Diamonds are often seen as symbols of luxury and beauty, but beneath their dazzling exterior lies a treasure trove of geological secrets. These precious stones are much more than just a product of deep Earth conditions—they serve as remarkable time capsules, preserving information about the Earth’s mantle dynamics. The mantle, which makes up the majority of Earth’s interior, is a layer rich in both mystery and activity. By studying diamonds, scientists have been able to unlock some of the most profound insights about the processes that occur deep within our planet.

In this blog, we’ll explore how diamonds reveal secrets about Earth’s mantle dynamics and why they are crucial to understanding the complex behavior of our planet’s interior.

1. Diamonds: A Glimpse into the Deep Earth

Diamonds form under extreme conditions, typically at depths of 140 to 190 kilometers (87 to 118 miles) below the Earth’s surface in the mantle. This depth places them far beyond the reach of typical geological observations, so diamonds become one of the few natural objects that can provide direct insight into the conditions and processes occurring in the Earth’s deep interior.

As these diamonds crystallize in the mantle, they capture and trap tiny inclusions—microscopic traces of the surrounding mantle environment. These inclusions are often composed of minerals and gases that have been subjected to immense pressure and temperature, making them invaluable for studying the composition and behavior of the mantle.

2. Diamonds as Time Capsules of Carbon

The formation of diamonds is closely tied to the carbon cycle deep within the Earth. Carbon, an essential building block of life, behaves differently at extreme depths. Diamonds crystallize when carbon atoms bond under high-pressure conditions, forming a crystalline lattice structure. This process can take millions to billions of years, and each diamond’s unique formation history offers a snapshot of carbon’s behavior in Earth’s mantle over geological time.

By examining the carbon isotopes trapped inside diamonds, scientists can better understand the movement of carbon through the Earth’s mantle. This carbon cycling is crucial for understanding global climate patterns, as the mantle acts as both a source and sink for carbon, influencing long-term climate stability. Diamonds provide a record of this deep carbon cycle, helping scientists reconstruct past climate conditions and predict future climate changes.

3. Mantle Convection and Diamond Formation

The movement of Earth’s mantle is driven by mantle convection—large-scale flows of material caused by heat from the Earth’s core. These convective currents play a significant role in shaping the geological processes that occur in the mantle, including the formation of diamonds.

Diamonds form in regions of the mantle where pressure and temperature are just right, typically at the boundaries of mantle convection cells. These cells are constantly moving, and as they carry material from the lower mantle toward the surface, they can trigger the formation of diamonds under certain conditions. Studying the diamonds’ inclusions can reveal where and how mantle convection occurs, helping geologists understand the flow of heat and material within the Earth.

In particular, diamonds with inclusions of certain minerals, such as peridotite or eclogite, can indicate the nature of mantle convection cells and the geological processes that occur at these depths. By analyzing these inclusions, scientists can identify whether the mantle is in a state of upwelling or downwelling, providing critical insights into how mantle dynamics shape the Earth’s surface.

4. Diamonds and the Composition of the Mantle

The composition of the Earth’s mantle has been a subject of much scientific inquiry, as it influences everything from volcanic activity to plate tectonics. Diamonds serve as natural probes into the mantle’s chemical composition, as their inclusions can contain tiny fragments of minerals and gases that were trapped as they formed.

For example, some diamonds contain inclusions of olivine, a mineral that is abundant in the upper mantle. Other diamonds may contain minerals like garnet or pyroxene, which offer clues about the mineral makeup of deeper mantle layers. By analyzing these inclusions, scientists can better understand the types of minerals present in the mantle and how these minerals interact during mantle convection.

Diamonds also offer clues about the presence of volatile elements, such as nitrogen and hydrogen, which are integral to understanding the behavior of the mantle and its interactions with the Earth’s surface. These elements can influence the physical properties of the mantle, such as its viscosity and the way it responds to pressure changes.

5. Diamonds as Markers of Subduction Zones

One of the most fascinating revelations that diamonds offer comes from their relationship with subduction zones. Subduction occurs when one tectonic plate is forced beneath another, sending material deep into the mantle. Diamonds that form in these environments are particularly valuable because they provide insights into how material is recycled in the Earth’s interior.

Inclusions found in diamonds that form in subduction zones can contain minerals and gases from the oceanic crust, offering clues about how Earth’s surface and mantle are interconnected. These diamonds can reveal how subducted material undergoes metamorphic changes under high pressure and temperature, contributing to the recycling of Earth’s material over geological timescales.

6. Unlocking Earth’s Ancient Past

Some diamonds, known as “super-deep” diamonds, are believed to have formed at depths of over 700 kilometers (435 miles) beneath the Earth’s surface. These rare diamonds offer an unparalleled opportunity to study the conditions of the Earth’s lower mantle, a region that is otherwise inaccessible to scientific investigation.

Super-deep diamonds often contain inclusions of minerals that have been subjected to extreme pressures and temperatures, offering clues about the ancient, primordial Earth. These diamonds provide insight into the early stages of the Earth’s formation and the behavior of material deep in the planet’s interior. They also offer a window into the processes that shaped the formation of the Earth’s continents and ocean basins.

