I am studying for the NY state regents and am so confused; What is the difference between banding and mineral allignment in metamorphic rocks. Thank you so much :)
2007-06-16 06:32:28 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Earth Sciences & Geology
ps what makes stromatolites signifigant in Earth's timelime, or rather, what seperates the precambrian and phanerozoic eons.
2007-06-16 06:40:16 · update #1
no, I don't mean foliated. metamorphic rocks are either foliated or non foliated, then foliated rocks are clasified as having mineral allignment or banding. I want to know what banding and mineral allignment are.
2007-06-16 06:42:34 · update #2
Banding and mineral alignment are two possible type of fabric in metamorphic rocks.
Banding means that there are discrete bands (or layers) of different minerals in a rock. For example, in a gneiss, you could have alternating layers of quartz, micas, and amphibole. The minerals in each layer may or may not be aligned.
An alignment (not allignment - check your spelling!) of minerals means that one of the crystal axes of minerals is aligned with other minerals. For example, in a biotite schist, more than 50% of the biotite crystals would be aligned parrallel with each other, but not necessarily banded. The amount of alignment can be called schistosity.
Banding and alignment are types of foliation, and are the key criteria used to distinguish between a gneiss and a schist. A gneiss, which is banded, will have more or less discrete layers each dominated by a specific mineral, while a schist will be mineralogically homogenous, but the mineral grains or prisms will be aligned. There's lots of schist and gneiss in NY, so just look at the two kinds of rock and it should be obvious!
A rock with both mineral alignment and banding could be called a gneissic schist or a schistose gneiss, depending on which is dominant. The orientation and amount of gneissosity and schistosity can be measured to help determine the amount and type of deformation that a rock has suffered.
Hope that helps!
2007-06-16 06:57:48 · answer #1 · answered by minefinder 7 · 0⤊ 0⤋
Banding Metamorphic Rocks
2016-11-01 22:18:49 · answer #2 · answered by Anonymous · 0⤊ 0⤋
My initial thought was (2) (one is formed hot, the other not), but a lot of time the shale deposited on top of the basalt, so there would be no contact metamorphism expected (the basalt was already cool). So instead, I would say (3), because both basalt and granite form at high temperatures, and no matter which formed first, the other would be hot relative to the first one that was put into place, and thus would cause a zone of contact (thermal) metamorphism in the earlier rock. 1 and 4 are clearly not the answer.
2016-05-17 09:20:49 · answer #3 · answered by Anonymous · 0⤊ 0⤋
heyt im taking it too. High five. lol. banding is mineral alignment except in banding the minerals are not alligned straight. in banding they are aligned in a scribbly way. like mountains. in mineral allignment, they (minerals) line up straight.
2007-06-16 06:47:02 · answer #4 · answered by ♥ F@$H!0N ♥ 5 · 1⤊ 0⤋
Do you mean foliated?
2007-06-16 06:39:41 · answer #5 · answered by Liz P 2 · 0⤊ 0⤋