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7.8: Luster - Geosciences

7.8: Luster - Geosciences


Overview

Luster refers to the appearance of the reflection of light from a mineral’s surface. Minerals with a metallic luster have the color of metal, like silver, gold, copper, or brass (Figure 7.14). While minerals with a metallic luster are often shiny, not all shiny minerals are metallic. Make sure you look for the color of metal, rather than for just a shine. Minerals with non-metallic luster do not appear like metals. They may be vitreous (glassy), earthy (dull), waxy (similar to a candle’s luster), greasy (oily), or other types (Figure 7.15).


Geology in the Laboratory

This lab book was created for teachers and students of an introductory geology class for non-science majors at the college level. Many of these labs are traditional exercises that have been reworked over the years to be more suitable for students without a lot of math and science in their academic background. The learning outcomes of these labs are quite similar to those of a traditional lab manual, however the presentation of terms and methodologies are more straight forward and down to Earth.

Chapter 1 Math and Science Review
1.1 Introduction
Procedure
Exercises
1.2 Using a Ruler to Make Measurements
Introduction
The Lab
Let’s Review Metric Measuring
Let’s Review Measuring in the American System
Using Your Knowledge . Let’s Actually Measure Something.
Summary & Review
1.3 Determining the Size of a Molecule
. Let’s Get Small .
Objective
The Concept
Necessary Background Information
Materials Needed
Procedure: Part I
Procedure: Part II
Calculations
Determining the Size of a Molecule

Chapter 2 Minerals, The Building Blocks of Rocks Identifying Minerals in the Laboratory
2.1 Identifying Minerals
Purpose
Preparation
Materials
Procedure
Introduction
Physical Properties of Minerals
Luster
Color
Hardness
Streak
Transparency
Crystal Form
Fracture and Cleavage
Specific Gravity
How to Identify a Mineral Specimen
Classifying Minerals into the 6 Major Mineral Groups
The mineral groups (& their signature compound) that we use in this class
2.2 Building Minerals from Elements
Introduction
Materials Needed
Procedure
Notes on Reading a Chemical Equation
2.3 Building a Tetrahedron
Introduction
Materials Needed
Procedure
Summary
2.4 Turning Minerals into Igneous Rocks
Introduction
Materials Needed
Procedure

Chapter 3 Rocks, the Earth’s Building Blocks
Classification of Rock
Purpose
Preparation
Materials Needed
Procedure
Introduction
The Three Types of Rocks
Using an Identification Key to Classify Rocks
3.1 Identifying Igneous Rocks
Introduction
Textures of Igneous Rocks
Composition of Igneous Rocks
Procedure
3.2 Identifying Sedimentary Rocks
Introduction
Procedure
A Few Things to Keep in Mind During Lab
3.3 Identifying Metamorphic Rocks
Introduction
Procedure

Chapter 4 Surface Water Studies
4.1 Calculating Flood Recurrence Intervals
Introduction
The Task
Data Source
Procedure For Part 1
Procedure For Part 2
Using Your Graph
Epilogue
Calculating Flood Recurrence Intervals Work Sheet
Worksheet
4.2 The Deposition of Sediments
Introduction
Materials Needed
Setup
Practice Run
The Experiment
Calculations
Graphing
Worksheet
The Deposition of Sediments Graph
4.3 River Study Lab 3: Determining Stream Discharge in the Field
Introduction
Materials Needed
Procedure
Additional Data Collection
Worksheet
Results

Chapter 5 Understanding Porosity & Permeability
Porosity and Permeability
Introduction
Part I: Determining Porosity
Procedure
Part II: Determining Permeability
Procedure
Data Tables for Porosity & Permeability Experiment
Calculations For Porosity & Permeability Lab
Part I: Calculating Porosity
Part II: Calculating Permeability
Part III: Calculating Retention Percentage
Summary and Application Questions
Sediment Size & Porosity
Sediment Size & Drainage Rate

Chapter 6 Topographic Maps
Introduction
Location
Understanding Latitude & Longitude
Orientation
Map Scale
A Few More Important Vocabulary Terms
Purpose
6.1 Exploring a Topographic Quadrangle Map
6.2 Constructing Topographic Maps
How to Contour
Golden Rules of Contouring
Contouring Tips
Constructing a Topographic Profile
Vertical Exaggeration of Topographic Profiles
Contouring Exercise #1
Topographic Profile #1
Contouring Exercise #2
Topographic Profile #2