Conclusion

Diamonds are far more than just beautiful gemstones. They are invaluable windows into the hidden world of Earth’s mantle, offering scientists a direct glimpse into the processes and materials that make up our planet’s interior. From carbon cycling and mantle convection to the recycling of material in subduction zones, diamonds help us unlock the mysteries of the Earth’s dynamic processes.

By studying these remarkable time capsules, we gain a deeper understanding of how our planet has evolved and continues to change. As technology advances and our ability to analyze diamond inclusions improves, we can expect even more groundbreaking discoveries about the Earth’s mantle dynamics, all thanks to these ancient treasures formed deep within our planet.

Diamonds have long been cherished for their brilliance and rarity, but they are much more than just precious gemstones. These remarkable minerals offer scientists valuable insights into the deep processes of Earth’s mantle. Formed under extreme pressure and temperature conditions, diamonds are essentially time capsules, preserving a record of the Earth’s inner workings. In this blog post, we will explore the role of diamonds in mantle geodynamics, highlighting how these natural wonders are helping researchers understand Earth’s complex carbon cycle and mantle dynamics.

1. What is Mantle Geodynamics?

Before we dive into the relationship between diamonds and mantle geodynamics, it’s important to understand what mantle geodynamics refers to. The Earth’s mantle, located beneath the crust and above the core, is a dynamic region that plays a key role in the planet’s geological processes. Mantle geodynamics is the study of the physical movements and interactions that occur within this vast and mostly inaccessible part of the Earth.

These processes are responsible for phenomena such as plate tectonics, volcanic activity, and the long-term evolution of Earth’s interior. Understanding the behavior of the mantle is crucial to understanding not only the structure of the Earth but also the cycling of elements like carbon, which is fundamental to life on Earth.

2. Diamonds as Earth’s Deep Messengers

Diamonds form under the intense pressure and high temperatures found deep within the Earth’s mantle, typically at depths of 140 to 190 kilometers (87 to 118 miles). This means that diamonds can act as direct messengers from the Earth’s interior, carrying with them information about conditions at these extreme depths. While most diamonds are formed in the mantle, only a tiny fraction of them make their way to the Earth’s surface through volcanic eruptions, where they are then mined and studied.

The unique structure of diamonds allows them to trap tiny inclusions of material from their surrounding environment, making them ideal for geoscientists who are trying to understand the conditions of the mantle during their formation. These inclusions can contain minerals, gases, and even small pockets of carbon that provide a snapshot of the Earth’s deep carbon cycle and mantle dynamics.

3. Diamonds and the Deep Carbon Cycle

Carbon is one of the most abundant elements in Earth’s interior, and it plays a central role in the Earth’s geodynamics. The deep carbon cycle refers to the movement of carbon between the Earth’s surface, mantle, and core over geological timescales. Carbon enters the mantle primarily through subduction, where oceanic plates carrying carbon-rich materials like sediment are forced down into the mantle. Some of this carbon is released back to the surface through volcanic eruptions, while the rest remains trapped in the mantle, often in the form of diamonds.

Diamonds are thought to contain traces of carbon from the mantle’s early history, offering crucial insights into how carbon has been stored and cycled over millions and billions of years. By studying diamonds, scientists can better understand the processes that govern the storage, transformation, and release of carbon deep within the Earth, including how it influences mantle convection, plate tectonics, and volcanic activity.

4. How Diamonds Reveal Mantle Composition and Processes

Diamonds are not just carbon crystals; they are also filled with tiny inclusions of minerals that provide clues about the composition of the mantle at various depths. These inclusions, also known as “mineral inclusions” or “inclusions,” offer a rare and direct window into the mantle’s mineralogy and temperature conditions.

By analyzing these inclusions, scientists can infer the types of rocks and minerals present in the mantle and determine the temperature and pressure conditions at the time of diamond formation. For example, inclusions of minerals such as pyroxene, garnet, or olivine can tell geoscientists about the specific depth and environment in which the diamond formed. In addition, diamonds formed in different parts of the mantle, such as the upper mantle or the lower mantle, may carry different inclusions that reflect the varying conditions at those depths.

These inclusions are key to understanding mantle convection, the process by which heat and material circulate within the mantle. Mantle convection drives plate tectonics and contributes to the recycling of Earth’s materials. By studying the mineral inclusions in diamonds, scientists can gain insight into how the mantle flows and how carbon moves throughout the deep Earth.

5. The Role of Diamonds in Understanding Earth’s Evolution

Diamonds formed in the Earth’s mantle provide clues not only about the present-day processes in the mantle but also about the planet’s geological history. Because diamonds are incredibly stable, they can survive the long journey from the depths of the mantle to the Earth’s surface without losing their original characteristics. This allows them to preserve information about the mantle’s conditions when they first formed.

By studying diamonds from different geological periods, scientists can track how the Earth’s mantle has evolved over time. This includes changes in the carbon cycle, mantle composition, temperature, and pressure. For example, some diamonds have been found to contain inclusions of carbon that suggest the presence of deep carbon reservoirs, which could help explain the Earth’s long-term climate regulation.

