Geochemistry of high-Mg andesites from the early Cretaceous Yixian Formation, western Liaoning: Implications for lower crustal delamination and Sr/Y variations

85 volcanic rocks of the Yixian Formation from the Sihetun type section werecollected and analyzed for geochemical and isotopic compositions. Major element compositionsindicate that the Sihetun volcanic rocks are high magnesium andesites with some basalts occurring atthe bottom of section. The Sihetun high magnesium andesites (SiO_2 = 52.82-59.31 wt%, Al_2O_3=14.15-16.35wt%) show many characteristics of adakites such as depletion in heavy rare-earth elements(HREE; Yb = 1.03-1.88 μg/g) and Y(12-20 μg/g) and high Sr (620-1323 μg/g) and Sr/Y(32-88), withhigh La_N/Yb_N ratio (10-25). They share similar major and trace element characteristics to volcanicrocks from the Xinglonggou Formation except their lower Nd isotope ratios (^(143)Nd/^(144)Nd(130Ma) = 0.5118-0.5119, ε_(Nd) (130Ma) = -11.6-13.8, ^(87)Sr/^(86)Sr (130 Ma) = 0.7058-0.7064.They were interpreted in a way that eclogite that formed at the base of thickened Archean lowercrust of the North China craton foundered into the convecting mantle and subsequently melted andinteracted with peridotite. However, compared to the Xinglonggou volcanic rocks, the source of theSihetun magma contained more ancient continental crustal material in order to explain its evolved Ndisotopes. The age of the Sihetun Formation was 120 to 130 Ma, and this indicates that delaminationlasted to the early Cretaceous period. The Sr contents and Sr/Y ratios of the Sihetun high-Mgandesites show significant negative correlations with SiO_2 for samples with SiO_2 】 56%. Thesesuggest that the Sr and Sr/Y values were reduced due to fractional crystallization of plagioclase.Accordingly, the effect of crystallization on volcanic Sr and Sr/Y ratio has to be taken intoaccount.

Reaction experiments between tonalitic melt and mantle olivine and their implications for genesis of high-Mg andesites within cratons

High-Mg （Mg#〉45） andesites （HMA） within cratons attract great attention from geologists. Their origin remains strongly debated. In order to examine and provide direct evidence for previous assumptions about HMA＇s genesis inferred from petrolog- ical and geochemical investigations, we performed reaction experiments between tonalitic melt and mantle olivine on a six-anvil apparatus at high-temperature of 1250-1400℃ and high-pressure of 2.0-5.0 GPa. Our experiments in this work simulated the interaction between the tonalitic melt derived from partial melting of eclogitized lower crust foundering into the Earth＇s mantle and mantle peridotite. The experimental results show that the reacted melts have very similar variations in chemical compositions to the HMAs within the North China Craton. Therefore, this interaction is probably an important pro- cess to generate the HMAs within crations.

Fluid-rock interaction experiments with andesite at 100℃ for potential carbon storage in geothermal reservoirs

Geothermal energy extraction often results in the release of naturally occurring carbon dioxide(CO_(2))as a byproduct.Research on carbon storage using volcanic rock types other than basalt under both acidic and elevated temperature conditions has been limited so far.Our study uses batch reactor experiments at 100℃ to investigate the dissolution of andesite rock samples obtained from an active geothermal reservoir in Sumatra(Indonesia).The samples are subjected to reactions with neutral-pH fluids and acidic fluids,mimicking the geochemical responses upon reinjection of geothermal fluids,either without or with dissolved acidic gases,respectively.Chemical elemental analysis reveals the release of Ca^(2+)ions into the fluids through the dissolution of feldspar.The overall dissolution rate of the rock samples is 2.4×10^(–11)to 4.2×10^(–11)mol/(m^(2)·s),based on the Si release during the initial 7 h of the experiment.The dissolution rates are about two orders of magnitude lower than those reported for basaltic rocks under similar reaction conditions.This study offers valuable insights into the potential utilization of andesite reservoirs for effective CO_(2) storage via mineralization.