Chapter 7 Exploring Earthquakes
7.1 A Seismic Wave Study
Introduction
Materials Needed
Procedure
7.2 Determining Earthquake Epicenter Location Through Triangulation
Introduction
Objective
Procedure
Appendices
Metric Conversion
Periodic Table of the Elements
Guidelines for a Formal Laboratory Write Up
Introduction
Procedure
Data
Calculations
Results
Conclusion
Discussion
Topographic Map Symbols


Geosciences and Environmental Change Science Center

GECSC staff are responsible for the development of data and tools that support global environmental research, landscape change investigations, geologic studies and emergency response activities.

Data release for Oxygen isotopes in terrestrial gastropod shells track Quaternary climate change in the American Southwest

Recent studies have shown the oxygen isotopic composition (delta18O) of modern terrestrial gastropod shells is determined largely by the delta18O of precipitation. This implies that fossil shells could be used to reconstruct the delta18O of paleo-precipitation as long as the hydrologic pathways of the local watershed and the shell isotope systematics are well understood.

Measured sections and paleocurrent data from fluvial deposits of the Upper Cretaceous-Paleogene Raton and Poison Canyon Formations, Raton Basin, Colorado-New Mexico, USA

This document provides two data sets that characterize outcrops of fluvial deposits of the Upper Cretaceous-Paleogene Raton and Poison Canyon Formations of the Raton Basin of Colorado-New Mexico, USA. First, the dataset includes stratigraphic sections measured through fluvial deposits of the Raton and Poison Canyon Formations (ten unique .tif files), currently exposed in roadside outcrops.

Supporting data for Physical and chemical evidence for an aeolian component of paleowetland deposits

The Las Vegas Formation (LVF) is a well-characterized sequence of groundwater discharge (GWD) deposits exposed in and around the Las Vegas Valley in southern Nevada. Nearly monolithologic bedrock surrounds the valley and provides an excellent opportunity to test the hypothesis that GWD deposits include an aeolian component.

Luminescence, weather, and grain-size data from eastern Chuckwalla Valley, Riverside County, California

This data release contains luminescence, weather, and sediment grain-size data from eastern Chuckwalla Valley, Riverside County, California. This study investigates sedimentary and geomorphic processes in eastern Chuckwalla Valley, Riverside County, California, a region of arid, basin-and-range terrain where extensive solar-energy development is planned. The objectives were to (1) measure.

Data release for Climatically driven displacement on the Eglington fault, Las Vegas, Nevada, USA

The Eglington fault is one of several intrabasinal faults in the Las Vegas Valley, Nevada, USA, and is the only one recognized as a source for significant earthquakes.

Petrology of the postcaldera intrusions associated with the Platoro caldera system, Southern Rocky Mountains Volcanic Field, Colorado

The dataset includes whole-rock geochemistry, phenocryst/mineral trace element compositions, zircon U–Pb geochronology, and zircon in situ Lu–Hf isotopes for intrusions associated with the Oligocene Platoro caldera complex of the San Juan volcanic locus in Colorado features numerous exposed plutons, both within the caldera and outside its margins, enabling investigation of the timing and.

Biomes simulated by BIOME4 using CESM2 lig127k, midHolocene, and piControl climate data on a global 0.5-degree grid

This data set consists of simulated biomes for the last interglacial (127 ka), middle Holocene (6 ka), and preindustrial (1850 CE) time periods displayed in Figure 14 of Otto-Bliesner et al. (2020). Biomes were simulated with BIOME4 (ver. 4.2, https://pmip2.lsce.ipsl.fr/synth/biome4.shtml Kaplan et al., 2003.

Landscape inputs and simulation output for the LANDIS-II model in the Greater Yellowstone Ecosystem

This data release provides inputs needed to run the LANDIS-II landscape change model, NECN and Base Fire extensions for the Greater Yellowstone Ecosystem (GYE), USA, and simulation results that underlie figures and analysis in the accompanying publication. We ran LANDIS-II simulations for 112 years, from 1988-2100, using interpolated weather station data for 1988-2015 and downscale

Data release for: Spatially explicit reconstruction of post-megafire forest recovery through landscape modeling

This data release provides inputs needed to run the LANDIS PRO forest landscape model and the LINKAGES 3.0 ecosystem process model for the area burned by the Black Dragon Fire in northeast China in 1987, and simulation results that underlie figures and analysis in the accompanying publication. The data release includes the fire perimeter of Great Dragon Fire input data for LINKAGES including.