6. Diamonds and the Possibility of New Discoveries

As research into diamonds and mantle geodynamics continues to evolve, new discoveries are being made that deepen our understanding of Earth’s interior. Advances in technology, such as more sophisticated diamond analysis techniques, have allowed scientists to probe these tiny inclusions with greater precision. As we learn more about the formation and composition of diamonds, we also uncover new details about the complex geodynamics of the mantle and the deep carbon cycle.

The study of diamonds may also provide insights into broader planetary processes, such as the formation of other rocky planets and the behavior of carbon on planets beyond our own. As we explore more about the deep Earth, diamonds will continue to be valuable tools for understanding our planet’s past, present, and future.

Conclusion: Diamonds as a Key to Unlocking Earth’s Deep Secrets

Diamonds are not just precious gems; they are valuable scientific tools that offer a rare glimpse into the deep Earth’s mantle geodynamics. Through their unique structure and the mineral inclusions they contain, diamonds help scientists explore the complex processes of mantle convection, carbon cycling, and Earth’s geological evolution. By studying these natural wonders, we are able to uncover the mysteries of our planet’s interior and gain a deeper understanding of the forces that shape Earth’s history and future.

The Earth’s mantle, a vast and mysterious region beneath the crust, plays a crucial role in shaping the planet’s geology and sustaining life. But how do we unlock the secrets of this deep, inaccessible part of our planet? The answer lies, in part, within one of the most coveted substances on Earth: diamonds.

While diamonds are renowned for their beauty, they also provide critical insights into the deep processes occurring in the Earth’s interior, particularly regarding the carbon cycle in the mantle. Let’s explore how diamonds help us understand the movement of carbon deep within the Earth and why this is important for both geologists and environmental scientists alike.

Diamonds: Nature’s Window to the Deep Earth

Diamonds form under extreme conditions of pressure and temperature, deep within the Earth’s mantle, typically at depths between 140 to 190 kilometers (87 to 118 miles). These conditions are far beyond the reach of direct human exploration, so understanding the mantle has traditionally been a challenge. However, diamonds that form under these high-pressure conditions often contain trace elements and inclusions, including carbon, that provide valuable clues about the environment in which they formed.

Diamonds, therefore, act as natural time capsules. When they are brought to the Earth’s surface via volcanic eruptions, they carry with them information about the conditions in the mantle at the time of their formation. This allows scientists to study the processes taking place deep below the Earth’s surface without having to directly access it.

The Role of Carbon in the Mantle

Carbon is an essential element in Earth’s composition, and it plays a critical role in the mantle’s geodynamics. The mantle contains a significant amount of carbon, stored in a variety of forms, including carbonates and organic molecules. But how does carbon move through the mantle? And how does it impact geological processes?

The mantle’s carbon cycle is largely driven by tectonic activity. As tectonic plates shift and interact, carbon stored in the Earth’s crust is transported into the mantle, where it can undergo transformations. In some cases, carbon is released back to the surface during volcanic eruptions. In others, carbon can be sequestered in the mantle, where it may remain for millions of years.

Diamonds provide key evidence of the processes that govern carbon in the mantle. Researchers have discovered that diamonds often contain inclusions of carbon-bearing minerals, such as graphite, which help to reveal how carbon is stored, transported, and even transformed in the mantle. By studying these inclusions, scientists can gain a better understanding of the pathways that carbon follows deep within the Earth.

How Diamonds Help Reveal the Carbon Cycle

While diamonds are predominantly composed of pure carbon, the study of their inclusions reveals much more about the Earth’s carbon cycle. These inclusions often contain tiny minerals, such as silicates or carbonates, that were trapped in the diamond as it formed. These trapped minerals serve as a snapshot of the conditions in the mantle at the time of the diamond’s creation.

For instance, scientists have found that certain diamonds contain inclusions of carbonate minerals, which suggests that the mantle holds carbon in a stable form for long periods of time. This is crucial for understanding the long-term carbon cycle of the Earth, which plays a significant role in regulating the planet’s climate.

Additionally, the study of diamond formation processes helps scientists understand the temperature and pressure conditions under which carbon behaves in different ways. Some diamonds form under conditions of relatively low pressure, while others form under extreme conditions deep within the mantle. These variations provide insights into how the mantle’s carbon cycle changes at different depths.

The Significance of Diamonds in Understanding Earth’s Climate

The carbon stored in the mantle is an integral part of the Earth’s overall carbon cycle, which is closely linked to the planet’s climate system. Carbon dioxide (CO2) from the mantle can be released into the atmosphere during volcanic eruptions, where it can contribute to the greenhouse effect and influence global temperatures. Conversely, carbon can also be sequestered in the mantle over geological time scales, helping to regulate atmospheric CO2 levels.

Understanding how carbon moves through the mantle is crucial for scientists who are studying climate change. By examining diamonds, researchers can gain valuable insights into the long-term processes that regulate carbon storage and release in the Earth’s interior, which ultimately affects the atmosphere and climate.