Generation of andesite through partial melting of basaltic metasomatites in the mantle wedge:Insight from quantitative study of Andean andesites

Continental crust in average exhibits a similar composition in both major and trace elements to andesites along active continental margins.For this reason,andesitic magmatism above oceanic subduction zones is considered to have played a key role in the generation of continental crust along convergent plate boundaries.With respect to the origin of andesites themselves,however,there is still a hot debate on how they have acquired their geochemcial compositions.The debate is mainly centralized on the relative contributions of crustal contamination,magma differentiation and source mixing,which reaches an impasse in the past decades.The essential reason for this kind of debates is that these three mechanisms only can account for some of the geochemical observations for andesites,leading to insufficient discrimination among them.Nevertheless,the geochemical features of andesites are primarily controled from early to late by the composition of their source rocks in addition to partial melting and magma differentiation processes.If source mixing and partial melting processes in the early stage of andesite magmatism can account for the first-order geochemical features of andesites,there is no need to invoke the late processes of magma differentiation and crustal contamination for andesite petrogenesis.This is illustrated by quantitative forward modeling of the geochemical data for Quaternary andesites from the Andean arc in South America based on an integrated interpretation of these data.The modeling has run with four steps from early to late:(1)dehydration of the subducting oceanic crust at forearc depths;(2)partial melting of the subducting terrigenous sediment and altered oceanic basalt at subarc depths to produce hydrous felsic melts;(3)the generation of basaltic metasomatites(e.g.,Si-excess pyroxenite)in the mantle wedge through reaction of the mantle wedge peridotite with large amounts of the hydrous felsic melts;(4)the production of andesitic melts by partial melting of the basaltic metasomatites.The results not only testify the hypothesis that the trace element and radiogenic isotope compositions of andesites can be directly produced by the source mixing and mantle melting but also demonstrate that partial melting of the basaltic metasomatites can reproduce the lithochemical composition of andesites.The compositional variations of Andean andesites within a single volcanic zone and among different volcanic zones can be explained by incorporating different amounts of heterogeneous hydrous felsic melts into their mantle sources,followed by different degree of partial melting under different pressures and temperatures.Therefore,the source mixing and partial melting processes at subarc depths can account for the first-order geochemical features of Andean andesites.In this regard,it may be not necessary for andesite petrogenesis to invoke the significant contributions from the processes of magma differentiation and crustal contamination.

Geochronology, geochemistry and Hf isotopes of andesites in the Sandaowanzi gold deposit(Great Xing’an Range, NE China): implications for petrogenesis, tectonic setting,and mineralization

The Sandaowanzi gold deposit is an extremely Au-rich deposit in the Northern Great Hinggan Range in recent years.Zircon U-Pb geochronology,Hf isotope analysis,and the geochemistry of andesites of the Longjiang Formation from the Sandaowanzi gold deposit were used to investigate the origin,magmatic evolution as well as mineralization and tectonic setting of the Early Cretaceous epithermal gold deposits in the northern Great Hinggan Range area.Zircon U-Pb dating reveals an emplacement age of 123.4±0.3 Ma,indicating that the andesites of the Sandaowanzi gold deposit was formed during the Early Cretaceous.The andesites are enriched in light rare earth elements relative to heavy rare earth elements and have weak negative Eu anomalies(δEu=0.76-0.90).The rocks are also enriched in large-ion lithophile elements,such as Rb,Ba,Th,U,and K,and depleted in the high-field-strength elements,such as Nb,Ta,and P.These characteristics are typical of volcanic rocks related to subduction.Igneous zircons from the andesite samples have relatively homogeneous Hf isotope ratios,176Hf/177Hf values of 0.282343-0.282502,εHf(t)values of-12.58 to-6.95,and two-stage model ages(TDM2)of 1743-1431 Ma.The characteristics of the andesites of the Longjiang Formation are consistent with derivation from partial melting of enriched mantle wedge metasomatized by subducted-slab-derived fluids.These rocks formed in an extensional environment associated with the closure of the Mongol-Okhotsk Ocean and subduction of the Paleo-Pacific Plate.Mineralization occurred towards the end of volcanism,and the magmatic activity and mineralization are products of the same geodynamic setting.

