Part 1 of 10
Introduction to the Ophiolitic Belts
INTRODUCTION
The aim of this book is to provide an overview of the ophiolitic processes associated with the Motagua Suture Zone in Guatemala and to show their mineral potential. It includes the final version of the Field Trip to Guatemala designed by the Author.
In preparing this book I have compiled information from different sources, including several internet sources, combined with my personal experiences in the mapping of the area and help and cooperation of the geologists from the Guatemalan Ministry of Energy and Mines.
The Caribbean Plate (Fig. 1) is the result of the Mesozoic-Present interaction of the Nazca, Cocos, North, and South American plates. The margins of these plates are represented by large deformed belts which resulted from several compressional episodes that started in the Cretaceous and were followed by tensional and strike-slip tectonics.
The present-day north-western margin of the Caribbean Plate crops out in Guatemala along the Motagua Suture Zone (MSZ). This zone links the Meso-American trench with the Cayman Islands extensional system as shown in Fig. 2.
The MSZ represents a sinistral shear-zone between the Maya Continental Block (MCB) to the north and the Chortis Continental Block (ChCB) to the south. The MSZ includes the Motagua Fault Systems of Polochic, Motagua, Cabañas, and Jocotán. All these are E-W and ENE-WSW strike-slip faults. Some of them are still seismically active. The MSZ also includes E-W uplift structures (Sierra de Chuacús, Sierra de Las Minas, and Montañas del Mico), pull-apart basins like the one responsible for the formation of the Lake Izabal, and N-S oriented grabens (Chiquimula, Guatemala, etc.).
A presentation I did for my son's 2nd grade class in very basic geological terms and concepts. I brought in numerous fossils I have collected over the years for a visual and interactive teaching aids. I concluded the talk with a mock science experiment displaying the chemical reaction of a volcano erupting.
Definition, metamorphism.
limits and type of metamorphic agents.
Metamorphic processes.
Types of Metamorphism
Classification of metamorphic rocks and textures of metamorphic rocks
Mineral assemblages and Metamorphic grade and facies of metamorphic rocks.
Graphic representation of metamorphic mineral parageneses.
metamorphic rocks and their distinguishing features-megascopic and microscopic study of gneiss, schist, quartzite, marble and slate
Properties and characteristics and uses of metamorphic rocks
Metamorphic Rocks ( Definition - Classification - Common Rocks ) Muhammad Mamdouh
presented for Dr | Magdy Basta
Faculty of petroleum and mining engineering, Suez University
Physical Geology Course ( 2016 - 2017 )
presented by : G7 - Members
GRAPHIC QUARTZ-FELDSPAR INTERGROWTHS IN PEGMATITES: DIFFUSION AND GROWTH KINETICS MIGIF-HAFAFIT AREA, SOUTH EASTERN DESERT EGYPT
During the formation of pegmatites in the Migif-Hafafit area, conditions of crystallization were such that widespread graphic quartz-feldspar intergrowths were formed. The quartz is interpreted to have nucleated epinastically on rough edges and corners of alkali feldspar crystals. The existence of rugose inner feldspar-quartz boundaries and euhedral outer boundaries evidence that the graphic texture is a primary magmatic feature. Rapid growth, at or near volatile-saturated conditions, resulted in quartz saturation along the irregular melt-feldspar inner interface. Slow diffusion of Si and Al species (network formers) in the boundary-layer melt was likely the rate-controlling step for quartz saturation, which occurred along corners and edges, where the feldspar grew most rapidly. Diffusion-limited growth resulted in SiO2 buildup at the interface, producing oscillations from quartz-oversaturated to quartz-undersaturated conditions and thus the rhythmic quartz-feldspar intergrowths. The transition from planar, to edge, to cellular growth, and changes in the lobate inner feldspar-quartz boundary occurred in response to changes caused by crystallization that affect rates of Si-Al diffusion. Evidence of saturation in a volatile phase in these pegmatites indicates that water was a catalyst for feldspar growth and that lower activities of H2O in the melt decrease Si diffusivity at the crystal interface.
