Dhofar 008 L3.3

In thin section under the microscope it is easy to see that the components of Dhofar 008 L3.3 underwent several episodes of processing before their final assembly and delivery to earth. We see it in layered features and in the presence of enveloping compound chondrules.

Enveloping compound chondrules have one or more chondrules completely enclosed in another.
With enveloping compound chondrules the enclosed chondrules obviously had to form before the chondrule into which it became incorporated.

In another class of compound chondrules adhering chondrules became attached when molten or still-plastic chondrules impacted and stuck to already solid chondrules.

Sibling Compound Chondrules are adhering chondrules with similar textures and compositions.

Independent Compound Chondrules are adhering chondrules with different textures and compositions.

Returning to enveloping chondrules, if the interior and the enclosing chondrules are of the same type it can be difficult to discern the existence of the compound situation. Fortunately here we have barred olivine (BO) chondrules in porphyritic olivine pyroxene (POP) chondrules. The textural differences stand out. Further, BO chondrules are often single skeletal crystals that go to optical extinction all at once. This, too, highlights their presence in POP chondrules when the polarizing filters are rotated.

A BO chondrule, upper left, is enveloped in a large chondrule. There is a fragment of a radial pyroxene chondrule attached on the right. Dhofar 008 L3.3, thin section in cross-polarized light.

Here the BO chondrule is nearly in optical extinction.

A close-up of the BO chondrule.

A close-up with the BO chondrule in extinction – except for some recrystallized material interstitial to the olivine bars.

At the edge of the specimen, a BO chondrule enveloped by a POP chondrule. Dhofar 008 L3.3, thin section in cross-polarized light.

With the BO chondrule in extinction.

Appearing blue, a BO chondrule within and making up the bulk of a POP chondrule. Dhofar 008 L3.3, thin section in cross-polarized light.

The BO chondrule shows up best when in optical extinction.

Sibling compound barred olivine chondrules in Dhofar 008 L3.3. Thin section in cross-polarized light.

A small assemblage of mineral grains surrounded by very fine mineral grains all enclosed in a dust blanket. Dhofar 008 L3.3, thin section in cross-polarized light.

Several episodes of accretion and heating formed this beautifully layered feature. Dhofar 008 L3.3, thin section in cross-polarized light.

About the Author

John Kashuba
John is a natural history enthusiast living in Oregon.
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