利用玻璃渣替代安山岩骨料制备耐热混凝土的试验研究

采用普通硅酸盐水泥、安山岩粗细骨料、粉煤灰、玻璃渣制备了耐热混凝土,研究了不同掺量玻璃渣替代部分粗骨料(0、5%、10%)对耐热混凝土在不同温度热处理(常温25℃,110℃烘干,300℃、500℃、700℃、900℃煅烧)前后对混凝土的尺寸、质量、抗压强度、热导率的影响,评价了混凝土的耐热性能,并分析了混凝土在高温热处理过程中的耐热损伤机理。研究结果表明:随温度从25℃升高至900℃,混凝土逐渐脱水脱碳而失重,密度逐渐降低,热导率也相应减小。混凝土的质量和密度可以用来评价混凝土的导热率。随热处理温度的升高,混凝土先收缩后膨胀,抗压强度则随温度的升高而先增加后减少,在300℃时达到最大值,此时混凝土的收缩变形也最小。玻璃渣取代粗骨料比例越高,混凝土变形越大,失质量越大,导热率越小,混凝土抗压强度越低,但整体差异不大。验证了采用玻璃渣取代部分骨料制备耐热混凝土的可行性。

西秦岭郎木寺组火山岩锆石U-Pb年龄及其构造意义

西秦岭郎木寺地区发育了大量的火山岩,是探讨秦岭造山带印支期岩浆作用的重要窗口。目前,关于郎木寺组火山岩的形成时代尚未有很好的约束。据此,笔者对郎木寺组角闪安山岩开展了详细的LA-ICP-MS锆石U-Pb年代学研究。CL图像显示,郎木寺组角闪安山岩的锆石结构表现出典型的岩浆成因特征。锆石U-Pb定年结果显示,角闪安山岩具略有差异的两组年龄,加权平均年龄分别为(221.8±1.2)Ma和(210.6±2.1)Ma。因此,郎木寺组角闪安山岩的形成时代为晚三叠世。结合前人已有成果,笔者认为郎木寺组火山岩代表了秦岭印支期造山作用重要的岩浆事件产物,形成于同碰撞挤压的构造环境。

渤中凹陷中生界火山岩储层裂隙发育程度实验研究:以安山岩为例

渤海湾盆地中生界火山岩发育广泛,但含油气性横向变化较大,失利井较多,勘探风险大,了解火山岩潜山储层内部裂隙发育程度及规律可为中生界火山岩潜山勘探提供理论依据。本文选取中生界安山岩,开展不同构造环境下岩石微裂隙发育程度实验,分析安山岩在不同应力状态下微裂隙发育规模、频率以及微裂隙空间分布,探讨张性和压性构造应力环境下中生界火山岩微裂隙发育能力及空间展布规律。实验结果表明:安山岩在压性和张性环境下均有微裂隙发育;安山岩在较低的压应力作用下产生大量微裂隙,微裂隙发育规模不随应力增大而升高,其原因可能是安山岩本身含有大量先存构造缝、溶蚀缝和溶蚀孔,受较小的应力后“再活化”产生微裂隙;结合渤中凹陷的构造演化过程,安山岩经历了燕山早期北东向压扭、中期伸展,燕山晚期右旋压扭及喜山期伸展,导致其内部裂隙较为发育,其运储能力提升,具备成为优质储层的基本条件。

