Cretaceous ongonites (topaz-bearing albite-rich microleucogranites) from Ongon Khairkhan, Central Mongolia: Products of extreme magmatic fractionation and pervasive metasomatic fluid: rock interaction

Lithos ◽  
2015 ◽  
Vol 236-237 ◽  
pp. 173-189 ◽  
Author(s):  
Jaroslav Dostal ◽  
Daniel J. Kontak ◽  
Ochir Gerel ◽  
J. Gregory Shellnutt ◽  
Mostafa Fayek
Keyword(s):  
Rock Interaction ◽  
Central Mongolia ◽  
Metasomatic Fluid

scholarly journals New orogenic type gold occurrences in the Uyanga ore knot (Central Mongolia)

2019 ◽  
Vol 98 ◽  
pp. 08020
Author(s):  
Ariunbileg Sodov ◽  
Olga Gaskova ◽  
Altansukh Gankhuyag ◽  
Dagva-Ochir Lkhagvasuren ◽  
Otgonbaatar Dorjsuren ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Gold Deposits ◽  
Gold Content ◽  
Rock Interaction ◽  
Central Mongolia ◽  
Quartz Veins ◽  
Central Asian ◽  
Mineral Assemblages ◽  
Metallogenic Zone ◽  
Water Rock Interaction

The Khangay-Khentey belt is located in central Mongolia (Central Asian Orogenic Belt). The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentary Erdenetsogt formation. The new Burgetei, Ult and Senjit gold occurrences were studied. The rocks of the Erdenetsogt formation have an irregular gold content: 0.96 g/t Au is determined in quartz vein (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hgand Sb content up to 8.5 ppm and 39 ppm respectively. The Au content of arsenic pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). The ore-mineral assemblages in the new gold occurrences reflect the differences between three explored sites, formed in the course of fluid evolution during the water-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact.

scholarly journals New orogenic type gold occurrences in the Uyanga ore knot (Central Mongolia)

2018 ◽  
pp. 22-36
Author(s):  
Ariunbileg Sodov ◽  
Olga Gaskova ◽  
Altansukh Gankhuyag ◽  
Dagva-Ochir Lkhagvasuren ◽  
Otgonbaatar Dorjsuren ◽  
...  
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Gold Deposits ◽  
Gold Content ◽  
Rock Interaction ◽  
Central Mongolia ◽  
Quartz Veins ◽  
Mineral Assemblages ◽  
Metallogenic Zone ◽  
Host Rocks

The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentary Erdenetsogt formation. About 40 samples were collected from the host rocks, veins and quartz veins in the Uyanga ore knot district in 2016. The new Burgetei, Ult and Senjit gold occurrences were studied. The quartz-sulfide, gold-arsenic and gold-antimony-mercury mineralization are determined in the berecitization, silicification, limonitization and glauconization altered metasomatic zones within the Uyanga ore knot districts. The rocks of the Erdenetsogt formation have an irregular gold content: 0.96 g/t Au is determined in quartz vein taken from trench of the Burgetei occurrence (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hg content up to 851 ppm. This year no sulfide minerals were found in the siltstone of this occurrence. The Au content of arsenical pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). Therefore, the ore-mineral assemblages in the gold occurrences reflect the differences between the three explored sites, formed in the course of fluid evolution during the fluid-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact. The geodynamic position, the type of the hydrothermal alteration of both igneous and sedimentary rocks, textures and mineral assemblages, the mineralization sequences are consistent with orogenic classification for the Burgetei, Ult and Senjit gold occurrences.

NEOPROTEROZOIC TECTONIC EVOLUTION OF THE OPHIOLITIC BAYANKHONGOR SUTURE ZONE, CENTRAL ASIAN OROGENIC BELT (CENTRAL MONGOLIA)

2019 ◽  
Author(s):  
James R. Worthington ◽  
◽  
Claire E. Bucholz ◽  
Uyanga Bold ◽  
Francis A. Macdonald ◽  
...  
Keyword(s):  
Tectonic Evolution ◽  
Suture Zone ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Central Mongolia ◽  
Central Asian

87SR/86SR, δ18O AND NOBLE GASES AS TRACERS OF WATER-ROCK INTERACTION IN THE THEISTAREYKIR GEOTHERMAL FIELD

2020 ◽  
Author(s):  
Marie Haut-Labourdette ◽  
◽  
Daniele Pinti ◽  
André Poirier ◽  
Marion Saby ◽  
...  
Keyword(s):  
Noble Gases ◽  
Geothermal Field ◽  
Rock Interaction ◽  
Water Rock Interaction

Magnetite texture and trace-element geochemistry fingerprint of pulsed mineralization in the Xinqiao Cu-Fe-Au deposit, Eastern China

2020 ◽  
Vol 105 (11) ◽  
pp. 1712-1723
Author(s):  
Yu Zhang ◽  
Pete Hollings ◽  
Yongjun Shao ◽  
Dengfeng Li ◽  
Huayong Chen ◽  
...  
Keyword(s):  
Trace Element ◽  
Triple Junction ◽  
Eastern China ◽  
Black Shales ◽  
Hydrothermal Fluids ◽  
Oscillatory Zoning ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Rock Interaction ◽  
Multiple Pulses

