Lecture 13: Melting the Mantle and Volcano Types

Mantle plumes aren't pure primitive mantle; they're a blend of peridotitic mantle material and recycled crustal components (like subducted sediments and altered oceanic crust).

When combining two substances (e.g., seawater and freshwater), the sum of their mass fractions equals 1.

If you know the mass fraction of one substance (FA), you can calculate the mass fraction of the other (FB) by subtracting FA from 1 (FB = 1 - FA).

The salt content in a mixture of seawater and freshwater is directly proportional to the mass fraction of seawater.

The concentration of strontium (Sr) in a mixture of seawater and freshwater depends on the amount of each component and their initial strontium concentrations.

Chemical models and tracer studies quantify the movement of elements through the ocean's reservoirs.

In stable systems, the total input of an element equals the total output, plus any change in storage.

Elements whose storage change is negligible over long time scales.

Ore deposits containing sulfide minerals formed at mid-ocean ridges or other active tectonic areas from chemical reactions between hot magma and seawater.

Mineral structures formed from the precipitation of metal sulfides as hot mineral-rich water mixes with cooler ocean water.

The rate of seawater circulation through hydrothermal vents.

The movement of chemicals through rivers.

The hydrothermal vent flux is significantly less than the river flux (about 0.1%).

A ratio of two isotopes of strontium, used to determine the origin, processes affecting, and age of rocks, minerals, and fluids.

Geological processes related to the movement of oceanic plates under continental plates, leading to the recycling of crustal material.

The process of combining materials with different isotopic compositions to form a mixture. The resulting composition reflects the relative proportions of the original materials.

Mixing of two distinct components. In a plot of 87Sr/86Sr vs 1/Sr, the graph shows a linear trend, signifying two-component interaction in a fluid system.

The process where an unstable atomic nucleus transforms into a more stable nucleus, accompanied by the emission of radiation. Used in dating rocks and tracing materials.

The process by which the Earth's mantle and crust evolve and change over time, resulting in different compositions and isotopic ratios.

Suggests interaction with marine fluids or seawater, affecting the isotopic ratios of rocks and minerals involved.

Using the 87Sr/86Sr ratio in conjunction with 87Rb to determine the age of a rock or mineral.