深埋安山岩动态力学特性及破碎特征

随着开采深度的增加,岩石力学参数随之发生改变,支护方式也应随之适时调整。为准确掌握基建矿山的岩石动态力学性能,以Jama铜矿的主要围岩安山岩为研究对象,开展了不同加载速度下的常规单轴霍普金森压杆(SHPB)试验,得到了安山岩的动态力学参数及破坏特征,并基于断裂力学理论,构建了考虑应变率的平均块度预测模型,并对冲击破碎后的碎块进行扫描电镜分析。试验结果表明:安山岩的动态压缩应力-应变曲线可分为4个阶段,压密阶段较静态曲线表现不明显。随应变率的提高,动态峰值强度及动态强度因子均呈线性增大趋势,单位体积吸能密度和质量破碎能耗均呈二次多项式规律的增长趋势;随新增比表面积的增大,吸能密度呈线性增大;预测模型理论值与试验值高度吻合;不同冲击速度下试件多以沿晶破坏为主,断口形貌较为复杂,相同放大倍数下随冲击载荷的增加,细观分形维数D_(e)呈线性正相关,可为后期自然崩落法底部结构爆破参数优化及工程应用提供一定的参考。

西藏中部尼雄地区“敌布错组”安山岩夹层的发现及地质意义

因缺乏高精度年代学制约,尼雄地区“敌布错组”形成时代及地层归属存在争议。本次工作通过对“敌布错组”安山岩夹层进行锆石U-Pb测年,获得~120 Ma的加权平均年龄,结合该区“敌布错组”碎屑锆石研究成果,表明其形成于早白垩世中晚期(130~120Ma),与区域上则弄群火山-沉积地层形成时代一致,建议将其新厘定为则弄群。根据安山岩样品的全岩地球化学及锆石原位Hf同位素组成,认为其是壳源长英质岩浆与幔源玄武质岩浆混合的产物,形成于洋壳俯冲的构造环境。通过进一步对拉萨地体中、新生代岩浆作用的时空变换规律的总结分析,本文研究认为该套安山岩形成的动力学机制主要与新特提斯洋北向俯冲相关。

闽北邵武地区玄武安山岩的成因和意义——来自年代学、地球化学及Nd-Hf同位素的约束

东南沿海地区中生代火山岩研究成果颇丰,但有关中侏罗世晚期基性火山岩的报道较少,限制了对该区域中生代构造-岩浆活动及大地构造演化的深入理解。本文对江绍断裂带东南侧邵武地区的中生代火山岩开展了系统的岩石学、锆石U-Pb年代学、锆石Lu-Hf同位素、地球化学和Sm-Nd同位素研究。结果显示:邵武地区玄武安山岩喷发年龄为(161.0±2.0)Ma;同位素地球化学结果显示,这些样品中—晚侏罗世锆石的ε_(Hf)(t)值介于-14.33~-10.41之间,ε_(Nd)(t)值较低(-9.2~-8.4),反映富集Nd同位素的特征;岩石地球化学结果表明,该套火山岩具有高w(Al_(2)O_(3))、w(Na_(2)O)、低w(MgO)、w(TFe_(2)O_(3))等特征,稀土总量较低,稀土配分曲线为右倾型,且具弱的Eu负异常,大离子亲石元素Rb、Ba和K相对富集,高场强元素Nb、Ta、Ti、P等相对亏损。综合岩石学和地球化学研究结果,本文认为邵武玄武安山岩起源于交代岩石圈地幔的部分熔融,并经历一定结晶的分异作用,其大地构造背景总体为板内环境。结合前人对区域构造-岩浆活动的认识,本文认为在中侏罗世晚期,太平洋俯冲板片发生回撤、撕裂,导致幔源岩浆底侵并置换了古老壳源岩石,从而东南沿海地区虽整体处于挤压背景,但仍存在局部拉张环境。

Petrogenesis of Mesozoic High-Mg Diorites in Western Shandong: Evidence from Chronology and Petro-geochemistry