The Wadi Sikait Complex:
A Fertile- Post-Collisionl Granite-Pegmatite Suite, Eastern Desert, Egypt.
The Pan-African, Wadi Sikait Complex (WSC), in the south Eastern Desert of Egypt, is a late-tectonic, subsolvus strongly peraluminous, S-type, post-collisionl granite in the Sikait area that features an unambiguous genetic linkage with a proximal, zoned cluster of Be-, REE- and Nb-Ta bearing pegmatites (Abu Rusheid and Nugrus-Sikait area). The WSC is an arcuate belt of orthogneisses, migmatites and other high-grade metamorphic rocks, which mark the boundary between the central Eastern and the south Eastern Deserts of Egypt. The WSC consists of seven internal units (WSC-1 to -3 and PL-1 to -4) that range from chemically primitive biotite, garnet and sillimanite granites (WSC-1 and –2) to a highly evolved, tourmaline- and muscovite- bearing pegmatite granite facies (PL-1 to –4) locally containing endogenous emerald/beryl, molybdinite and cassiterite. Salient petrochemical attributes include A/CNK molar which varies from 1.15 to 1.75, a wide range of SiO2 (68.7-76.9%), high Al2O3 (14.1-16.0%), low CaO (<2.35%) and FeOt+MgO+TiO2 (0.36-6.62%), and with increasing fractionation, enrichment of Na2O, K2O, B, F, Be, Rb, Ga and Li, and depletion of Ba, Sr, Zr, REE and LREE. Strong fractionation is also revealed by Al/Ga (1370-6789), Ba/Rb (<0.01-12), Ca/Sr (21-201), K/Ba (19-9545), Mg/Li (4.26-1421), Na2O/K2O (0.21-34), (Ce/Yb)CN (0.89-83.25), and Eu/Eu* (<0.05-2.29). REE distribution patterns of rare-element pegmatites are lower in REE contents and flatter with prominent negative Eu anomaly than those of the related granites. The REE concentration and the (Ce/Yb)CN ratio decrease from the WSC-1 and -2 through PL-1 and -2 (fine-grained leucogranite) and PL-3 (pegmatitic leucogranite) to the PL-4 (potassic pegmatites).
Genesis of the strongly peraluminous, S-type granite and the associated rare-element pegmatite in the Sikait-Nugrus area is explained by a complex interplay of petrogenetic processes. Rare-elements and boron were previously concentrated in (wackes and mudstone) pelitic sediments deposited in large basins. These rocks underwent step-wise rock dehydration reactions involving muscovite and biotite, under fluid-absent conditions, and successively released these elements to anatectic melt. Rare-elements and volatiles were progressively concentrated via crystal-melt fractionation, the Harker trends of which were obscured by two stages of extraction of residual melt and by episodic, subsolidus redistribution via base-cation leaching. The late magmatic history of the WSC is marked by widespread exsolution of a volatile-rich phase, dispersion of a rare-element- F-B-Be-rich fluid along shear zones and ensuing emigration of rare-element-rich melt-fluid systems upward from the cupola, which led to the regionally zoned Sikait-Nugrus area
A FIELD TRIP THROUGH CENTRAL GUATEMALA
The NW corner of the Caribbean Plate is complicated by the presence of a continental type block, the Chortis Block, within a mostly oceanic plate and a combination of a slip-strike boundary to the north running from the Belize-Guatemala border with a subduction zone to the west where the Cocos Plate is subducted beneath the Caribbean Plate, and an extinguished subduction zones to the north and south, were the Caribbean Plate was temporarily subducted beneath the Maya and Chortis Block.
The Author believes that the migration of the Chortis block in an S-SW and then N direction was one of the mechanisms responsible for the changes observed among the ophiolitic complexes in Guatemala. The Author introduces the idea of the pre-existence of a trench associated with the Motagua-Jalomáx slip-strike fault system near the north border of Honduras, currently filled up and destroyed by the northward migration of the Chortis Block. Also, he introduces the idea of an orogenic event - The Chuacús Orogeny - probably the same age as the Laramide Orogeny in North America. The Author postulate that the Chuacús Orogeny pushed younger ophiolites complexes in Guatemala to the surface and is responsible for the metamorphic basin of Central Guatemala - The Chuacús Series. The obduction of the oldest ophiolites on the western end of the belts may have being caused by the passing by of the Jamaica block on its way to its present position south of Cuba.
