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Jie (Jackie) Li

Professor

Ph.D. Harvard University   

B.S. USTC

 

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I am a geochemist and mineral physicist interested in understanding the response of material properties to extreme conditions and exploring the implications for the formation of habitable worlds.

 

Our studies have provided new insights into the composition, thermal state, and dynamics of rocky planets and moons, helping to solve a number of Earth Enigmas, Core Conundrums, Mantle Mysteries, and Planet Puzzles.

 

EARTH ENIGMAS

Synthesis Across Disciplines

 

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Phase transformations and chemical reactions drive planetary differentiation and element cycles. What are the key reactions governing the formation and evolution of the living Earth? Through a Sloan Foundation - Deep Carbon Observatory grant, I led a synthesis project “Earth in Five Reactions” to study how reactions control the movement of life’s ingredients in Earth. We held a multi-disciplinary international workshop in Washington DC in 2018, and published a special issue in American Mineralogists.

 

Understanding Earth’s inner workings requires synthesis of geochemistry and mineral physics with seismology and geodynamics. I have actively participated in CIDER (Cooperative Institute for Dynamic Earth Research) for more than one decade, giving lectures, organizing mini-symposiums, and serving as the Chair of its Advisory Committee.

 

Our cross-disciplinary projects have produced unique insights into big-picture questions.

“Deep carbon cycle through five reactions” AM 2019

“How did early Earth become our modern world?” ANEPS 2012

“Upside-down differentiation and Generation of a “primordial” lower mantle” Nature 2010

“Precipitation of multiple light elements to power Earth’s early dynamo” EPSL 2020

 

CORE CONUNDRUMS

Iron-Alloys at Extreme Conditions

 

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Earth’s core spans more than half of the planet’s radius, hosts most of its precious metals, and generates the geomagnetic field. How did the core form and what light elements kept the core molten and convecting? To answer these questions we simulate the conditions of proto- and present core in laboratory using large-volume press and diamond anvil cells, and then quantify the effects of high pressure and high temperature on the physical properties and chemical behavior of iron-rich alloys using microanalytical techniques and synchrotron X-ray diffraction and spectroscopy methods.

 

Our experimental investigations were supported by NSF grants and have provided constraints on the formation and composition of Earth’s core.

“Hidden carbon in Earth's inner core revealed by shear softening in dense Fe7C3 PNAS, 2014

Experimental constraints on core composition” TGC, 2014

“Element partitioning constraints on the light element composition of the Earth's core” GRL 2001

“Geochemistry of mantle-core differentiation at high pressure” NATURE 1996

 

MANTLE MYSTERIES

Compressed Silicates and Carbonates

 

 

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Seismic images revealed low-velocity regions above the Earth’s core-mantle boundary, including small patches of ultra-low velocity zone (ULVZ) and large low shear velocity provinces (LLSVP). What are the origins of these structures? Through high-pressure experiments using diamond anvil cells and synchrotron radiation, we probed the melting behavior, spin crossover, and densities of iron-bearing metals and silicates to help elucidate the nature of mantle heterogeneity.

Formation of large low shear velocity provinces through disproportionation of oxidized mantle” Nature Comm, In press

“Valence and spin states of iron are invisible in Earth’s lower mantle” Nature Comm, 2018

Origin of ultra-low velocity zones through mantle-derived metallic melt PNAS 2016

 

The Earth’s mantle transition zone (MTZ) is particularly interesting because it can hold the entire ocean’s water in crystalline structures and may pose barrier to diamond formation and carbon subduction. We performed experiments to test the intriguing hypothesis of hidden ocean in the MTZ, examine the stability of carbonates, and investigate the kinetics of diamond-forming reactions. Our observations have shed light on the nature and dynamics of the MTZ.

Metallic iron limits silicate hydration in Earth's transition zone” PNAS 2019

Determination of calcium carbonate and sodium carbonate melting curves up to Earth's transition zone pressures with implications for the deep carbon cycle” EPSL 2017

“Kinetic control on the provenance of superdeep diamonds” GRL 2019

 

PLANET PUZZLES

Geo-Cosmo-Astro

 

 

 

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The Earth’s magnetic field protects life from solar wind and cosmic rays. Today active fields are rare among rocky planets and only detected on Earth, Mercury and Ganymede. Through NASA support, we have conducted experiments to study the freezing of iron-alloys under high pressures. Our findings contributed new insights into the origin of planetary dynamo in iron-rich cores.

Non-ideal liquidus curve in the Fe-S system and Mercury's snowing core” GRL 2008

Thermal state and solidification regime of the Martian core: Insights from the melting behavior of FeNi-S at 20 GPa” EPSL 2020

“State and solidification of lunar core from melting experiments on Fe-Ni-S system” EPSL 2020

 

Earth was born out of the same parent nebula as other planets in the solar system, yet it is only known habitable planet today. What determines the path of chemical differentiation and thermal evolution for an Earth-like planet? Will we find another home for humans elsewhere? Through an NSF INSPIRE grant, I worked in a geo-cosmo-astro team to track Life’s Ingredients from outer space to inner core. We have uncovered important clues to the formation of habitable worlds.

Earth's carbon deficit caused by early loss through irreversible sublimation” Science Adv. In press

“Ingredients for a habitable Earth: Tracing C/N ratios from interstellar space through planet formation” PNAS 2015