Data release for Accounting for Land in the United States: Integrating Physical Land Cover, Land Use, and Monetary Valuation

Land plays a critical role in both economic and environmental accounting. As an asset, it occupies a unique position at the intersection of the System of National Accounts (SNA), the System of Environmental-Economic Accounting Central Framework (SEEA-CF), and (as a spatial unit) SEEA Experimental Ecosystem Accounting (SEEA-EEA), making land a natural starting point for dev

Data release for tracking rates of post-fire conifer regeneration distinct from deciduous vegetation recovery across the western U.S.

Post-fire shifts in vegetation composition will have broad ecological impacts. However, information characterizing post-fire recovery patterns and their drivers are lacking over large spatial extents. In this analysis we used Landsat imagery collected when snow cover (SCS) was present, in combination with growing season (GS) imagery, to distinguish evergreen vegetation from deciduou

Elevation of top of Precambrian rocks from previous USGS studies of the Colorado Plateau

For use as part of a regional petroleum assessment, the USGS in the early 1990’s developed a dataset reporting elevation on the surface of the Precambrian basement of the central and southern Colorado Plateau and vicinity (Butler, 1991). This dataset was released as paper report that included a table of basement elevations at more than 3,700 control points, including outcrop d


Luster Rocks Kit

Luster is the physical property of minerals which describes the appearance of reflected light from fresh mineral surfaces. Lusters fall into two basic categories: Metallic (opaque and metal-like) and Non-metallic (transparent in fine thin particles immersed in luquid.)

The surface appearance of non-metallic minerals is further described as being adamantine (brilliantly reflecting), vitreous (bright and shiny such as broken glass), earthy, waxy, resinous, pearly, silky, greasy and dull.

With this 15 minerals luster set you get to explore all categories or both metallic and non-metallic luster.

Included Minerals:

NON-METALLIC:

  • Milky Quartz (vitreous)
  • Sulfur (resinous to greasy)
  • Microcline Feldspar (vitreous to pearly)
  • Rose Quartz (vitreous)
  • Nepheline (greasy to pearly)
  • Talc (greasy to pearly)
  • Calcite (subvitreous to vitreous)
  • Muscovite (vitreous to pearly)
  • Chalcedony (waxy to dull)
  • Satin Spar gypsum (silky)
  • Alabaster gypsum (dull to earthy)
  • Quartz crystal (adamantine)

Each mineral specimen is approximately 1 inch in diameter and is numbered (reference card is included.)


7.8: Luster - Geosciences

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Feature Papers represent the most advanced research with significant potential for high impact in the field. Feature Papers are submitted upon individual invitation or recommendation by the scientific editors and undergo peer review prior to publication.

The Feature Paper can be either an original research article, a substantial novel research study that often involves several techniques or approaches, or a comprehensive review paper with concise and precise updates on the latest progress in the field that systematically reviews the most exciting advances in scientific literature. This type of paper provides an outlook on future directions of research or possible applications.

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to authors, or important in this field. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.


Physical Properties

Cleavage: <010>Distinct, <001>Distinct
Color: Iron black, Dark grayish black.
Density: 3.99 – 4.05, Average = 4.01
Diaphaneity: Opaque
Fracture:Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 5.5-6 – Knife Blade-Orthoclase
Luminescence: Non-fluorescent.
Luster: Sub Metallic
Streak: brownish black


Time Scavengers

Agathe here – The European Geoscience Union, EGU, a leading learned society in the fields of Earth, Planetary and space sciences, organize each year the largest European conference in geosciences. Due to COVID-19, this year’s conference was entirely virtual. Naturally, attending an online conference is very different from going to one in person: meeting people is less easy and you don’t feel the excitement of being surrounded by your colleagues and friends, not to mention that it is difficult when you are in front of your computer to put your work in progress aside and devote yourself to the conference. I attended the EGU meeting to present results of my PhD work in paleoclimatology, on the evolution of continental climate from the mid-Eocene to the early Oligocene. As it was my first big 100% virtual conference, I would like to give my impressions on the format, a little bit particular, but which will certainly become more and more common in the future.

