Igneous Rock Samples Research Articles

Comprehensive multidimensional tectonomagmatic discrimination from log-ratio transformed major and trace elements

An initial geochemical database of a total of 26,058 Pliocene to Holocene fresh igneous rock samples, with assigned tectonic settings from combined geoscientific criteria, was established. A comprehensive discrimination scheme was proposed from linear discriminant analysis (LDA) and canonical analysis of log-ratio transformed compositional data. The multi-normality required for the LDA individually for all tectonic classes was achieved independently for isometric log-ratios (ilr) of major elements and of combined major and trace elements through an online computer program DOMuDAF. The importance of the fulfillment of the multi-normality assumption was documented because it increased the overall percent success from about 0.8% to 6%. The multivariate discordant outlier-free data were used for proposing two multidimensional discrimination models (ilrMd and ilrMTd), respectively, based on discordant outlier-free ilr of only major and of combined major and trace elements. The ilrMTd model always provided significantly higher percent success values (70.6–100%) than the ilrMd model (60.8–96.5%) and, therefore, is recommended to be used when applicable. The ilrMTd model should be preferred over the ilrMd model, in case of controversy. The discrimination of a total of 29 tectonic settings, arranged in 3 Super Groups, 9 Main Groups, 17 Groups, 9 subGroups, and 4 sub-subGroups, was successfully achieved in 19 steps through a total of 60 discriminant function equations, 98 centroids and 98 probability calculations for all classes. The usefulness of the comprehensive multidimensional scheme was demonstrated from 13 application cases. The first two cases were applied to the Pliocene to Holocene rocks from a complex tectonic setting of simultaneously ongoing subduction and rifting in the western part of Mexico. The Tepic-Zacoalco Rift was shown to be like a continental rift, whereas the Colima Rift showed Andean-type continental arc at ridge subduction. This was successfully followed by four application cases of Miocene to Neo-proterozoic ophiolites. Five cases of Neo-archean to Paleo-archean rocks were presented, in which consistent tectonic settings were generally obtained from both models. The next case presented the time-dependent tectonic settings of Tibet from the Lower Jurassic to the Pleistocene, which was possible as 7 subcases. The final case presented as 5 subcases showed time- and space-dependent tectonics for two Archean greenstone belts (Babina and Mauranipur) of the Bundelkhand craton, India. The last two time-dependent tectonic setting applications were possible because of the comprehensive nature of the new 19-step tectonic discrimination procedure. In our final application to the Bundelkhand craton, metamorphic and sedimentary (siliciclastic) rocks provided results consistent with those of the igneous rocks. In one of the earlier Archean terrane applications too (Pilbara craton, Australia), metamorphic rocks gave fully consistent results. Similarly, consistent results were obtained for moderate to highly altered Miocene rocks from the Macquarie Island. Therefore, the new comprehensive discrimination scheme can be recommended for use in all future applications for probability-based inferences on tectonic settings from all kinds of igneous, metamorphic and siliciclastic rocks.

Geochemistry of coal thermally-altered by igneous intrusion: A case study from the Pansan Coal Mine of Huainan Coalfield, Anhui, Eastern China

To investigate the geochemical characteristics of thermally-altered coals formed by igneous intrusion, a series of roof and floor mudstone, thermally-altered coal, and igneous rock samples were collected from a representative borehole profile of the Pansan No. 4-2 coals of the Huainan Coalfield, Anhui Province, Eastern China. Furthermore, seven unaltered coal samples from the same coalbed were collected from seven coal mines of the Huainan Coalfield for comparison. The minerals were analyzed using X-ray diffractometry and optical microscopy. The major element oxides and trace elements were determined by X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), ICP-MS with collision/reaction cell technology, an ion-selective electrode (ISE), and a DMA-80 mercury analyzer. The results indicate that kaolinite and quartz are the dominant minerals in the thermally-altered coals, and pyrite is dominant at the contact zone between the thermally-altered coal and igneous rock. The unaltered Huainan No. 4-2 coals were slightly enriched in only Cr, Se, and W compared to the Chinese coals. However, the thermally-altered coals were slightly enriched in F and V and depleted in Co, Ni, Hg, Sb, Zn, and W compared to the Chinese coals. Although the igneous intrusion reached a thickness of 1.97 m, it had a limited effect on the trace elements of terrigenous origin, i.e., Li, F, Sr, Sn, V, Cr, Co, Ni, Cs, Sc, Ga, Rb, Zr, Nb, Ag, Cd, In, Ba, Hf, Ta, W, Th, U, and rare earth elements and Y (REY). Contact metamorphism resulted the devolatilization and redeposition of coal organic matter, which increased the Be and Ge concentrations of the thermally-altered coals adjacent to the intrusion. Copper, As, Sb, Tl, and Bi were transported by the igneous intrusion and redeposited in the thermally-altered coals. The coals were almost completely stripped of Zn, Se, Mo, Pb, and Hg by the igneous intrusion.