The Future of Diamond and Mantle Research

As technology advances, scientists are developing increasingly sophisticated methods for studying diamonds and their inclusions. Techniques such as high-resolution imaging, laser spectroscopy, and chemical analysis are allowing researchers to delve even deeper into the properties of diamonds and their role in the Earth’s carbon cycle.

Future research will continue to explore how diamonds can provide a more detailed picture of the mantle’s carbon dynamics, as well as the broader geodynamic processes that shape our planet. By further understanding the movement of carbon in the Earth’s mantle, scientists will be better equipped to predict climate changes and mitigate their impacts on the planet.

Conclusion

Diamonds are more than just beautiful gemstones; they are valuable scientific tools that offer unique insights into the deep Earth, particularly the complex carbon cycle that drives mantle geodynamics. By studying the carbon inclusions in diamonds, scientists are unlocking the mysteries of the Earth’s interior and gaining a better understanding of the processes that shape our planet’s climate and geology.

As research on diamonds and the mantle progresses, we continue to learn more about the Earth’s deep carbon cycle, providing crucial information for everything from climate science to geodynamics. So, next time you admire the sparkle of a diamond, remember that it may just be a glimpse into the deep, carbon-driven forces shaping our world.

Diamonds are often seen as the epitome of luxury and beauty, but these precious gems hold much more than just aesthetic value. They offer a unique insight into the processes happening deep within the Earth’s mantle, providing scientists with critical information about the behavior of carbon in the Earth’s interior. By studying diamonds, geologists are unlocking the secrets of carbon’s journey through the planet’s inner layers, helping us better understand everything from the carbon cycle to the Earth’s geological history.

What Are Diamonds and How Do They Form?

Diamonds are formed under extreme pressure and temperature conditions that exist deep within the Earth’s mantle. The Earth’s mantle is a layer of hot, dense rock that lies beneath the crust and extends down to about 2,900 kilometers (1,800 miles). In these harsh conditions, carbon atoms are forced into a crystalline structure, forming the iconic diamond we see at the surface.

While diamonds can form in several geological settings, the most famous diamonds are formed in “diamond stability zones,” where the pressure and temperature conditions are just right. These diamonds are often carried to the Earth’s surface through volcanic eruptions, where they are eventually mined. What’s remarkable about diamonds is that they can encapsulate information about the mantle conditions at the time of their formation, including the type of carbon they contain.

Diamonds as Carbon Time Capsules

Diamonds serve as “time capsules” of the Earth’s deep history. Within their crystal lattice structure, diamonds can trap and preserve ancient fluids and gases, including carbon, that existed when the diamond was formed. By studying these inclusions, scientists can learn about the composition of the mantle during different geological periods.

The carbon found in diamonds is typically derived from the Earth’s mantle, but it can have different isotopic signatures depending on the conditions at the time of formation. Isotopes are variants of elements with different numbers of neutrons. For example, the ratio of carbon-12 to carbon-13 isotopes in a diamond can reveal important details about the source of the carbon, whether it came from deeper layers of the mantle or from surface materials that were subducted deep into the Earth. This allows scientists to track the movement of carbon through the mantle over time.

The Geodynamics of Carbon in the Mantle

Understanding how carbon behaves in the mantle is crucial for several reasons, particularly in the context of the global carbon cycle. Carbon plays a central role in the Earth’s geology, atmosphere, and climate system. It is one of the most important greenhouse gases, influencing the planet’s climate, and it is a key element in the formation of life.

Diamonds help geologists understand the pathways carbon takes within the mantle. The Earth’s mantle acts as a vast storage area for carbon, which can be released back into the atmosphere through volcanic eruptions. By studying diamonds, scientists can uncover the processes that control the movement of carbon from the mantle to the surface, and how it cycles through the Earth’s interior. This research is vital for understanding the Earth’s carbon storage and release mechanisms, which have long-term implications for global climate patterns.

Diamonds and the Carbon Cycle

The carbon cycle refers to the continuous movement of carbon through the atmosphere, oceans, soil, and rocks. Carbon is stored in various forms throughout the Earth, including in fossil fuels, carbonate minerals, and, notably, in diamonds deep within the mantle. Understanding how carbon is stored and transported within the mantle can help scientists predict how carbon behaves over geological timescales.

Recent studies of diamond inclusions have shown that carbon can be sequestered in the mantle for millions to billions of years, trapped in deep reservoirs that are not easily accessible. However, carbon is not permanently locked away. It can be released into the atmosphere through volcanic activity, where it can contribute to the greenhouse effect. The study of diamond geodynamics helps researchers better understand these processes, and the timescales involved in carbon sequestration and release.

Carbon and Mantle Dynamics: A Glimpse into Earth’s Past

Diamonds are more than just geological curiosities; they provide a snapshot of the Earth’s ancient history. Carbon isotopes trapped in diamonds can reveal information about the Earth’s geological processes, including mantle convection, plate tectonics, and volcanic activity. By analyzing diamond inclusions, scientists can trace the evolution of the mantle, the movement of tectonic plates, and how these processes have shaped the Earth’s carbon cycle over time.