EGU (virtual) General Assembly 2021, vEGU21

Part I – Joining a fully virtual conference, what does it look like?

The number of participants at EGU General Assemblies increases from year to year, and this conference format will not have limited participation with 18,155 scientists from 136 countries this year against 16,273 participants from 113 countries in the last edition, in 2019 [1] . In recent years, various movements have developed that promote a lowering of greenhouse gas emissions associated with research activities: first aware of climate change, researchers must adapt their practices to be consistent and follow an energy-saving approach [2] . One of the positive points of this year’s meeting is that without all the flights to Vienna, its carbon imprint was much lower . Last April, the EGU estimated that by organizing a fully virtual conference with 18,000 participants, greenhouse gas emissions of the assembly would be equivalent to less than 0.1% of the same conference in person (despite the video stream) [3] !

Virtual vEGU21 hall (credit: EGU blogs, https://blogs.egu.eu/divisions/g/)

Normally, the conference hosts a large number of presentations including posters, 10-minute talks, and “PICOs” (Presenting Interactive COntent®), a format for short digital presentations, specific to the EGU. To give an idea, in 2019, the assembly counted 5531 orals, 9432 posters and 1287 PICOs [1] . In order to give everyone the opportunity to present results to a broad audience , the majority of this year’s presentations were in the form of PICOs, i.e. small 2-min-talks with a single slide! This was the case for my presentation. Fortunately, the EGU website also allowed presenters to add more content, so I also made a 20-minute video to present my work to the most interested speakers. What an exercise! Let’s face it, even if we like challenges, summarizing several months of work in 120 seconds is still a bit frustrating. But with hindsight, I think it was very interesting, reminding me of the 3 minutes thesis competitions , 3MT (these are really nice to see, if you never tried check here [4] ).

First of all, presenting your work in 2 minutes requires a lot of work to be done beforehand. How can I share the problematic and the interest of my work with my audience without presenting the different notions in detail? What are my main results? What is the take-home message? I think being used to talking about your research with your non-academic friends and family may really help. The conference offered the possibility to make this presentation live or to pre-record it. I choose the second option to make mine more accessible, by adding subtitles and to be able to archive it online after the conference. As a non-native speaker, I know that it can sometimes be difficult to follow a whole session of presentations, especially if they are not totally in our research topic, and depending on speakers’ accent. So, it was also an opportunity to make sure that this 2-minute message would get through to as many people as possible who came to listen. Finally, this format was also very interesting for the diffusion of the work . I now have a fairly simple 2-minute video associated with my in-progress publication. It’s still additional work to do, but I think I’ll practice this exercise again next time before I start writing an article, and then why not for its dissemination afterward! In spite of this particular format, moments of exchange were allowed in each session, through dedicated video conference rooms for each presenter. I had the pleasure to meet new researchers, saw friends and colleagues. Like in big music festivals, many sessions are held in parallel at EGU General Assemblies. With shorter, though dense, sessions, I think I was able to see more and a greater diversity of studies.

Part II – Thinking more

In parallel to sessions on my research theme (paleoclimates), which always teach a lot, the EGU offers the possibility to attend special (and longer), oral presentation, the Medal lectures , which allowed me to attend presentations by the eminent (paleo)climatologists Valérie Masson-Delmotte and Kim Cobb, and small courses (useful to nice to refresh one’s geology basics for example). What I really like about the EGU is that the conference also has great sessions (presentations, lectures or debates) about research in general and how to do it, for example: about the role of geosciences in the evolution of the world / about education and communication of science / or about diversity, equity and inclusion in science. This year, I was particularly impressed by two of them:

First, “ A Climate and Ecological Emergency: Can a pandemic help save us…? ”, with the passionating and super-positive intervention of the climatologist Katharine Hayhoe (see her website which gives a lot of tools to understand and raise awareness about climate change [5,6] ), who compared the rapidity of action on a global scale in response to COVID to the persistent lack of action of governments in the face of the ongoing climate crisis, trying to understand the origin of this crisis (ex. The phenomena of psychological distancing: COVID showed us that we could react quickly and limit our emissions, how can we do the same in the face of climate change? I was also particularly interested in the session, “ Promoting diversity in geosciences “, which took stock of the lack of diversity and neo-colonial practices within geosciences, and exposed concrete means to set up an anti-racism laboratory [7,8] . Budiman Minasny’s presentation introduced me to the concept of parachute science (aka helicopter research ) which is “ when researchers from wealthier countries go to a developing country, collect information, travel back to their country, analyze the data and samples, and publish the results with no or little involvement of local researchers “ [9] . One can imagine that perhaps some unscrupulous researchers take advantage of local researchers to do unrecognized research assistance work in the field, somewhere far away… There are people with a poor morality in all fields. However, I had never realized (in fact I had never asked myself), that there was a whole grey area with indirect and less obvious ways of misconducting. A striking example was for instance that by working on research questions centered on other countries, without involving local universities, we may grab potential research to local research communities… In my future research, I would like to address questions of macro-evolution on a global scale, although brief, this presentation would clearly have helped me thinking about my future collaborations. As a non-minoritized (although) woman, I am not the best person to talk about this topic, and I certainly still have tons of things to learn to be up to speed, but it is thanks to conferences like these that one learns little by little how to conduct fair science at the scale of one’s lab and internationally, so these should be promoted.

Prof. Katharine Hayhoe presenting the different psychological mechanisms associated to climate change inaction.

Short conclusion –

As already explained on this blog [9] , attending conferences is very important, especially for young researchers. Thanks to this meeting, I was able to see many presentations, meet researchers in my field, but also question the way I present my work and create materials to share it with more people. The development of this digital format also makes it possible to hold more conferences, especially since some of the smaller ones can be free. Yet, like most researchers, I think, I am looking forward to the experience of real conferences. This experience calls for questioning our practices: since we can do 100% virtual and low carbon conference, how far do we find it acceptable to travel to a conference?


Peaks this program fulfills

Required Core Courses (9 credits)

Three required core courses give students a foundation in the principles of physical and human geography, and introduce students to spatial analysis technologies and tools of Geographic Information Systems.

Course ID Course Name Number of Credits
GEO-150Physical Geography3 credits
ENV-151Introduction to Human Geography3 credits
ENV-350Introduction to Geographic Information System (GIS)2 credits
ENV-350LIntroduction to Geographic InformationSystem Lab1 credits

Take ONE laboratory course (4 credits)

Course ID Course Name Number of Credits
ENV-161Environmental Systems Science
ENV-161LEnvironmental Systems Science Lab
GEO-101Physical Geology3 credits
GEO-101LPhysical Geology Lab1 credits
BIO-140Idaho Natural History3 credits
BIO-140LIdaho Natural History Lab1 credits

Take ONE additional upper division elective course (3 credits)

The following four upper division elective options provide depth in geographic topics.

Course ID Course Name Number of Credits
ENV-357Applied Cartography3 credits
GEO-310Earth's Dynamic Climate System3 credits
GEO-320Watershed Hydrology3 credits
ENV-330Working Landscapes and Global Climate3 credits

Natural Sciences & Mathematics

Professional Studies & Enhancements


AGI Webinar Archive - May 2020

We hosted a couple of webinars in Portuguese in the month of May. We understand that it can be hard to find the time to attend (or even register for) these webinars, so we wanted to host them here for all to enjoy. Want to take part in our next webinar? Sign up for webinar alerts from us so that you get an early invitation email the next time we host one for your country/time zone. Seats are often limited so signing up for alerts is the best way to experience our webinars live!


4. Coupled U-Pb Zircon-Rutile Dating Applied to Sediment Provenance in the Eastern Himalayan-Indo-Burman Region

4.1. The Tibet-Himalaya-Indo-Burman Region

4.2. Modern U-Pb Zircon-Rutile Chronology of Eastern Himalayan-Tibet Drainages

12 and 8 Ma) exhibit two strikingly similar patterns also in terms of the <50 Ma population, with 10–20 Ma rutiles possibly derived from Himalayan sources south of the suture or from Lhasa magmatism.