Study and Simulated the Natural Radioactivity (NORM) U-238, Th-232 and K-40 of Igneous and Sedimentary Rocks of Al-Atawilah (Al-Baha) in Saudi Arabia

In this work, gamma-ray spectroscopy based on semiconductor hyper pure germanium (HPGe) detector was used to evaluate the activity concentrations of the natural radionuclides (U-238 (Ra-226), Th-232 and K-40) and the fallout nuclide (Cs-137) for thirty samples of igneous and sedimentary rocks of Al-Atawilah (Al-Baha). The mean values of the activity concentrations of U-238 (Ra-226), Th-232, K-40 and Cs-137 in the igneous samples are found as (11.0, 11.50, 1172.71, 1.47) Bq/Kg respectively. In the sedimentary rocks, the mean values of the activity concentrations of the natural radionuclides (U-238 (Ra-226), Th-232 and K-40) and the fallout nuclide (Cs-137) equal to (12.04, 13.18, 1131.36, 1.60) Bq/Kg respectively. The averages of radiological hazards (Raeq, Hex and Iγ) were calculated and found to be within the UNSCEAR permissible limit values (370 Bq/kg for Raeq, and 1 for Hex and Iγ), except for a slight increase of average value of Iγ in the igneous rock samples (1.36). The results indicate that the dose rate values depend on the kind of rocks (high in some igneous rock samples, and most of sedimentary rock samples have low dose rate). The activities of naturalnuclides were predicted and simulated in T time using a written MATLAB R2020a script based on the average activity concentrations and respective half-lives of U-238 and Th-232 series, and K-40, this is to evaluate the future effects of natural radionuclides on the population and estimate the human inputs in the future.

Apply X-Ray Fluorescence and γ-Ray Spectroscopy to Analyze Igneous and Sedimentary Environmental Samples of Al-Atawilah (Al-Baha), Saudi Arabia

Igneous and sedimentary rocks contain an amount of natural radioactivity (NORM). U-238, Th-232 and their decay products, and K-40 are important sources of gamma-radiation. Knowledge of the radionuclide content of rocks is necessary to estimate the exposure of the population to the radiation. Many types of rocks are used in building and industries, thus the radiation detection is important, it provides a baseline map of levels of the radioactivity in the study region. The purpose of this study is to evaluate the activity concentrations of the natural radionuclides (U-238 (Ra-226), Th-232 and K-40) and the fallout nuclide (Cs-137) (if found) in thirty samples of igneous and sedimentary rocks of Al-Atawilah (Al-Baha). The samples were collected and prepared during 2018/2019, and analyzed with a good experimental instrument (High energy resolution γ-ray spectroscopy with HPGe detector), also these rock samples were analyzed with X-ray fluorescence to subdivided these rocks based on the major oxides proportions contained of each sample. The mean activity concentrations of naturally radionuclides were found in the igneous rock samples varied depending on the type of the igneous rock. For sedimentary rock samples, the activity concentrations were found high for quartz sandstone sample, which may be due to its high proportion of SiO2 and K2O. The estimated mean values of absorbed dose rate are within the permissible limit value. The findings indicate high dose level values in granite (rhyolite) and most of diorite (andesite) igneous rock samples while gabbro (basalt) igneous rock samples (except for one sample) record low levels of dose rate. All sedimentary rock samples have low dose rate (except for the quartz sand-stone sample).

