Mantle 3He and CO2 degassing in carbonic and geothermal springs of Colorado and implications for neotectonics of the Rocky Mountains

Karl E. Karlstrom, Laura J. Crossey, David R. Hilton, and Peter H. Barry

Introduction• What is the topic of this paper? What are they saying that is new?

Introduction• What is the topic of this paper? What are they saying that is new?

“This paper shows that hot springs, carbonic springs, and CO2 regional gas fields can be surface vent regions for degassing of mantle volatiles in continental regions that are undergoing lithospheric extension and epeirogenic uplift.”

Helium-3 vs Helium-4• Helium-3 is a primordial substance in the

Earth's mantle, considered to have become entrapped within the Earth during planetary formation.

Helium-3 vs Helium-4• Helium-3 is a primordial substance in the

Earth's mantle, considered to have become entrapped within the Earth during planetary formation.

• Helium-4 is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth

Figure 1• What information

is the data attempting to convey?

Figure 1• What information

is the data attempting to convey?

• What is Rc/Ra?

Figure 1• What information

is the data attempting to convey?

• What is Rc/Ra?

• What does “Air Corrected” mean?

Figure 1• What information

is the data attempting to convey?

• What is Rc/Ra?

• What does “Air Corrected” mean?

• How do we measure helium ratios?

Figure 2• What is this plot

trying to say?

Modeling Sources of CO2

Sources that contribute to the CO2 load of springs include: (1) dissolution of carbonates (Ccarb), for example from Paleozoic carbonates along flow paths; (2) carbon of organic origin (Corg), including soil gas; and (3) deeply sourced (endogenic) CO2 (Cendo).

• What method is used to derive from which source the CO2 came from?

Figure 3

Figure 4• What are the

trends being illustrated?

CO2 Flux through Springs

• 109 moles/yr =44 million kg per year• Almost the weight of the Titanic, per year

CO2 Flux through Springs

• 109 moles/yr =44 million kg per year• Almost the weight of the Titanic, per year!

• 1011 moles/year • Amount of mass converted to energy by the sun in 1 sec.

CO2 Flux through Springs

• 109 moles/yr =44 million kg per year• Almost the weight of the Titanic, per year!

• 1011 moles/year • ~ amount of mass converted to energy by the sun in 1 sec.

• 1012 moles/year• ~10 X the mass of all humans alive!

Conclusions• Anything else?