A presentation I did for my son's 2nd grade class in very basic geological terms and concepts. I brought in numerous fossils I have collected over the years for a visual and interactive teaching aids. I concluded the talk with a mock science experiment displaying the chemical reaction of a volcano erupting.
Definition, metamorphism.
limits and type of metamorphic agents.
Metamorphic processes.
Types of Metamorphism
Classification of metamorphic rocks and textures of metamorphic rocks
Mineral assemblages and Metamorphic grade and facies of metamorphic rocks.
Graphic representation of metamorphic mineral parageneses.
metamorphic rocks and their distinguishing features-megascopic and microscopic study of gneiss, schist, quartzite, marble and slate
Properties and characteristics and uses of metamorphic rocks
Metamorphic Rocks ( Definition - Classification - Common Rocks ) Muhammad Mamdouh
presented for Dr | Magdy Basta
Faculty of petroleum and mining engineering, Suez University
Physical Geology Course ( 2016 - 2017 )
presented by : G7 - Members
GRAPHIC QUARTZ-FELDSPAR INTERGROWTHS IN PEGMATITES: DIFFUSION AND GROWTH KINETICS MIGIF-HAFAFIT AREA, SOUTH EASTERN DESERT EGYPT
During the formation of pegmatites in the Migif-Hafafit area, conditions of crystallization were such that widespread graphic quartz-feldspar intergrowths were formed. The quartz is interpreted to have nucleated epinastically on rough edges and corners of alkali feldspar crystals. The existence of rugose inner feldspar-quartz boundaries and euhedral outer boundaries evidence that the graphic texture is a primary magmatic feature. Rapid growth, at or near volatile-saturated conditions, resulted in quartz saturation along the irregular melt-feldspar inner interface. Slow diffusion of Si and Al species (network formers) in the boundary-layer melt was likely the rate-controlling step for quartz saturation, which occurred along corners and edges, where the feldspar grew most rapidly. Diffusion-limited growth resulted in SiO2 buildup at the interface, producing oscillations from quartz-oversaturated to quartz-undersaturated conditions and thus the rhythmic quartz-feldspar intergrowths. The transition from planar, to edge, to cellular growth, and changes in the lobate inner feldspar-quartz boundary occurred in response to changes caused by crystallization that affect rates of Si-Al diffusion. Evidence of saturation in a volatile phase in these pegmatites indicates that water was a catalyst for feldspar growth and that lower activities of H2O in the melt decrease Si diffusivity at the crystal interface.
The Wadi Sikait Complex:
A Fertile- Post-Collisionl Granite-Pegmatite Suite, Eastern Desert, Egypt.
The Pan-African, Wadi Sikait Complex (WSC), in the south Eastern Desert of Egypt, is a late-tectonic, subsolvus strongly peraluminous, S-type, post-collisionl granite in the Sikait area that features an unambiguous genetic linkage with a proximal, zoned cluster of Be-, REE- and Nb-Ta bearing pegmatites (Abu Rusheid and Nugrus-Sikait area). The WSC is an arcuate belt of orthogneisses, migmatites and other high-grade metamorphic rocks, which mark the boundary between the central Eastern and the south Eastern Deserts of Egypt. The WSC consists of seven internal units (WSC-1 to -3 and PL-1 to -4) that range from chemically primitive biotite, garnet and sillimanite granites (WSC-1 and –2) to a highly evolved, tourmaline- and muscovite- bearing pegmatite granite facies (PL-1 to –4) locally containing endogenous emerald/beryl, molybdinite and cassiterite. Salient petrochemical attributes include A/CNK molar which varies from 1.15 to 1.75, a wide range of SiO2 (68.7-76.9%), high Al2O3 (14.1-16.0%), low CaO (<2.35%) and FeOt+MgO+TiO2 (0.36-6.62%), and with increasing fractionation, enrichment of Na2O, K2O, B, F, Be, Rb, Ga and Li, and depletion of Ba, Sr, Zr, REE and LREE. Strong fractionation is also revealed by Al/Ga (1370-6789), Ba/Rb (<0.01-12), Ca/Sr (21-201), K/Ba (19-9545), Mg/Li (4.26-1421), Na2O/K2O (0.21-34), (Ce/Yb)CN (0.89-83.25), and Eu/Eu* (<0.05-2.29). REE distribution patterns of rare-element pegmatites are lower in REE contents and flatter with prominent negative Eu anomaly than those of the related granites. The REE concentration and the (Ce/Yb)CN ratio decrease from the WSC-1 and -2 through PL-1 and -2 (fine-grained leucogranite) and PL-3 (pegmatitic leucogranite) to the PL-4 (potassic pegmatites).