This information is crucial for understanding not only Earth’s past but also its future. The study of diamonds allows scientists to refine models of how carbon behaves within the Earth, helping to predict the long-term effects of carbon release and storage on the climate. As scientists continue to study diamonds and their unique carbon signatures, they are unlocking a treasure trove of information about the Earth’s deep, hidden systems.

Conclusion

Diamonds, while primarily known for their beauty and rarity, are much more than mere gemstones. They are natural records of the Earth’s deep geological history, holding within them secrets of carbon’s journey through the planet’s mantle. By studying diamonds, scientists are uncovering the intricate dynamics of how carbon moves through the Earth, contributing to a deeper understanding of the planet’s carbon cycle, its climate history, and the forces that drive geological processes.

As research in diamond geodynamics continues to evolve, these precious gems will undoubtedly continue to shed light on the mysteries of the Earth’s inner workings and the role of carbon in shaping our planet’s past, present, and future.

Diamonds have fascinated humans for centuries, celebrated for their beauty and rarity. Yet, beyond their allure as precious gemstones, diamonds hold the key to understanding some of Earth’s most profound geological processes. These sparkling gems are formed deep within the Earth’s mantle, where extreme temperatures and pressures transform carbon into one of the most durable materials on Earth. But what role does carbon play in this process, and how does it shape our understanding of Earth’s internal dynamics?

In this blog, we will delve into the important role carbon plays in the mantle, and how it contributes to the formation of diamonds. By studying diamonds, scientists can gain invaluable insights into the behavior of carbon deep beneath the Earth’s surface and better understand mantle dynamics and the broader geodynamic processes that influence the Earth’s geology.

The Role of Carbon in Earth’s Mantle

The Earth’s mantle, located just beneath the Earth’s crust, stretches over 2,900 kilometers deep. Despite being far from the surface, the mantle is crucial for understanding the behavior of many elements, including carbon. Carbon plays a central role in the mantle’s processes, influencing the Earth’s long-term climate, tectonic activity, and even the formation of precious gems like diamonds.

In the mantle, carbon primarily exists in three forms:

1. Carbonates: Found in minerals like calcite and dolomite, carbonates form when carbon dioxide reacts with silicate minerals. These minerals are common in subduction zones, where oceanic plates are forced down into the mantle.

2. Graphite: At deeper levels of the mantle, carbon exists as graphite, which is stable under high-pressure and temperature conditions. Graphite is commonly found in the upper mantle and is considered a precursor to diamond formation at even greater depths.

3. Diamonds: Diamonds are the most well-known form of carbon in the mantle. They form under extreme conditions of pressure and temperature, at depths of about 140 to 190 kilometers beneath the Earth’s surface.

Each form of carbon plays a role in the geodynamics of the mantle, contributing to the cycling of carbon between the Earth’s surface and its deep interior.

From Carbon to Diamond: The Formation Process

Diamonds form when carbon atoms are subjected to extreme pressure and temperature conditions in the mantle. The carbon atoms bond in a specific arrangement to form a crystal structure known as the “diamond lattice.” This structure makes diamonds incredibly stable, dense, and the hardest known material on Earth.

Key Steps in Diamond Formation:

• High Pressure and Temperature: Diamonds are formed under extreme conditions, where temperatures range from 1,000 to 1,300 degrees Celsius, and pressures reach 45 to 60 kilobars—nearly 60,000 times the pressure we experience at sea level. These conditions cause carbon atoms to bond in a crystal structure that forms diamonds.

• Crystallization of Carbon: At these great depths, carbon is forced into a tightly packed arrangement, creating the crystalline structure that makes diamonds so durable. Over millions of years, carbon accumulates and crystallizes into diamonds, which are later transported to the Earth’s surface by volcanic eruptions.

• Inclusions and Trapping of Mantle Materials: Diamonds can also trap small fragments of surrounding mantle material, including gases, minerals, and even other carbon-based compounds. These inclusions provide clues about the environment in which the diamond formed, helping scientists learn more about the conditions within the mantle.

Diamonds often reach the Earth’s surface through volcanic eruptions, particularly from kimberlite pipes—deep, narrow tubes that connect the mantle to the surface. As these volcanic eruptions occur, diamonds are carried up, where they are eventually found in deposits, providing valuable information for researchers studying mantle processes.

The Importance of Carbon in Earth’s Carbon Cycle

The mantle plays a crucial role in the Earth’s carbon cycle, which governs the movement of carbon between the Earth’s surface and its deep interior. Carbon moves between the mantle and the atmosphere through processes like volcanic eruptions, subduction, and tectonic activity, which ultimately influence Earth’s climate and geology.

Carbon’s Role in Mantle Dynamics:

• Subduction and Recycling of Carbon: As tectonic plates move, carbon-containing materials, such as oceanic crust rich in carbonates, are pushed deep into the mantle in subduction zones. This process contributes to the recycling of carbon from the surface to the mantle.