500 Ma zircon age population (Figure 6d–l) that characterizes Indian-derived sediments and corresponds to the intrusion of late “Pan-African” granites [132]. In these samples, the 50–70 Ma population that is distinctive of the Gangdese Batholith in the Asian plate is lacking and

15–30 Ma zircon rims (up to 30% of the sample) testify to Cenozoic Himalayan metamorphism affecting GH [84]. Rutile in the same samples is dominated by late Miocene ages (youngest grains:

9–13 Ma), with some older components as old as Paleozoic probably derived from Tethyan sedimentary sources. Such

9–15 Ma rutile age signature testifies to the exhumation of GH following Himalayan metamorphism and is minor in the Yarlung Tsangpo upstream of the syntaxis but prominent in the Siang and Brahmaputra at locations S and Z (Figure 6a,o,p) receiving the contribution of tributaries draining the southern slopes of the Himalayan orogen dominated by GH. As previously mentioned (Section 3.2), Warren et al. [112] suggested that 10–11 Ma rutiles from granulite and amphibolite facies GH rocks constrain the timing of rapid cooling from peak T conditions of

650 °C at 12 Ma in the granulites and amphibolites, respectively.

1.4 Ma bedrock rutile from the Namche Barwa massif at the core of the syntaxial antiform, Section 3.2 Figure 7). The 50–70 Ma Gangdese Batholith zircon source and the “Pan-African” (

500 Ma) Indian component are also recognized in the two Brahmaputra samples S and Z. The comparison of samples W, S and Z constrains the evolution of the downstream signature along the main trunk of the Yarlung Tsangpo-Brahmaputra, with enhancement of the GH signature in sample S and the appearance of a

30% syntaxial component (<3 Ma). The latter, although reduced to

10%, is still preserved in sample Z several 100s km downstream.

400 °C ([133] and references therein). The overall younger age signature of detrital white mica from the Brahmaputra drainage basin (Figure 7a) primarily reflects the different response to cooling of the Ar-Ar chronometer compared to rutile and highlights its complementarity in tracking the same (or distinct) tectono-thermal events in the bedrock sources. As mentioned in Section 3.2, one of the best examples of how various geo- and thermo-chronometers altogether sensitive to T in excess of 800 °C down to approximately <100 °C respond differently to the same thermal event(s) is provided by the rapidly exhuming core of the eastern Himalayan syntaxis (ES in Figure 7b see summary Figure 2 of [84], [107] and references therein). Strikingly, the unique isotopic signature of the ES source, comprising an area of only ca. 40 km by 40 km, i.e., <0.5% of the entire Brahmaputra drainage basin (

580,000 km 2 [130]) is preserved even in the composite samples of Figure 7.

1.4 Ma rutile from the Namche Barwa massif [84]. The Himalayan metamorphic peak is identified by

15–40 Ma zircons [138], typically occurring as overgrowths on older zircons [42]. Circa 9–15 Ma rutiles and white micas in the same age range (but also as young as 3–6 Ma) likely testify to cooling following exhumation of Greater Himalayan rocks (GH) [84,137]. White micas in the range 4–20 Ma can also be contributed from the Asian plate (Lhasa) or Burma/Indo-Burman sources, although the latter show a large majority of ages > 20 Ma ([137] and references therein). Both the Asian and Burma plates show evidence for igneous sources as young as 10–15 Ma [139,140,141,142,143,144,145] note the 50–70 Ma detrital zircon population of the Brahmaputra sourced by the Gangdese Batholith (GB) [42]. Prominent pre-Himalayan rutile sources to the Brahmaputra detritus (e.g. in the range 100–200 Ma) are yet to be identified due to the lack of U-Pb rutile bedrock data in this region. Interestingly, 400–600 Ma rutile occurs in modern detritus eroded from both Lhasa and Burma. Late Pan-African (PA,

500 Ma) and older detrital zircon populations can derive from Himalayan (i.e., Indian-derived sediments), Asian (Lhasa) or Burma bedrock sources. Erosion of Greater and Tethyan Himalayan (TH) units typically produces detrital zircon age distributions with main peaks at

0.5 and 0.8–1.2 Ga, while in Lesser Himalayan (LH) detritus the dominant U–Pb zircon age range is 1.7–2.0 Ga ([119,123] and references therein).