Genesis of the strongly peraluminous, S-type granite and the associated rare-element pegmatite in the Sikait-Nugrus area is explained by a complex interplay of petrogenetic processes. Rare-elements and boron were previously concentrated in (wackes and mudstone) pelitic sediments deposited in large basins. These rocks underwent step-wise rock dehydration reactions involving muscovite and biotite, under fluid-absent conditions, and successively released these elements to anatectic melt. Rare-elements and volatiles were progressively concentrated via crystal-melt fractionation, the Harker trends of which were obscured by two stages of extraction of residual melt and by episodic, subsolidus redistribution via base-cation leaching. The late magmatic history of the WSC is marked by widespread exsolution of a volatile-rich phase, dispersion of a rare-element- F-B-Be-rich fluid along shear zones and ensuing emigration of rare-element-rich melt-fluid systems upward from the cupola, which led to the regionally zoned Sikait-Nugrus area
A FIELD TRIP THROUGH CENTRAL GUATEMALA
The NW corner of the Caribbean Plate is complicated by the presence of a continental type block, the Chortis Block, within a mostly oceanic plate and a combination of a slip-strike boundary to the north running from the Belize-Guatemala border with a subduction zone to the west where the Cocos Plate is subducted beneath the Caribbean Plate, and an extinguished subduction zones to the north and south, were the Caribbean Plate was temporarily subducted beneath the Maya and Chortis Block.
The Author believes that the migration of the Chortis block in an S-SW and then N direction was one of the mechanisms responsible for the changes observed among the ophiolitic complexes in Guatemala. The Author introduces the idea of the pre-existence of a trench associated with the Motagua-Jalomáx slip-strike fault system near the north border of Honduras, currently filled up and destroyed by the northward migration of the Chortis Block. Also, he introduces the idea of an orogenic event - The Chuacús Orogeny - probably the same age as the Laramide Orogeny in North America. The Author postulate that the Chuacús Orogeny pushed younger ophiolites complexes in Guatemala to the surface and is responsible for the metamorphic basin of Central Guatemala - The Chuacús Series. The obduction of the oldest ophiolites on the western end of the belts may have being caused by the passing by of the Jamaica block on its way to its present position south of Cuba.
The name ophiolite derived from Greek root which means
Ophio : snake or serpent Litho : Stone
The green colour, structure and texture of sheared ultramafic rocks is similar to some serpents
Economically :
Massive Sulphide
It founded within pillow lava most of massive Sulphide associated in ophiolites have well developed Gossans (bright colored iron oxide, hydroxides, and sulfides) which is very rich in gold.
Chromite
Stratiform (be tabular or pencil shape) or podiform (irregular shape) within ultra-mafic rocks
These deposits are developed on serpentinite peridotite
Laterites (nickel and iron)
Asbestos
Talc
Magenesite
ophiolite sequence :
Sediments
Pillow Lavas
Dykes
Gabbros
Layered Gabbro
Layered Peridotite
Upper mantle
Similar to Geological and Geochemical Evolution of Guatemala's Ophiolitic Belts and their Mineral Potential. Part 1 of 10. (20)
Valls Geoconsultant (VG) is offering a quality assurance program for the field sampling procedures which include collection, labeling, and shipping components. VG also has established a series of procedures for logging and general mapping. This is especially important in larger projects, where more than one geologist is doing field descriptions. Part II of this series will deal in more details with the correct procedures of other type of exploration work.