• Volcanic Outgassing: When volcanoes erupt, they release carbon dioxide (CO₂) into the atmosphere. This outgassing is a crucial part of the carbon cycle, as it helps to balance the carbon that is subducted into the mantle. Over time, the Earth’s atmosphere and surface environment are influenced by the amount of carbon released by volcanic activity.

• Mantle Convection and Carbon Transport: Mantle convection refers to the movement of material within the mantle driven by heat from the Earth’s core. This process transports carbon and other volatile compounds, influencing both the formation of diamonds and the broader carbon cycle. The movement of carbon between the mantle and the surface helps regulate Earth’s climate over geological time scales.

Diamonds as Key to Understanding Carbon’s Behavior

Diamonds not only provide insights into carbon’s role in the mantle, but they also help scientists study other deep Earth processes. Diamonds are often found with inclusions—tiny fragments of mantle materials—trapped inside them as they form. By analyzing these inclusions, researchers can gain valuable insights into the composition and behavior of carbon at great depths.

Key Insights Gained from Diamond Inclusions:

• Mantle Composition: Inclusions in diamonds often contain rare minerals, gases, and isotopic signatures, allowing scientists to study the chemical composition of the mantle at depths that are otherwise inaccessible. This helps to improve our understanding of the materials present in the deep Earth.

• Carbon Isotope Analysis: Diamonds can also be used to analyze the isotopic composition of carbon. By studying the isotopes of carbon trapped in diamonds, researchers can gain insights into the history of carbon cycling in the mantle, and how it affects Earth’s climate over millions of years.

• Geodynamic Processes: The study of diamonds also helps to unravel the processes involved in mantle convection, plate tectonics, and subduction. As diamonds form, they record signals of deep mantle flow and material interactions, providing clues about the Earth’s geodynamic behavior.

Conclusion: Diamonds and Carbon

Diamonds are far more than just beautiful gemstones—they are natural time capsules that provide invaluable insights into the Earth’s deep interior. By studying diamonds and the role carbon plays in their formation, scientists are able to unlock mysteries about the Earth’s mantle, carbon cycling, and geodynamic processes. As we continue to explore the relationship between carbon and diamond formation, we deepen our understanding of the Earth’s geological processes and its long-term climate history.

Carbon’s journey from the surface to the mantle, and ultimately into diamonds, helps to shape our understanding of Earth’s evolution, from its early formation to the dynamic processes that continue to shape the planet today. The study of diamonds and carbon in the mantle is a crucial step in unraveling the complex geology of our planet.

Diamonds are one of the most coveted and enigmatic substances on Earth. They’re known for their exceptional beauty and rarity, but they also hold invaluable secrets about our planet’s inner workings. Formed under extreme pressure and temperature conditions, diamonds are more than just a symbol of luxury—they are nature’s time capsules, offering clues to the deep processes occurring in the Earth’s mantle.

In this blog, we explore how diamonds shape our understanding of mantle geodynamics, shedding light on the role of carbon in the Earth’s interior and the broader processes that govern our planet’s geological activities.

The Formation of Diamonds: A Glimpse into the Deep Earth

Diamonds are formed at depths of approximately 140 to 190 kilometers beneath the Earth’s surface, within the mantle. This region is far beyond the reach of conventional drilling, making diamonds one of the few natural samples of the deep Earth’s composition. They are created under extreme conditions: temperatures of about 1,000 to 1,300 degrees Celsius and pressures around 45 to 60 kilobars. These conditions allow carbon atoms to bond in a crystalline structure that is incredibly stable, leading to the creation of the world’s hardest known material.

The fact that diamonds form in such extreme conditions means they can serve as a window into the processes occurring deep in the mantle, especially the behavior of carbon, a fundamental element that plays a crucial role in the Earth’s geodynamics.

The Role of Carbon in Mantle Geodynamics

Carbon is a key element in the Earth’s mantle and is responsible for the formation of diamonds. But carbon doesn’t only form diamonds. It is a versatile element that can exist in various forms within the mantle, including as carbonates, graphite, and in volatile compounds like methane. By studying diamonds, scientists can learn about the behavior of carbon at great depths, which is crucial to understanding how it influences mantle dynamics.

The Earth’s mantle is largely composed of silicate minerals, but carbon is an important trace element. The behavior of carbon at depth is particularly significant for understanding key processes such as:

• Carbon Cycling: Carbon is involved in long-term processes that cycle between the Earth’s surface and its deep interior, including volcanic eruptions, tectonic plate movements, and the subduction of carbon-rich oceanic crust.
• Mantle Convection: The movement of materials within the mantle, driven by heat, is central to plate tectonics and volcanic activity. The presence of carbon can influence the physical properties of the mantle, affecting its convection patterns.
• Sequestration of Carbon: The process of carbon being trapped deep in the Earth (a process known as carbon sequestration) plays a role in regulating the planet’s climate over geological time scales. Understanding how carbon behaves deep in the Earth provides insight into the Earth’s long-term climate history.