Abstract The origin of stratabound deposits in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China, is the subject of considerable debate. The Xinqiao Cu-Fe-Au deposit in the Tongling ore district is a typical stratabound ore body characterized by multi-stage magnetite. A total of six generations of magnetite have been identified. Mt1 is commonly replaced by porous Mt2, and both are commonly trapped in the core of Mt3, which is characterized by both core-rim textures and oscillatory zoning. Porous Mt4 commonly truncates the oscillatory zoning of Mt3, and Mt5 is characterized by 120° triple junction texture. Mt1 to Mt5 are commonly replaced by pyrite that coexists with quartz, whereas Mt6, with a fine-grained foliated and needle-like texture, commonly cuts the early pyrite as veins and is replaced by pyrite that coexists with calcite. The geochemistry of the magnetite suggests that they are hydrothermal in origin. The microporosity of Mt2 and Mt4 magnetite, their sharp contacts with Mt1 and Mt3, and lower trace-element contents (e.g., Si, Ca, Mg, and Ti) than Mt1 and Mt3 suggest that they formed via coupled dissolution and reprecipitation of the precursor Mt1 and Mt3 magnetite, respectively. This was likely caused by high-salinity fluids derived from intensive water-rock interaction between the magmatic-hydrothermal fluids associated with the Jitou stock and Late Permian metalliferous black shales. The 120° triple junction texture of Mt5 suggests it is the result of fluid-assisted recrystallization, whereas Mt6 formed by replacement of hematite as a result of fracturing. The geochemistry of the magnetite suggests that the temperature increased from Mt2 to Mt3 and implies that there were multiple pulses of fluids from a magmatic-hydrothermal system. Therefore, we propose that the Xinqiao stratiform mineralization was genetically associated with multiple influxes of magmatic hydrothermal fluids derived from the Early Cretaceous Jitou stock. This study demonstrates that detailed texture examination and in situ trace-elements analysis under robust geological and petrographic frameworks can effectively constrain the mineralization processes and ore genesis.

scholarly journals Fluid inclusions in buried quartz of the Yanchang sandstone in the Jiyuan area, Ordos Basin, China: Implications for basin evolution and petroleum accumulation

2020 ◽  
pp. 014459872097451
Author(s):  
Wenqi Jiang ◽  
Yunlong Zhang ◽  
Li Jiang
Keyword(s):  
Fluid Inclusions ◽  
Ordos Basin ◽  
Homogenization Temperature ◽  
Burial Depth ◽  
Hydrocarbon Generation ◽  
Rock Interaction ◽  
Yanchang Formation ◽  
Reflection Data ◽  
And Migration ◽  
Vitrinite Reflection

A fluid inclusion petrographic and microthermometric study was performed on the sandstones gathered from the Yanchang Formation, Jiyuan area of the Ordos Basin. Four types of fluid inclusions in quartz can be recognized based on the location they entrapped. The petrographic characteristics indicate that fluid inclusions in quartz overgrowth and quartz fissuring-I were trapped earlier than that in quartz fissuring-IIa and fissuring-IIb. The homogenization temperature values of the earlier fluid inclusions aggregate around 80 to 90°C; exclusively, it is slightly higher in Chang 6 member, which approaches 95°C. The later fluid inclusions demonstrate high homogenization temperatures, which range from 100 to 115°C, and the temperatures are slightly higher in Chang 9 member. The calculated salinities show differences between each member, including their regression characteristics with burial depth. Combining with the vitrinite reflection data, the sequence and parameters of fluid inclusions indicate that the thermal history of the Yanchang formation mostly relied on burial. Salinity changes were associated with fluid-rock interaction or fluid interruption. Hydrocarbon contained fluid inclusions imply that hydrocarbon generation and migration occurred in the Early Cretaceous. The occurrence of late fluid inclusions implied that quartz cement is a reservoir porosity-loose factor.

scholarly journals A Novel Damage Model for Strata Layers and Coal Mass

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1928 ◽  
Author(s):  
Faham Tahmasebinia ◽  
Chengguo Zhang ◽  
Ismet Canbulat ◽  
Samad Sepasgozar ◽  
Serkan Saydam
Keyword(s):  
Constitutive Model ◽  
Strain Energy ◽  
Damage Model ◽  
Rock Joint ◽  
Coal Mass ◽  
Stored Energy ◽  
Rock Interaction ◽  
Geological Factors ◽  
Coal Rock ◽  
Joint Quality

Coal burst occurrences are affected by a range of mining and geological factors. Excessive slipping between the strata layers may release a considerable amount of strain energy, which can be destructive. A competent strata is also more vulnerable to riveting a large amount of strain energy. If the stored energy in the rigid roof reaches a certain level, it will be released suddenly which can create a serious dynamic reaction leading to coal burst incidents. In this paper, a new damage model based on the modified thermomechanical continuum constitutive model in coal mass and the contact layers between the rock and coal mass is proposed. The original continuum constitutive model was initially developed for the cemented granular materials. The application of the modified continuum constitutive model is the key aspect to understand the momentum energy between the coal–rock interactions. The transformed energy between the coal mass and different strata layers will be analytically demonstrated as a function of the rock/joint quality interaction conditions. The failure and post failure in the coal mass and coal–rock joint interaction will be classified by the coal mass crushing, coal–rock interaction damage and fragment reorganisation. The outcomes of this paper will help to forecast the possibility of the coal burst occurrence based on the interaction between the coal mass and the strata layers in a coal mine.

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