VG has thus implemented a procedure for the field naming of rocks that follows the model: ALTERATION / (QUALIFIER & NAME) / TEXTURE / MINERALIZATION. A system for the codification of the alteration and mineralization type and intensity is also incorporated in these procedures.
For sequential samplings like pitting or drilling, we should take field duplicate samples every 40 samples when exploring for gold, or every 20 when exploring for other metals. We should use blanks every 33 samples, samples for external controls every 100 samples and standard samples with each batch of samples send for processing at 50 samples intervals. We should codify the sampling booklets to show the type of control for the sample.
A summary of several presentations organized by the PGO, the TSX, and others about the basics of the NI 43-101, orientations on how to write a technical report, when to write it, who can write it, and common errors.
How to use Kudos to advertise your work.
Accelerating Research Impact
Join a global community of researchers using Kudos to communicate work more effectively and accelerate its positive impact in the world.
Introducción al tema del NI 43-101. Esto es parte de un programa de conferencias organizadas entre P. Geo. M. Sc. Ricardo Valls de Valls Geoconsultant y el Dr. Rafael Rodriguez de la Facultad de Minas de la Universidad Nacional de Medellín para cumplimentar la formación de los estudiantes de geología del último año.
NICKEL LATERITE DEPOSITS
Geology and Lineament Analysis of the Baja Verapaz Ophiolitic Complex
Summary
The Baja Verapaz Ophiolitic Complex encompasses an ophiolitic complex protruding metamorphic rocks from the Chuacús Series in Central Guatemala. The targeted mineralization is represented by two types of Nickel-Cobalt laterite deposits, an in situ type and an alluvial-deluvial type. A typical laterite profile consists of a Limonitic Horizon which is separated from the Saprolite Horizon by a transition zone named the Mottled Zone. The Saprolite Horizon lays over the Saprock that transitions into the Bedrock, usually represented by serpentinized olivine-rich Lherzolites or Dunites. The usual thickness of these deposits averages 33 meters, but there are known intersections of more than 90 meters in the area.
Nickel content varies from 0.4% in the Limonite Horizon to over 1.5% at the bottom of the Saprolite Horizon. Higher values are sometime found associated to the presence of Garnierite.
Cobalt values vary from 0.08 to 0.2%. There is also the presence of traces of Au and PGM, usually associated to the Mottled Zone.
The lineament analysis completed over an area of 1,541.22 km2 encompassing the whole Baja Verapaz ophiolitic complex, was aimed to identify other potential zones of laterite development in this area. The lineament analysis was completed using a combination of topographic maps in electronic format, aero photos and a D.E.M. of the region and included an aeromagnetic survey of the area. The study also included image interpretation of satellite images and 3D strain and stress analysis.
The study indicated the existence of new potential targets and clarified the relationship between the known deposits.
THE PADRE ANTONIO COPPER PROJECT
The Padre Antonio Project is located in western Guatemala, specifically, east of the village of Santa Eulalia in the Huehuetenango Department. The property has an area of 24 km2 in rugged terrain, which range in elevation between 2,000 and 2,500 meters (AMSL).
The Padre Antonio Project was discovered by an Italian immigrant turned prospector after he organized a stream sediment sampling of the Tziquiná river that crosses the area. Near the highest copper value samples, located almost at the centre of the license,
Mr. Bruno Montuori then organized the digging of a 7 meters pit that found massive chalcopyrite and abundant secondary copper minerals.
The gold potential of Guatemala
Most of the work reflected in this section is based on a geochemical and geological survey conducted by the Korean International Cooperation Agency (KOICA) and the Korean Institute of Geology, Mining, and Materials (KIGAM) in 1998. The main objective of the Korean surveys was to fulfill the geochemical exploration for discriminating the characteristics of mineralization of the Motagua Basin and its vicinities.