Glimpses of oceanic lithosphere of the Challenger Deep forearc segment in the southernmost Marianas: The 143°E transect, 5800–4200 m

AbstractWe studied nine samples of igneous rocks from the inner wall of the Mariana Trench above the Challenger Deep from 4150 to 6100 m depth recovered by manned submersible and ROV. Samples from two regions that bracket the Moho were studied: (i) 7 samples from a N‐S transect a few km to the west of the Shinkai Seep Field; and (ii) 2 samples from the Shinkai Seep Field. Transect samples include olivine‐2 pyroxene hornblendites, amphibole basalts, basaltic andesite, and hornblende andesite. We analyzed three transect samples for 40Ar/39Ar ages; two yielded good plateau ages of 46.5 ±0.5 Ma (hornblendite) and 46.60 ±0.15 Ma (hornblende andesite). These results combined with previously published results, indicate that this crust formed during an intense 46–47 Ma magmatic episode that occurred 5–6 my after subduction initiation. Hornblendites and hornblende basalts formed from primitive magmas, as shown by high MgO (11–21 wt%), Ni (222–885 ppm) and Cr (412–1145 ppm) contents. Electron microprobe analyses indicate that hornblende is Na‐rich (up to 3.0 wt% Na2O) and that many samples have an atypically large range in plagioclase composition (i.e. individual samples have An < 10 to An 90 plagioclase). Two subgroups can be identified: a mostly deeper depleted suite and a mostly shallower enriched suite. These results indicate that (i) the crust–mantle boundary in this region is transitional, occurring over a ~ 1.5 km interval, with interlayered peridotite and hornblendites between 5800 and 4300 m; and (b) extension to form the Challenger Deep forearc segment occurred by combined stretching of old crust and injection of young basaltic magmas. In contrast to the mostly fresh nature of transect samples, the two samples from the Shinaki Seep Field are intensely altered peridotite and basalt.

THE EFFECT OF GEOLOGICAL PROPERTIES OF DIMENSION STONES ON THE PREDICTION OF SPECIFIC ENERGY (SE) DURING DIAMOND WIRE CUTTING OPERATIONS

Given the increasing demand for dimension stones, mining operations in quarries have always been an important branch of mining engineering. Among different techniques, diamond wire cutting is one of the most common methods of dimension stone mining. A reliable assessment and accurate prediction of diamond wire cutting performance are essential for feasibility analysis and operational planning in this area. This performance depends on factors such as physical, mechanical, and textural properties of the rock and the characteristics of cutting operations which can be evaluated by criteria such as specific energy, production rate, efficiency, and diamond bead wear rate. This study aims to develop a method for predicting the specific energy of diamond wire cutting in dimension stones based on rock properties. For this purpose, the specific energy of diamond wire cutting in 11 different igneous rock samples was measured. Given the high strength and abrasivity of igneous rocks, cutting operations in these rocks generally requires a great amount of energy. In a series of tests performed on the samples, rock properties such as uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Young’s modulus, density, textural properties, abrasivity and operating factors such as pullback amperage were measured. The measured parameters were divided into four groups of physical, mechanical, textural, and operating parameters. After determining the specific cutting energy of each sample, the relationship of the energy with each individual property was investigated. This investigation showed that density, abrasivity, and p-wave velocity respectively had the highest correlation with specific energy. Using the correlation results, four input parameters (one from each of the four considered parameter groups) were selected for inclusion in the prediction model. These parameters were density, abrasivity, wave velocity, and amperage. Multivariate linear regression was then used to analyse the effect of rock properties and operating parameters on specific energy. The developed regression model showed that once the rock properties are known, the specific energy can be predicted with an accuracy of 85.8%. The proposed model can be used to estimate the specific energy of diamond wire cutting operations in dimension stone quarries in advance, and predict the amount of energy consumption, the required energy source, and the optimal cutting machine accordingly.