The high-Mg diorites, widely occurring in western Shandong, have important implications in the study of the relationship between the Mesozoic magmatism and the nature of the lithosphere and its thinning period in the eastern North China craton （NCC）. The Tietonggou and Jinling intrusions are typically representatives. LA-ICP-MS zircon U-Pb dating, major and trace element and Sr-Nd isotopic compositions of the Mesozoic intrusive rocks from western Shandong, eastern China, were analyzed. The weighted mean 106^pb/ 238^U ages from LA-ICP-MS zircon U-Pb dating results for early norite-diorite, late pyroxene-diorite from the Tietonggou intrusion and biotite-diorite from the Jinling intrusion are （131.4±4.9） Ma（n=15）, （134. 5±2.3） Ma（n=13）, and （132.8±4. 2） Ma（n=12）, respectively, implying that they were formed in the Early Cretaceous. The weighted mean 207^pb/ 204^Pb ages for round zircons from late pyroxene-diorite in the Tietonggou intrusion is （ 2 513 ± 54） Ma（ n= 8）, suggesting that the basement of the North China craton should exist in the research area. The high-Mg diorites are characterized by enrichment in MgO, Na20, and light rare earth elements （LREE）, and they are poor in heavy rare earth elements （HREE） and high field strength elements （HFSE）, being similar to adakite. The existence of the mantle peridotite xenoliths with a high-Mg feature for these intrusive rocks implies that their primary magma should be derived from the upper mantle. However, Sr-Nd isotopic composi- tions （Is： 0.704 75--0.707 15;ENd （130 Ma） values： --3.95 to -- 13.30）, depletion in HFSE, and the occurrence of Archean inherited zircons suggest that crustal materials could be involved in the derivation of the primary magma. The compositional difference between the diorites from the Tietonggou and Jinling intrusions could be attributed to those of magma sources and degrees of partial melting. The Early Cretaceous high-Mg diorites are considered to have been formed by the mixed melting of the delaminated lithosphere （lithospheric mantle ＋ crust） and asthenosphere, based on their geochemistry, the mantlederived xenoliths, and the Early Mesozoic lithospheric evolutionary history of the eastern North China craton.

Rare Earths, Trace Element Characteristics of High-Mg Volcanic Rocks of Yixian Formation in Sihetun West Liaoning Province and Its Apocalypse

The high-Mg volcanic rocks of the Yixian Formation in the Sihetun area have the obvious characteristics of mantie-derived lava in rare earth, trace element characteristics with high Mg # （62 - 70） and high content of compatible elements. In the meantime, the volcanic rocks also have the obvious characteristics of Crust-source material in rare earth, trace element characteristics with high ∑ REE （ 158.78 × 10^-6 - 359.66 × 10^-6 ）, high （La/Yb） N （ 14.61 - 29.60）, high La/Nb（2.37 - 7.52） and high Ba/Nb （67.58- 205.96）, obvious positive anomaly of Pb and negative anomaly of Nb, Ta in trace element spider-gram. In Sr-Nd-Pb isotope the （^87Sr/^86Sr）i ratio is higher than 0.706 and the εNd（ t ） ratio is from - 3.4 to - 13, both reflect enriched Mantle characteristics. The characteristics above of the volcanic rocks combined with the content of Sr, Ba, Y, Yb and the ratio of Sr/Y show that the volcanic rocks have the property of the Sanukite rocks in Setouchi Japan beside subduction zone, and illuminate that the Sanukite rocks can be formed not only in island-arc near subduction zone but also in intro-plate. The analysis indicates that the high-Mg volcanic rocks in the Sihetun area result from the collective function of mantle-derived lava and crust-source materials. The result illuminates that the West Liaoning region is very special in tectonic geochemical background in Cretaceous in East China, and is an ideal region for us to further study the characteristics of magmatic activity as well as the process of Crust-Mantle interaction in Eastern China.