The author also used the data from previous exploration studies (mainly pitting and assay results) conducted by Transmetales Ltda. (Transmetales), Cominco Resources International Limited (Cominco), and other companies.
The ore deposits in the east and east central Guatemala are generally divided into three types of deposits:
Vein type of gold-silver and lead-zinc deposits widely distributed in volcanic and granite intrusives especially in the southern part of Motagua fault zone;
Nickel-chromium deposits associated with ultramafic serpentinite and peridotite rocks in the middle part of Guatemala; and
Antimony and polymetallic ore deposits related with Tertiary rock which is exposed in the regions of mid-Tertiary volcanic activity.
For the most part they form pods or narrow veins, which appear to be widely scattered throughout the dissected volcanic plateau. From the Paleozoic to the Quaternary, tectonic and magmatic activity has occurred in different occasions which have caused a diversity of ore deposits.
The present section compiles the existing information on the Izabal District and the La Unión Area, south of the Izabal Lake. It shows the gold potential of several targets in the region.
Having a geochemical or geophysical anomaly is not enough. You NEED to have a space for your deposit. This will help you concentrate your exploration efforts on places where there is the possibility of a deposit. This method will help you concentrate your exploration on the most prospective targets, thus increasing your productivity.
Having a geochemical or geophysical anomaly is not enough. You NEED to have a space for your deposit. This will help you concentrate your exploration efforts on places where there is the possibility of a deposit. This method will help you concentrate your exploration on the most prospective targets, thus increasing your productivity.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
PRESENTATION ABOUT PRINCIPLE OF COSMATIC EVALUATION
Geological and Geochemical Evolution of Guatemala's Ophiolitic Belts and their Mineral Potential. Part 1 of 10.
1.
2. INTRODUCTION
The aim of this book is to provide an overview of the ophiolitic processes associated with the
Motagua Suture Zone in Guatemala and to show their mineral potential. It includes the final
version of the Field Trip to Guatemala designed by the Author.
In preparing this book I have compiled information from different sources, including several internet
sources, combined with my personal experiences in the mapping of the area and help and cooperation of
the geologists from the Guatemalan Ministry of Energy and Mines.
The Caribbean Plate (Fig. 1) is the result of the Mesozoic-Present interaction of the Nazca, Cocos, North,
and South American plates. The margins of these plates are represented by large deformed belts which
resulted from several compressional episodes that started in the Cretaceous and were followed by
tensional and strike-slip tectonics.
The present-day north-western margin of the Caribbean Plate crops out in Guatemala along the Motagua
Suture Zone (MSZ). This zone links the Meso-American trench with the Cayman Islands extensional system
as shown in Fig. 2.
The MSZ represents a sinistral shear-zone between the Maya Continental Block (MCB) to the north and
the Chortis Continental Block (ChCB) to the south. The MSZ includes the Motagua Fault Systems of
Polochic, Motagua, Cabañas, and Jocotán. All these are E-W and ENE-WSW strike-slip faults. Some of them
are still seismically active. The MSZ also includes E-W uplift structures (Sierra de Chuacús, Sierra de Las
Minas, and Montañas del Mico), pull-apart basins like the one responsible for the formation of the Lake
Izabal, and N-S oriented grabens (Chiquimula, Guatemala, etc.).
3. Figure 1. Structural sketch map of the Caribbean area (from Giunta et al., 2002).
Figure 2. Bathometric representation of the Caribbean Plate and its relationship with the neighboring plates
and structures.
4. OPHIOLITIC BELTS IN GUATEMALA
An ophiolite is a thrust sheet of ancient oceanic lithosphere obducted over the continental crust in the
course of orogeny. Most geologists interpret these sequences as oceanic crustal and upper mantle
material that has been pushed up onto continents when slivers of the sea floor were caught between
converging plates (Fig. 3). The term "ophiolite" comes from the Greek word "snake stone".
Figure 3. Diagram showing the model of formation of an ophiolitic belt.