INVESTIGATING THE ACOUSTIC SIGNS OF DIFFERENT ROCK TYPES BASED ON THE VALUES OF ACOUSTIC SIGNAL RMS

Recent years have seen a vast increase in the use of acoustic waves in real-time and non-destructive detection and monitoring applications in various industries such as mining. Acoustic signal processing methods can provide accurate and reliable estimates of the condition of a process or material in a highly cost-effective way without interrupting the ongoing operations. This paper investigated whether the class of a rock and its strength properties can be estimated based solely on acoustic signals captured during the drilling operation. For this purpose, uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Schmidt rebound number (SRN), and longitudinal wave velocity (Pw) of a series of samples of sedimentary, metamorphic and igneous rocks were measured in a rock mechanics laboratory. The samples were then subjected to a drilling test and the acoustic signal propagating in the drilling medium was recorded by an acoustic sensor. After obtaining the time spectrum of the captured signals, their RMS values were calculated and compared with the mechanical properties of the corresponding rock samples. For the rocks tested in this study, the obtained RMS values were in the range of 800 to 1,600 and generally increased with the increase of strength and hardness. The RMS values obtained for each class of rocks had their own specific range. For sedimentary rocks, this range was 800 to 1000, for metamorphic rocks, it was 1000 to 1200, and for igneous rocks, it was 1400 to 1600. Given the differences in the range of RMS values obtained from the acoustic signals of drilling, these values can be used in the estimation of rock class and strength properties. These results show that there is significant potential for the future use of this approach in the industry for field identification and classification of rocks, especially in deep drilling operations or when there is little information about the characteristics of the rock being drilled.

The effect of mineralogy and textural characteristics on the strength of crystalline igneous rocks using image-based textural quantification

The attempts made to understand and quantify the relationship between rock texture and engineering properties have been accompanied by some ambiguities and uncertainties, and the majority of the approaches, though focusing on particular rock types, have not been so successful for even the same rock types from other regions. This study, therefore, was aimed to investigate the relationship between the texture and strength properties of a wide range of crystalline igneous rocks along with more aspects of textural analysis. For this purpose, fifteen fresh samples of crystalline igneous rocks belonging to the stone quarries of the NW Iran were collected and subjected to compressive and tensile strength tests (UCS and BTS). Thin sections of the samples were used to prepare the full mosaic image layers in three different optical conditions. About 18,000 mineral grains were manually traced on the processed images and the obtained vector data was used for the quantification of various textural parameters including size metrics, shape descriptors, microfabric indices and mineral content. Different phase considerations (full-phasic, monophasic, multiphasic and phase-ratio) were applied to derive the textural characteristics of the individual and multiple minerals and their proportional ratio. Finally, simple linear regression analysis was performed to evaluate the relationship between the texture and strength properties. The results indicated that the newly developed quartz to feldspar size ratio (QFSR) indicator was the only textural parameter that could be significantly correlated with both compressive and tensile strength in a wide range of rock types. The results also highlighted the fact that the role of quartz and feldspar encountered with different rock failure mechanisms could be different; In fact, the tensile strength was obviously affected by the size and content of K-feldspar, while the compressive strength showed a more complicated mechanism and seemed to be controlled by the interference effects of plagioclase and quartz textural properties. Furthermore, the study indicated that the influence of grain size on the rock strength was more important than the grain shape or mineral content.

Remote Raman spectroscopy of natural rocks

We report the remote Raman spectra of natural igneous, metamorphic, and sedimentary rock samples at a standoff distance of 5 m. High-quality remote Raman spectra of unprepared rocks are necessary for accurate and realistic analysis of future Raman measurements on planetary surfaces such as Mars. Our results display the ability of a portable compact remote Raman system (CRRS) to effectively detect and isolate various light- and dark-colored mineral phases in natural rocks. The CRRS easily detected plagioclase and potassium feldspar end members, quartz, and calcite in rocks with high fluorescence backgrounds. Intermediate feldspars and quartz, when found in rocks with complex mineralogies, exhibited band shifts and broadening in the ${504{-}510}\,\,{{\rm cm}^{ - 1}}$504-510cm-1 and ${600{-}1200}\,\,{{\rm cm}^{ - 1}}$600-1200cm-1 regions. A good approximation of intermediate plagioclase feldspars was possible by using overall Raman spectral shape and assigning other minor Raman peaks in addition to the $ 504{-}510\,\,{{\rm cm}^{ - 1}}$504-510cm-1 peaks. Detection of olivine and pyroxene in mafic rocks allowed for compositional characterization.