Swelling characteristics of andesite foundation induced by water immersion and their influence on ballastless track subgrade

To study the mechanical and deformation characteristics of ballastless track subgrade filled with micro-expansion fillers in a water-immersed environment, a physical model of ballastless track subgrade was constructed on a 1:2 scale with expansive andesite fillers. A water immersion test was carried out to model the soaking of the expansive soil foundation caused by rising groundwater. The swelling behaviors of the foundation and their influences upon the mechanics and deformations of the subgrade were analyzed. The lateral swelling pressure of the foundation and the heave of the subgrade obviously increased due to the water immersion, and the values were closely related to the overlying load and lateral restraint. The heave deformation of the double-line ballastless track subgrade showed significant nonuniformity along the lateral direction, causing the track slab to incline with a maximum inclination angle of 1.55×10^-3 deg. The heave of the foundation caused a heave in subgrade, but this transferred heave was significantly attenuated. The attenuation rate of the heave at the midline of the track slab was up to 13.38%. The attenuation characteristic can be fully utilized for the anti-heave deformation measures of railway subgrade in expansive soil areas.

Zircon U-Pb age,geochemical and Nd isotopic data of Middle Jurassic high-Mg dioritic dike in Liaodong Peninsula,NE China

Zircon LA-ICP-MS U-Pb age, geochemical and Nd isotopic data are presented for a newly recognized high-Mg dioritic dike from Haicheng, Liaodong Peninsula, NE China, to constrain its petrogenesis. The zircons from the high-Mg diorite exhibit striped absorption and oscillatory growth zoning in the cathodoluminescence （CL） images, and have high Th/U ratios （0. 05-0.9）, indicating a magma origin. Zircon LA-ICP-MS U-Pb dating indicates that 206pb/238U ages of 12 spots of zircons are between 167 Ma and 178 Ma, yielding a weighted mean 206pb/238U age of 172 ＋ 2 Ma （MSWD =4. 1 ）, which represents the forming age of the high-Mg dioritic dike, i. e. Middle Jurassic. Geochemically, the samples have SiO2 =55.4-60. 6 wt. % , Na20 =2. 2-2.76 wt. % , K20 = 1.32-2. 02 wt. % and （Na2O ＋ K2O） =3.82--4. 47 wt. %, belonging to sub-alkaline series and displaying a calc-alkaline evolutionary trend. They are characterized by high MgO （4. 75-6.85 wt. % ）, Mg# （55-61）, Cr（130-262 ppm）, Ni（63-130 ppm）, Sr（568-857 ppm）, and Ba（484-1 130 ppm） contents, with geochemical features analogous to those of high-Mg adakites. They show variable end （t） values （ - 1.3 to - 3.9） , with a weighted value of - 2. 7, which plot intermediately between the field of the ancient continental crust and the depleted mantle source, indicating that both the lower crust and mantle source are necessary for the generation of the parent magma of the Haicheng high-Mg diorites. The Haicheng high-Mg dioritic dike in the Liaodong Peninsula and the Jurassic magmatism in the eastern North China Craton formed under a continental crustal thickening setting that may be related to subduction of the Paleo-Pacific oceanic plate.

Microscopic pore characteristics of andesite and implication from mineral content:A case study in Huoshiling Formation of Changling fault depression,Songliao Basin

In order to study the microscopic pore characteristics of andesite reservoir and the effect of mineral content on the andesite pore,this study takes the andesite of the Huoshiling Formation in Longfengshan of Changling fault depression,Songliao Basin as a subject.The andesite reservoir space was discerned through the observation of cores and casting thin sections.Besides,the pore size distribution of andesites and their mineral contents were quantitatively characterized by high-pressure mercury injection,nitrogen adsorption and XRD,respectively.The results show that:(1)There are various types of reservoir space in andesites,including vesicles,amygdule,intergranular pores,matrix dissolution pores and dissolution pores of amygdala,and three types of fractures including dissolution,structural and explosion fractures.(2)The pore size distribution of andesite is complex.The main pore size of andesite is mid-pore(10-20 nm)with some large-pores(>50 nm).Mid-pore and large-pore provide the main specific surface area,which are the main space for gas storage.(3)The andesite reservoir space in the study area is mainly controlled by dissolution,as supported by the relationship between the change of mineral content and porosity evolution.The porosity of andesites decreases with the increase of quartz and chlorite content,but increases with the increase of soluble mineral,e.g.,feldspar content.