Diamonds as Windows into Deep Mantle Processes

Diamonds not only provide a glimpse into the conditions at the moment of their formation, but they also offer unique insights into the processes that govern mantle geodynamics. This is because diamonds can encapsulate tiny inclusions—microscopic fragments of surrounding mantle material—trapping these samples deep within their structure. These inclusions can contain gases, minerals, and even other elements that were present in the mantle at the time the diamond formed.

By studying these inclusions, scientists can gain insights into the following:

• Mantle Composition: Inclusions in diamonds often contain rare minerals or gases, such as nitrogen or noble gases, which provide information about the composition of the deep mantle. This helps to build a more accurate model of how the mantle is structured and how it behaves under extreme pressure.
• Heat Flow: The study of diamonds can also help scientists understand the heat flow within the Earth’s mantle. Because diamonds are stable only under high-pressure, high-temperature conditions, they can act as markers for understanding temperature variations within the mantle.
• Mantle Processes: Diamonds can record the history of mantle processes, including mantle convection and the movement of tectonic plates. As diamonds form, they may record signals of deep mantle flow or material interactions, helping to reveal the ongoing geodynamic processes beneath the Earth’s surface.

Diamonds and the Deep Earth: Unraveling Mysteries of Earth’s Evolution

The study of diamonds has profound implications for understanding the Earth’s geological history and evolution. By investigating the diamonds’ age, formation conditions, and included materials, scientists can better understand how the mantle has evolved over millions of years. This, in turn, helps us piece together the history of Earth’s formation, tectonic activity, and climate changes.

For example, some of the oldest diamonds—forming around 3 billion years ago—may offer clues about the early Earth’s conditions and how it cooled over time. Additionally, diamonds from different geological environments may provide insights into regional differences in mantle composition and behavior.

Conclusion: The Crucial Link Between Diamonds and Mantle Geodynamics

Diamonds are far more than just precious stones—they are powerful tools that allow us to peer into the heart of the Earth’s mantle. Through their unique structure and the inclusions they contain, diamonds offer an unparalleled look at the behavior of carbon and other elements deep within the Earth. Their study enriches our understanding of mantle geodynamics, shedding light on the complex processes that shape our planet.

By continuing to study these natural wonders, we not only learn about carbon’s role in the Earth’s geological processes but also gain valuable insights into the Earth’s long-term evolution, climate history, and geodynamic activity. So, the next time you admire a diamond, remember—it’s not just a symbol of beauty, but also a key to unlocking the mysteries beneath our feet.

Super-deep diamonds, which form more than 380 km deep in Earth’s mantle, were invaluable tools for deep carbon scientists.

Super-deep diamonds, which form more than 380 km deep in Earth’s mantle, were invaluable tools for deep carbon scientists. Not only do they harbor clues about how they formed and therefore the reactions taking place inside Earth, they also trap small samples of mantle minerals, so-called inclusions, within their carbon crystal structure as they grow. These tiny samples of Earth’s deep interior from the region where the diamond forms were preserved under high pressure within a super-strong, unreactive diamond shell.

Many super-deep diamonds were small, have poor clarity, and were not generally used as gemstones. However, in a paper published in the journal Science, a team of researchers led by Evan Smith of the Gemological Institute of America (GIA) and including Deep Carbon Observatory DMGC (Diamonds and Mantle Geodynamics of Carbon) collaborators Steven Shirey (Carnegie Institution for Science, USA) and Fabrizio Nestola (Università degli Studi di Padova, Italy), suggests giant gemstone diamonds, like the 3106 carat Cullinan, were super-deep diamonds formed under special mantle conditions [1].

Co-author Professor Fabrizio Nestola explains the method of X-ray diffraction at the University of Padova, Italy. This method was used to first identify the presence of cohenite (an iron-nickel carbide) within the metallic inclusions. (credit Chiara Anzolini and Fabrizio Nestola)

When gem diamonds were polished and cut, expert diamond cutters often remove sections of the stones with inclusions. These offcut diamond pieces were not normally made available to scientists, and were usually considered waste, but the team made special efforts to get their hands on some.

“The project started with our collaborators at the GIA who have the opportunity to observe a number of large gem diamonds and have access to some of their offcut pieces,” said Shirey. “Evan Smith, a GIA postdoctoral researcher had a hypothesis that large diamonds could form deep in the mantle from metallic liquid, but we needed to the samples to figure it out.”

When they analyzed the offcuts, the team discovered multi-mineral metallic inclusions containing iron-nickel metal, an iron-carbide mineral known as cohenite, and the iron-sulfide mineral pyrrhotite. There were also traces of fluid methane and hydrogen in the thin space between the mineral phases and the encasing diamond. At the original pressure and temperature deep in Earth’s mantle, the composition of these multi-mineral inclusions suggested to the research team that a much larger mass of molten metallic liquid existed from which pure carbon crystallized to form diamonds. As each diamond grew, small droplets of the metallic liquid got trapped. As the diamonds were brought to Earth’s surface by volcanic eruption, the liquid droplets crystallized to the individual minerals.

