be observed after 350 degrees C, but VLM is still present in the Alum oil shales. It can be inferred that there is a different source of VLM in these shales, and VLM in the Xiamaling oil shales contains more volatile material. The VLM in the Xiamaling shales may be biodegradation products of liptinites under anoxic environments. The origin of VLM in the Cambrian Alum shales requires further study to be verified, although it is certain that graptolites are not its sources. The reflectance of in-source solid bitumen (SBRo) increases with heat-treated temperature in both the Xiamaling shales and the Alum shales, but at different rates, which may be due to the difference of the original kerogen composition in these shales. VLM reflectance (VLMRo) and SBRo in sections perpendicular to bedding can be used to determine the maturation level of the Precambrian-Cambrian sediments. Their relation to equivalent vitrinite reflectance (EqVRo) can be expressed by the following equations: EqVRo = 1.07 x VLMRo - 0.18, EqVRo = 0.87 x SBRo + 0.25 (in the Precambrian sediments) and EqVRo = 1.15 x SBRo + 0.01 (in the Cambrian sediments).

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

20701 - Environmental and geological engineering, geotechnics

Projekt

<a href="/cs/project/EF16_019%2F0000728" target="_blank" >EF16_019/0000728: Výzkum ultrastopových izotopů a jejich využití v sociálních a environmentálních vědách urychlovačovou hmotnostní spektrometrií</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

International Journal of Coal Geology

ISSN

0166-5162

e-ISSN

1872-7840

Svazek periodika

244

Číslo periodika v rámci svazku

AUG

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

17

Strana od-do

103813

Kód UT WoS článku

000677973400003

EID výsledku v databázi Scopus

2-s2.0-85108311933