Petrogenesis and tectonic setting of Late Paleozoic to Late Mesozoic igneous rocks in Cambodia

Emplacement of igneous rocks from the Carboniferous to the Middle Jurassic of Cambodia was controlled by the Indosinian Orogeny, which was related to the sequence of suturing and collision between the continental fragments from Gondwana. To constrain magma genesis, tectonic setting, and relationship with igneous rocks in neighboring countries, we determined the magnetic susceptibility, chemical compositions, Rb-Sr isochron ages and Sr-Nd isotope ratios for igneous rock samples from Cambodia. Igneous rocks in Cambodia can be divided by the inferred Mae Ping fault into magnetite series in the NE region and ilmenite series in the SW region. The igneous rocks in the NE region showed I-type or A-type and metaluminous signatures, and strong involvement of mantle source materials. They are subdivided into older and younger adakitic rocks and non-adakitic rocks. The igneous rocks in the SW region showed non-adakitic and slightly metaluminous to peraluminous signatures. These have significant involvement of source materials with relatively uniform Nd isotope ratios but variable Sr isotope ratios, which may have originated from the lower to middle continental crust. The Late Triassic to Middle Jurassic igneous rocks were formed by the subduction of the Paleo-Tethys Ocean crust associated with the collision of the Sibumasu Terrane with the Indochina Terrane (the Indosinian Orogeny II). The younger granitic rocks showed A-type signature and are regarded as post-orogenic, within the plate or rifting zone that intruded in association with the subduction of the Paleo-Pacific Ocean crust beneath Indochina during the Cretaceous to the Paleogene.

Anisotropy of Magnetic Susceptibility and Preferred Pore Orientation in Lava Flow from the Ijen Volcanic Complex, East Java, Indonesia

Anisotropy of magnetic susceptibility (AMS) has been used in various studies related to interpreting the direction of lava flow, some of which have shown ambiguity with regard to the data generated. In this study, we explored an alternative option to support the aforementioned application, using lava flow type igneous rock samples from the Ijen Volcanic Complex, East Java, Indonesia. We have investigated the preferred rock pore orientations from micro-computed tomography (μCT) images and quantified their directions. We then calculated their correlation with AMS data by calculating the angle between preferred pore orientation. The axis with the smallest gap to the preferred pore orientation of each sample was assumed to imply lava flow direction. Different lava flow direction preferences were obtained from different magnetic ellipsoids. Another important factor for consideration is the relative vertical position of the sampling site within a single lava flow unit. Only one out of five samples (ANY2) show good quantitative conformity between AMS data, preferred pore orientation, and topographical slope, despite these limitations. Our results point to a direction that seems to be correct and coherent on a physical basis. Additional research would likely clarify the issues involved. This encourages us to explore and work further in this field of research.

Precise magnesium isotope analyses of high-K and low-Mg rocks by MC-ICP-MS

This study presents a chemical protocol for the separation of Mg that is particularly adapted for diverse igneous rock samples, especially for high-K and low-Mg rocks.

Comparative Petrographic Analysis of Volcanic Rocks in Five Different Areas Using “R”

Petrographical analysis is a visual method to describe the mineral properties of a rock sample, related to its composition and classification. The mineral composition is mostly determined using a comparator, thus it is merely a quantitative method. This paper uses multivariable statistics as tools to support the visual classification. We took 89 thin sections from five locations, based on secondary data, gathered from five final projects from Department of Geology ITB: Mt. Lamongan-Probolinggo (LAM), Mt. Banyuresmi-Bogor (BAN), Mt. Kromong-Palimanan (KRM), Mt. Sangkur-Garut (SAN), and Mt. Wangi-Purworejo (WAN). The locations is Quaternary volcanic (LAM, KRM, SAN, and WAN) and Tertiary (BAN), consists of 85 igneous rock samples, three pyroclastics, and one sedimentary rock sample. The mineral percentage data was then analyzed using Principal Component Analysis (PCA) and Cluster Analysis (CA) with R. Our data frame size was 89 rows x 24 columns. Our preliminary results show a separation between Quartenary and Tertiary samples on PCA and CA plots. We identified three clusters: cluster 1 BAN; cluster 2 LAM, KRM, SAN, WAN, and BAN, and cluster 3 LAM, KRM, SAN, WAN, and BAN. Based on our PCA plot, cluster 1 shows a strong influence of: chlorite, calcite, and quartz; cluster 2: piroxene, plagioklas, olivine, glass and cluster 3: olivine, piroxene, opaque, glass, and feldspar. Following the results we see that there are samples from BAN detached from the rest. We believe this is due to an anomalous volcanic process on that spot. On the other hand we see the similarity between samples from different locations. Based on those analyses, we perceive that multivariable statistics can support visual petrographic analysis by reading the data structure, selecting stronger variables and extracting clusters.