An ophiolite is a stratified igneous rock complex composed of upper basalt member, middle gabbro
member, and lower peridotite member. Some large complexes measure over 10 km thick, 100 km
wide, and 500 km long. Basalt and gabbro are commonly altered into patchy green rocks, and
peridotite is mostly changed into black, greasy serpentinite.
The ophiolite succession can be correlated with the seismologic layering of the oceanic lithosphere
(Fig. 4). The sedimentary cover corresponds to Layer 1, basaltic pillow lava matches Layer 2,
sheeted dikes and gabbro with occasional plagiogranite intrusions are correlated to Layer 3, and
ultramafic cumulates and residual mantle peridotite represent Layer 4 (mantle).
5. Figure 4. Typical ophiolitic succession.
Ophiolites usually occur as a nappe (intact thrust sheet) or as a mélange (tectonic mixture of
fragments). In collisional orogenic belts, ophiolites generally lie on older continental basement,
while in circum-Pacific orogenic belts ophiolites generally lie on younger accretionary complexes.
In Guatemala, they occur as mélanges over older rocks (Fig. 5).
Following is a list of the most common minerals related to the ophiolitic processes. The list is by
no means exhaustive and serves only to explain the principal constituents of the ultramafic rocks
which maybe involved in the process of serpentinization or may be present as accessory minerals.
Albite NaAlSi3O4
Anorthite CaAl2Si2O4
Augite (Ca, Mg, Fe, Al) 2(Al, Si) 2O6
Awaruite Ni3Fe
Bastite Mg2Si2O6
Brucite Mg(OH)2
Chromite FeCr2O4
Clinopyroxene Ca(Mg, Fe)Si2O6
Diopside (Ca, Mg) Si2O6
Fayalite FeSiO4
8. Petrologic Classifications of Ophiolites
Ophiolites may have formed either at divergent plate boundaries (mid-oceanic ridges) or at
convergent plate boundaries (supra-subduction zones; i.e. island arcs and marginal basins). They
are called MOR and SSZ types, respectively. These types are identified by chemical composition
of the rocks and minerals in comparison with those from various tectonic settings on the earth at
present.
Ophiolitic mantle peridotite is the refractory residue after extraction of basaltic melt through partial
melting processes in the mantle. Although primary mantle peridotite may be lherzolite with
abundant clinopyroxene, it changes into clinopyroxene-poor (or -free) harzburgite as the degree of
melting increases (Fig. 6). The mantle peridotite samples dredged from the mid-oceanic ridges are
mostly lherzolite, while those dredged from supra-subduction zones (trench walls) are mostly
harzburgite.
Figure 6. Modal variation of residual mantle peridotite with increasing degree of melting.
In Guatemala, only the South and North Motagua ophiolitic belts are classified as harzburgites (trench
wall), while the rest are layered intrusives alternating olivine-rich lherzolites; normal lherzolites and
websterites more typical of an Island Arc environment.
Ophiolitic igneous cumulates show systematic variation in the crystallization sequence of minerals
corresponding to the petrologic diversity of the underlying peridotite mantle. The mineral
crystallizing next to olivine typically varies from plagioclase through clinopyroxene to
9. orthopyroxene as the degree of melting in the underlying mantle increases (Fig. 6). The
characteristic cumulate rocks correspondingly vary from wehrlite to harzburgite.
In general, ophiolitic basalt also varies from alkali basalt or high-alumina basalt (like mid-ocean
ridge basalt (MORB)) through low-alumina basalt (like island-arc tholeiite (IAT)) to boninite
(high-magnesia andesite) in correspondence with the petrologic variation of the underlying
members (Fig. 7).
Figure 7. Systematic variations of the ophiolitic igneous cumulates.
The Guatemalan ophiolitic belts are characterized by extreme petrologic diversity. Juxtaposition of olivine-
depleted websterites and olivine-rich Lherzolites is common for the youngest belts.
10. Ophiolitic Phases
The following petrologic assemblages are usually associated with an ophiolitic profile (Fig. 8).
Figure 8. Representation of the ocean crust. The seismic structure (from seismic experiments) is combined
with the lithology of ophiolites.