1.4 Ma rutile from the Namche Barwa massif [84]. The Himalayan metamorphic peak is identified by

15–40 Ma zircons [138], typically occurring as overgrowths on older zircons [42]. Circa 9–15 Ma rutiles and white micas in the same age range (but also as young as 3–6 Ma) likely testify to cooling following exhumation of Greater Himalayan rocks (GH) [84,137]. White micas in the range 4–20 Ma can also be contributed from the Asian plate (Lhasa) or Burma/Indo-Burman sources, although the latter show a large majority of ages > 20 Ma ([137] and references therein). Both the Asian and Burma plates show evidence for igneous sources as young as 10–15 Ma [139,140,141,142,143,144,145] note the 50–70 Ma detrital zircon population of the Brahmaputra sourced by the Gangdese Batholith (GB) [42]. Prominent pre-Himalayan rutile sources to the Brahmaputra detritus (e.g. in the range 100–200 Ma) are yet to be identified due to the lack of U-Pb rutile bedrock data in this region. Interestingly, 400–600 Ma rutile occurs in modern detritus eroded from both Lhasa and Burma. Late Pan-African (PA,

500 Ma) and older detrital zircon populations can derive from Himalayan (i.e., Indian-derived sediments), Asian (Lhasa) or Burma bedrock sources. Erosion of Greater and Tethyan Himalayan (TH) units typically produces detrital zircon age distributions with main peaks at

0.5 and 0.8–1.2 Ga, while in Lesser Himalayan (LH) detritus the dominant U–Pb zircon age range is 1.7–2.0 Ga ([119,123] and references therein).

4.3. Coupled U-Pb Zircon-Rutile Chronology Applied to Cenozoic Himalayan-Indo-Burman Sediment Repositories

25% of the grains <9 Ma interpreted as derived from the erosion of the eastern syntaxis, hence supporting the interpretation of the Brahmaputra flowing in the Himalayan foreland at Dungsam Chu by

5 Ma, the timing of the deposition of sample SJ8.

80–100 Ma population prominent in Paleocene−Eocene samples (e.g., samples Y3-81 and MY16-64A in Figure 10), less prominent in Oligocene samples and subordinate by Miocene times when a

50–75 Ma population becomes dominant (e.g., samples Y3-13 and MY16-56A in Figure 10).

400 and 600 Ma, presumably derived from the Burmese basement. A modest contribution of rutile grains between 40 and 80 Ma is recorded in the middle Oligocene surface outcrop samples, with a

40 Ma population dominating by the time of deposition of the subsurface upper Oligocene sample and in the rest of the overlying succession. These

40 Ma rutiles are interpreted as derived from the erosion of the exhumed Mogok Metamorphic Belt to the east of the Sagaing fault. A positive εHf signature determined for the Mesozoic–Cenozoic detrital zircons in the rocks of Eocene age and older is interpreted to be derived from a local igneous source, likely the Western Myanmar Arc. In contrast, Miocene samples include a substantial additional population of grains with negative εHf values, compatible with derivation from the Eastern Batholiths (typically εHf < 0) rather than from the Gangdese Batholith of the Transhimalaya (typically εHf > 0). Such a change in provenance between the Eocene and the Miocene was interpreted in terms of the MMB and Eastern Batholiths becoming a significant new source region providing detritus to the CMB through establishment of a paleo–Irrawaddy trunk river by middle Oligocene times, without requiring a paleo Yarlung Tsangpo-Irrawaddy connection (Figure 21 of Zhang et al. [110]).

500 Ma peak typical of GH and TH as well as older zircons (Figure 11 cf. the Brahmaputra signature in Figure 6 and Figure 7). Mesozoic and Cenozoic populations with broad peaks at ca. 50–60 and 110–130 Ma (consistent with derivation from the Transhimalaya of the Lhasa Terrane) increase up-section and include a minor population of

15–40 Ma zircon grains likely testifying to the Himalayan high grade metamorphism and leucogranites or Lhasa magmatism ([108] cf. Figure 7b). Importantly, in the Bengal Fan, Transhimalayan zircons have been found from the base of the fan, dated at 18 Ma at that location [108], consistent with an established Yarlung Tsangpo–Brahmaputra connection by that time [42].

500–600 Ma source (identified in modern detritus eroded from the Lhasa terrane, Figure 6b, but also present in the modern Dhansiri River draining the IBR, Figure 6m) or the 10–15 Ma GH source (Figure 6d–l and Figure 7).


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