“My motivation in this work was to solve this long-standing mystery about how these especially large and alluring diamonds form,” said Smith. “Everything about them suggests they form in a special way and that means they might tell us something new about the behavior of mantle carbon. In this research I was chasing an idea that I published a couple years ago, that the low nitrogen content and large size of these (CLIPPIR) diamonds might be linked to metallic iron in the mantle. I was thrilled when I started finding the first few inclusions. With the expertise of everyone involved we saw the observations unfold into an amazing story from the deep Earth.”

As well as diamonds with only the metal inclusions, the team found additional similar diamonds with silicate mineral inclusions –that coexisted with smaller amounts of metal. This assemblage suggests that all the metal-containing diamonds formed between 360 and 750km deep inside Earth. This was much deeper than most other gem diamonds, which form in the lower part of continental tectonic plates at depths of 150–200 km.

These two observations together show not only that Earth’s largest gemstone diamonds form extremely deep in the mantle, but also in regions of the mantle with metallic iron, the first time these aspects of the largest gem diamonds have been recognized.

“The idea of metallic iron in the silicate mantle at far shallower levels than Earth’s iron core , is something Earth scientists have expected for a while,” said Shirey. “A number of experiments and simulations predicted it, but now we have physical evidence that this is the case.”

Previous experiments and theory suggested for many years that small amounts of metallic iron existed in parts of the deep mantle below about 250 km depth. Though it’s still unclear how much metallic iron was present in the lower mantle, this was a key observation for understanding of Earth and the conditions under which it formed and evolved. Because the metallic liquid at these pressures and temperatures contains carbon and hydrogen it plays a hitherto undetected role in the geochemical cycles of these elements in the deep mantle.

“This result provides a direct link between diamond formation and deep mantle conditions, addressing a key goal of the Deep Carbon Observatory,” said DCO Executive Director Robert Hazen (Carnegie Institution for Science, USA). “The fact that it was made possible by a hugely successful collaboration between Diamonds and Mantle Geodynamics of Carbon group and the Gemological Institute of America was also very exciting, highlighting the importance of academic connections with industry and their important role in providing postdoctoral funding and the key specimens for this research.”

The 15 November 2016 edition of the journal Lithos delves into the role of natural diamonds in deep Earth research.

Titled “The nature of diamonds and their use in Earth’s study,” the 15 November 2016 edition of the journal Lithos delves into the role of natural diamonds in deep Earth research. This special issue was edited by DCO scientists involved the Reservoirs and Fluxes initiative, Diamonds and the Mantle Geodynamics of Carbon (DMGC).

This special issue of Lithos was compiled in recognition of the second International Diamond School, which took place in January 2015 in Bressanone, Italy. The Deep Carbon Observatory and the Gemological Institute of America sponsored the school, which brought together more than 80 graduate students and postdocs from around the world. Many of the students of the school are authors in the special issue.

Fabrizio Nestola (Università degli Studi di Padova, Italy), Matteo Alvaro (Università degli Studi di Pavia, Italy), Graham Pearson (University of Alberta, Canada), and Steven Shirey (Carnegie Institution for Science, USA) edited a selection of 30 original research articles from 134 authors for the issue. The papers cover four main research areas: geochemistry, diamond forming fluids, and diamond origin sources; geothermo-barometry and geochronology of diamonds; super-deep diamonds, carbonado-like diamonds and diamondites; and innovative methods for the investigation of diamonds.

 

CONTENTS

The Third International Diamond School took place at the University of Alberta, with the Deep Carbon Observatory as the main event sponsor (together with De Beers and IsoMass).

The Third International Diamond School took place at the University of Alberta, with the Deep Carbon Observatory as the main event sponsor (together with De Beers and IsoMass). DCO’s Graham Pearson (Reservoirs and Fluxes Scientific Steering Committee member; University of Alberta, Canada), Steve Shirey (Carnegie Institution for Science Department of Terrestrial Magnetism, USA), Thomas Stachel University of Alberta, Canada), Bob Luth (University of Alberta) and Fabrizio Nestola (University of Padua, Italy) were the principal conveners. The event continued in the tradition of having a mixed participation of students, senior academics, and industry. Seventy-five delegates, including 2 BSc students, and 30 Ph.D and Masters students from Canada, USA, Australia, and the UK attended, along with 18 delegates from industry and Government/Provincial Geological Surveys.

Prior to the conference 21 people (a mix of academics and students) attended a 2 day field trip to the Northwest Territories diamond mines and to see Archean geology around Yellowknife. The field trips were made possible by the generosity of Dominion Diamonds and Rio Tinto (Diavik Diamond Mine), as well as the staff of the Northwest Territories Geological Survey.

The scientific program consisted of 34 presentations, including 12 student talks, and 4 student posters that spanned a range of topics from the fundamentals of diamond formation through new mantle thermometry methods to aspects of diamond exploration and deposit evaluation. DCO early career scientists (non-students) who presented or attended included Emilie Thomassot (Nancy, France), Yakov Weiss (Columbia, USA) and Andrea Guiliani (Melbourne, Australia). The science program was supplemented by laboratory facility tours at the University of Alberta.