The Pillow Basalt Layer (PBL) is well represented in some ophiolitic belts in Guatemala, while it
is absent (or have not yet been found) in others. The best example of the PLB can be found
associated to the Huehuetenango ophiolitic belt (Fig. 9). Pseudo pillow lavas can be also found
associated to the North Motagua ophiolitic belt (Fig. 10).
11. Figure 9. Outcrop of pillow basalts of the Huehuetenango ophiolitic belt.
Figure 10. Pseudo pillow lavas from the North Motagua ophiolitic belt.
According to the established models (Fig. 11), we can find VMS type of deposits associated to the
PBL. The Sierra de Santa Cruz ophiolitic belt hosts such type of deposit, the Cyprus type copper
deposit of Oxec.
12. Figure 11. Schematic ophiolitic complex.
The Sheeted Dike Layer (SDL) is best represented again at the Huehuetenango ophiolitic belt (Fig.
12). The unit consists of 100% dikes with no intervening screens of other rocks. Possibly related
to the underlying gabbros, they are not derived directly form them.
Figure 12. The sheeted dike layer of the Huehuetenango ophiolitic belt.
The Cumulate Gabbro Layers (CGL) are generally mafic at the base and grade upward to more
feldspathic rocks. Olivine becomes progressively more iron-rich, reaching Fo70 in the uppermost
13. gabbros. Orthopyroxene is present but far less abundant than in the underlying deformed ultrmafic
rocks. Diopside augite is the principal pyroxene. Toward the top of the layered gabbros, irregular
intrusive bodies of plagiogranites occur. These are thought to be the final differentiation product
of the gabbroic magma, which gave rise to layered rocks. In Guatemala we have found cumulate
gabbros only near the River Cahabón within the Sierra de Santa Cruz ophiolitic belt.
The Ultramafic Cumulate Layers (UCL) are usually located below the lowest layered mafic, the
transition to the harzburgitic mantle section, and are usually marked by the occurrence of
plastically deformed dunites. The deformation, which is characteristic of the underlying
harzburgite, dies out in this transition zone. In terms of mineral composition, the mafic-ultramafic
transition is smoothed by the presence of ultramafic layers, gabbro dikes, sills and impregnations
in the dunites and the uppermost harzburgites. The amount of clinopyroxene and plagioclase
increase upward through the zone. Thus, dunite (olv) at the base passes up through wherlite
(olv+cpx) to clinopyroxenite and troctolite (plag+olv). With the decrease in the amount of olivine,
then, the degree of deformation decreases.
The Metamorphic Envelope (ME). These are dynamometamorphic rocks welded to the base of
ophiolites (metamorphic soles or dynamothermal aureoles). They are generally believed to have
formed during detachment and/or emplacement of oceanic lithosphere into orogenic belts. The
rocks found here range from mylonitic peridotites to garnet amphibolites, epidote amphibolites,
and greenschists. In Guatemala we find greenschist facies associated to all ophiolitic belts (Figs.
13-14), garnet amphibolites associated to the North Motagua ophiolitic belt (Fig 15), and the best
example of mylonitization can be found at the Juan de Paz – Los Mariscos ophiolitic belt (Fig. 16).
14. Figure 13. Greenschist facies at Huehuetenango
ophiolitic belt.
Figure 14. Greenschist facies of the South
Motagua ophiolitic belt.
15. Figure 15. Garnet amphibolites associated with
the North Motagua ophiolitic belt.
Figure 16. Zone of intense mylonitization at the
Juan de Paz - Los Mariscos ophiolitic belt.
Ophiolitic Ages
Reported formation ages of ophiolites show three distinct peaks at about 750, 450 and 150 Ma,
respectively (Fig. 17). These are called ophiolite pulses. Each pulse corresponds to the period of
worldwide magmatic event as represented by voluminous granite intrusions. Production rate of
oceanic crust was distinctly high during the 80 and 120 Ma interval of Cretaceous time, as
evidenced by wide area of the ocean floor formed in this interval. This interval corresponds to the
later half of the Mesozoic ophiolite pulse.
Figure 17. Ophiolitic "pulses" in Earth's history.