Discovery and Geological Significance of Early Carboniferous High-Mg Diorite in the Balikun Area, Eastern Tianshan

The granodiorites,monzogranites and diorites are widely developed in the Balikun area of Eastern Tianshan Orogen.Of which,LA–ICP–MS zircon U-Pb isotopic dating from the diorites revealed that they were emplaced at 327~333 Ma,representing an important period of magmatism in the Early Carboniferous.Geochemically,they are characterized by moderate SiO2(51.33–62.48 wt%),high but variable MgO(2.04–11.16 wt%,average 5.35),higher Mg#(40–73)and TiO2(0.67–1.29 wt%),Na2O/K2O(1.39–2.95)as well as variable Cr(2.49–675 ppm)and Ni(1.31–174 ppm),showing a geochemistry similar to those of high-Mg diorites or sanukitoids.In addition,they are enriched in the LILE,poor HFSE with an evident negative Nb anomalies and a REE pattern of moderate fractionator between LREE and HREE without or weak negative Eu anomalies.TheirεHf(t)are positive(+3.63–+15.65),suggesting a source from the depleted mantle.In addition,they have high TiO2 and Pb,and large quantity of amphibolite and biotite,indicating that they were most likely derived from the partial melting of depleted mantle metasomatized by the slabderived melt under a hydrous condition.Consequently,combined with the contemporary volcanics and granitoids formed in the island arc settings,we proposed that the subduction was continued till Early Carboniferous in the Bogda-Harlik tectonic belt.After that,wide occurrence of the post-collisional A-type granites and mafic-ultramafic intrusions indicate this tectonic belt entered the post-collisional environment from Late Carboniferous to Permian.

Geochemistry and Geochronology of the High-Mg Gabbro Dykes from Quanji Massif: Implications for the Amalgamation of Tarim Block in NW China and Assembly of the Rodinia Supercontinent

The Tarim Craton is one of the major continental blocks in China.Mafic dykes,ultra-mafic–mafic–carbonatite complex and ultra-mafic–mafic pluton of 0.82–0.75 Ga widely occur in Kuluktage,Aksu and Tieklik area along

Petrogenesis and Tectonic Significance of An Early Paleoproterozoic High-Mg Boninite-Norite-Diorite Suite of Rocks from the Bastar Craton, Central India

Mafic/ultramafic rocks derived from high siliceous(high-Si)high magnesium(high-Mg)mantle melts are an important feature observed during early Precambrian.They provide much important geological and petrological

Strength Developing in Clay-Andesite Brick

The objective of this work was to develop a more and better understanding of the strength developing in clay-andesite fired brick. The purpose was to improve the quality of the clay bricks that are handmade in the southern region of Ecuador to make them suitable for more widespread use in the local construction industry. To achieve our goal, we first physically, chemically, and mechanically characterized the “clayey” and “sandy” materials used in the fabrication of handmade bricks in the region. Second, the optimal mixture (OM): the optimal proportion between the amounts of “clayey” and “sandy” material was sought. Third, clay bricks were prepared using the OM, baked at 950°C, and characterized. In addition, bricks produced by regional artisans were characterized, and the results were compared with the results obtained for the bricks prepared using the OM. Our data reveal that the optimal mixture is 50% “clayey” material and 50% “sandy” material and that with this mixture, an average improvement in brick quality of 300% can be achieved;thus, the use of the OM makes it possible to expand the use of these bricks in the local construction industry and enables an environmentally friendly production process by reducing the intensive exploitation of regional clay deposits. This improvement is achieved by virtue of the anorthite enrichment that occurs in the solid solution, which results from the evolution of andesine. The anorthite contributes to the formation of a stronger matrix among the different grains of the material. Conditions are favorable for this enrichment process to occur when “sandy” materials with high contents of andesite, which is common in Ecuadorian soils, are used.