Determination of ferrous and ferric iron from total iron content and thermogravimetric analysis

Ferrous ( $$\hbox {Fe}^{2+}$$ ) and ferric ( $$\hbox {Fe}^{3+}$$ ) iron content in mineral samples was determined from total iron (as obtained, for instance, from X-ray fluorescence analysis) and mass increase upon switching the purge gas from inert to oxidizing, at high temperature, in a thermogravimetric analysis. The method was validated using analytical-grade ilmenite ( $$\hbox {FeTiO}_{3}$$ , or $$\hbox {Fe}^{2+}\hbox {O}\cdot \hbox {TiO}_{2}$$ ) and magnetite ( $$\hbox {Fe}_{3}\hbox {O}_{4}$$ , or Fe2+ · Fe 2 3+ O3). The estimated mass percentages of FeO are less than the expected values, according to chemical composition, by 1.1 and 1.2 percentage points for ilmenite and magnetite, respectively. The application of this method is further illustrated by determining the $$\hbox {Fe}^{2+}$$ and $$\hbox {Fe}^{3+}$$ content, expressed as FeO and $$\hbox {Fe}_{2}\hbox {O}_{3}$$ , in three samples of igneous rocks.

Estimating the uniaxial compressive strength of rocks with Schmidt rebound hardness by considering the sample size

The Schmidt hammer is commonly used for the prediction of unconfined compressive strength and other mechanical properties of rocks from surface rebound hardness values since it is quick, easy, inexpensive, and non-destructive testing method. In this study, metamorphic, sedimentary, and igneous rock samples were collected from various locations in Turkey to predict the rock strength from Schmidt rebound hardness. Schmidt rebound tests were performed on cubic samples with an edge length of 11 cm and uniaxial compressive strength tests were carried out on cubic samples with an edge length of 5 cm in accordance with ASTM and EN standards and suggested procedure by ISRM. New relationship coefficients between unconfined compressive strength and Schmidt rebound hardness values were suggested according to rock type. Finally, some diagrams were developed to be practically used for estimating the uniaxial compressive strength from Schmidt rebound hardness values by considering the sample size obtained from the experimental work.

Drag pick cutting tests: A comparison between experimental and theoretical results

This paper aims at reporting the results of a number of drag pick cutting tests on selected igneous rock samples to compare the experimentally determined maximum cutting force (FC′) values with theoretically estimated ones. First, a review on theoretical rock cutting models proposed for both chisel and conical picks was presented in detail. Experimental study consists of both chisel and conical pick cutting tests in unrelieved (single-pick) cutting mode with varying cutting depths. FC′ values were determined from experimental results, and theoretical models were utilized to compute FC′ for all cutting conditions. Computed and experimentally determined FC′ data were then compared for a referenced cutting depth. It is shown that the theoretical models might overestimate or underestimate FC′ and cannot give reliable results. Finally, explanations for these mismatches were presented.

In situ measurements of radionuclide concentrations in south of Mugla city, Turkey

The paper presents distribution of radionuclide elements for different samples of igneous, metamorphic and sedimentary rocks in the south of Mugla city, Turkey. The composite image maps for each of radioelement ratios (eU, eTh and K), radiogenic heat-producing map (RHP) and absorbed dose rate of these radionuclides in air were calculated and generated anomaly maps. The obtained results were compared with geological units of the study area. It has been observed that western side of the study area (the Bodrum Peninsula) is mainly characterized volcanic rocks that display high radioactivity concentrations (for U, Th, and K, 120.2 Bq/kg, 101.60 Bq/kg, and 690.1 Bq/kg, respectively). The latite–andesite association causes higher Th concentrations (varying between 1.5 and 101.6 Bq/kg). Higher U and Th anomalies are close relation with the mineral compositions of the volcanic rocks and their silica contents. Due to K-bearing minerals such as K-feldspar (orthoclase, sanidine, biotite) higher K concentrations are determined. On the other hand, metamorphic and sedimentary rocks is dominant in the eastern side of the study area. The sedimentary units have the lowest radioactive concentrations (for U, Th, and K, 8, 0.20, and 24 Bq/kg, respectively), whereas marble and cherty marbles has higher U and K concentrations. It has been also seen that schist and calc-schists exhibit important thorium enrichment (80–100 Bq/kg).

Dynamic Mechanical Behavior of Dry and Water Saturated Igneous Rock with Acoustic Emission Monitoring

The uniaxial cyclic loading tests have been conducted to study the mechanical behavior of dry and water saturated igneous rock with acoustic emission (AE) monitoring. The igneous rock samples are dried, naturally immersed, and boiled to get specimens with different water contents for the testing. The mineral compositions and the microstructures of the dry and water saturated igneous rock are also presented. The dry specimens present higher strength, fewer strains, and rapid increase of AE count subjected to the cyclic loading, which reflects the hard and brittle behavior and strong burst proneness of igneous rock. The water saturated specimens have lower peak strength, more accumulated strains, and increase of AE count during the cyclic loading. The damage of the igneous rocks with different water contents has been identified by the Felicity Ratio Analysis. The cyclic loading and unloading increase the dislocation between the mineral aggregates and the water‐rock interactions further break the adhesion of the clay minerals, which jointly promote the inner damage of the igneous rock. The results suggest that the groundwater can reduce the burst proneness of the igneous rock but increase the potential support failure of the surrounding rock in igneous invading area. In addition, the results inspire the fact that the water injection method is feasible for softening the igneous rock and for preventing the dynamic disasters within the roadways and working faces located in the igneous intrusion area.

Investigating the effect of strength on the LCPC abrasivity of igneous rocks

The abrasivity of rocks results in tool wear in rock excavation or drilling projects. It can affect significantly the cost and schedule of the projects performed in abrasive rock massess. For this reason, the understanding of the mechanism of rock abrasivity is very important for excavation projects. This study investigates the effect of strength on the LCPC abrasivity coefficient (LAC) for igneous rocks. The LCPT test, the uniaxial compressive strength (UCS) and the Brazilian tensile strength (BTS) tests were carried out on the igneous rock samples. The abrasive mineral content (AMC) was also determined for each rock type. First, the LAC was correlated to the AMC and a very good correlation was found between the two parameters. Then, the multiple regression analysis was carried out by including the AMC, UCS and BTS to the analysis in order to infer the effect of the strength on the LAC. It was seen that the correlation coefficients of multiple regression models were greater than that of the relation between the LAC and the AMC. It is concluded that the AMC is the dominant parameter determining the abrasivity of rock. On the other hand, the rock strength has also significant effect on rock abrasivity.

Mesozoic strike-slip movement of the Dunhua–Mishan Fault Zone in NE China: A response to oceanic plate subduction

The NE-striking Dunhua–Mishan Fault Zone (DMFZ) is one of two branches of the continental-scale sinistral Tan–Lu Fault Zone in NE China. The field data presented here indicate that the ca. 1000km long DMFZ records two phases of sinistral faulting. The structures produced by these two phases of faulting include NE–SW-striking ductile shear belts and brittle faults, respectively. Mylonite-hosted microstructures and quartz c-axis fabrics suggest deformation temperatures of 450°C–500°C for the ductile shear belts. Combining new zircon U–Pb dates for 14 igneous rock samples analyzed during this study with the geology of this region indicates these shear belts formed during the earliest Early Cretaceous. This phase of sinistral displacement represents the initial formation of the DMFZ in response to the northward propagation of the Tan–Lu Fault Zone into NE China. A phase of Early Cretaceous rifting was followed by a second phase of sinistral faulting at 102–96Ma, as evidenced by our new U–Pb ages for associated igneous rocks. Combining our new data with the results of previous research indicates that the DFMZ records a four-stage Cretaceous evolutionary history, where initial sinistral faulting at the beginning of the Early Cretaceous gave way to rifting during the rest of the Early Cretaceous. This was followed by a second phase of sinistral faulting at the beginning of the Late Cretaceous and a second phase of local rifting during the rest of the Late Cretaceous. The Cretaceous evolution of the DMFZ records the synchronous tectonic evolution of the NE China continent bordering the Pacific Ocean. Two phases of regional N–S compression generated the two phases of sinistral faulting within the DMFZ, whereas two-stage regional extension generated the two phases of rifting. The two compressive events were the result of the rapid low-angle subduction of the Izanagi and Pacific plates, whereas the two-stage extension was caused by the roll-back of these respective plates. The final closure of the Mongol–Okhotsk Ocean at the beginning of the Early Cretaceous intensified the synchronous compression in NE China, causing the northward propagation of the Tan–Lu Fault Zone.