<p>There may be something here that answers your question....</p>
<p><a href="https://www.researchgate.net/publication/237172123_The_Sept_Iles_anorthosite_complex_Field_relationships_geochronology_and_petrology" rel="nofollow noreferrer">https://www.researchgate.net/publication/237172123_The_Sept_Iles_anorthosite_complex_Field_relationships_geochronology_and_petrology</a></p>
<p>Its summary reads:</p>
<blockquote>
<p>The Sept Iles anorthosite complex is located in the Grenville (structural) Province of the Canadian Shield. Geochronological studies of both the basic and acidic portions of the complex show that it was intruded approximately 540 Ma ago and thus post-dates the Grenville orogeny by at least 500 Ma. Field relationships confirm the contemporaneity of the basic (anorthosite and gabbro) and acidic (syenite and granite) rocks. Differentiation of the basic magma was controlled by preferential nucleation in the boundary layer. Crystal separation due to gravity and possibly liquid immiscibility caused differentiation once intermediate or acidic magma compositions were formed. There is no evidence that crustal contamination has played a role in the generation of the acidic rocks. The complex has been intruded along the St. Lawrence graben fault, known to have been active at this time from the profusion of igneous rocks elsewhere along this structure, which are contemporaneous with the Sept Iles complex. Activity on this fault has disrupted the complex so that rocks found on the mainland were originally formed at the base of the complex, whereas rocks exposed on the islands were formed at the top of the complex. This study of the Sept Iles complex shows that anorthosite is not restricted to Precambrian terranes, and may be associated with acidic alkaline rocks and large-scale ensialic rifting.</p>
</blockquote>

CC BY-SA 4.0
2024-12-04T12:58:35.450Z
Could you please include a small summary of the paper? Link-only answers are often frown upon because links tend to rot.
Jean-Marie Prival
CC BY-SA 4.0
2024-12-05T13:06:39.840Z
I can try, although I have no knowledge of the subject - just found a paper that seemed to cover what the question was asking !
Simon Bates
CC BY-SA 4.0
2024-12-04T10:38:08.417Z
2024-12-09T09:14:49.277Z
2024-12-09T09:14:49.277Z
Simon Bates
<p>I was exploring some islands by boat recently and I came upon some pretty impressive rock formation. I'm interested in finding what mechanism produces those angle mineral strips. Some of them were a couple inches wide, others some feet wide. They were angled at around 45 degrees creating lines all across the side of the island. (Which was 25 to 30m high) <a href="https://i.sstatic.net/LsHMw.jpg" rel="noreferrer"><img src="https://i.sstatic.net/LsHMw.jpg" alt="The strip on the left of the image" /></a> I tried doing a research on Google but being unfamiliar with the terms of geology, I couldn't orient my search properly. Does anybody could point me to some articles or terms to help me research the subject or provide a quick explanation as to what causes those minerals to be aligned at those angles?<a href="https://i.sstatic.net/0WAPb.jpg" rel="noreferrer"><img src="https://i.sstatic.net/0WAPb.jpg" alt="enter image description here" /></a></p>
<p>The pictures aren't the best but you can see on the left of the first one the mineral strip and a smaller one on the second picture.</p>
<p>Thanks in advance!</p>

CC BY-SA 4.0
2023-02-28T09:00:00.013Z
Could you provide some information about the location? It would help to know the geological setting. It could be [veins](https://en.wikipedia.org/wiki/Vein_(geology)) or it could be [dikes](https://en.wikipedia.org/wiki/Dike_(geology)).
Jean-Marie Prival
CC BY-SA 4.0
2023-02-28T11:34:07.497Z
This is the island:
https://maps.app.goo.gl/NaSYTSuBFgUKqu8C9
Nathaniel
<geology><mineralogy><minerals>
What explains the angled stripes of mineral visible on the side of some islands?
Nathaniel
# What explains the angled stripes of mineral visible on the side of some islands?

(Asked by: username_0 on 2023-02-28)

I was exploring some islands by boat recently and I came upon some pretty impressive rock formation. I'm interested in finding what mechanism produces those angle mineral strips. Some of them were a couple inches wide, others some feet wide. They were angled at around 45 degrees creating lines all across the side of the island. (Which was 25 to 30m high) [![The strip on the left of the image](https://i.sstatic.net/LsHMw.jpg)](https://i.sstatic.net/LsHMw.jpg) I tried doing a research on Google but being unfamiliar with the terms of geology, I couldn't orient my search properly. Does anybody could point me to some articles or terms to help me research the subject or provide a quick explanation as to what causes those minerals to be aligned at those angles?[![enter image description here](https://i.sstatic.net/0WAPb.jpg)](https://i.sstatic.net/0WAPb.jpg)

The pictures aren't the best but you can see on the left of the first one the mineral strip and a smaller one on the second picture.

Thanks in advance!

**Tags:** geology, mineralogy, minerals

> **Comments:**
> **username_1**: Could you provide some information about the location? It would help to know the geological setting. It could be [veins](https://en.wikipedia.org/wiki/Vein_(geology)) or it could be [dikes](https://en.wikipedia.org/wiki/Dike_(geology)).  
> **username_0**: This is the island: https://maps.app.goo.gl/NaSYTSuBFgUKqu8C9  

---

## 1 answers

### Answer by username_2 on 2024-12-04. Score: 0

There may be something here that answers your question....

<https://www.researchgate.net/publication/237172123_The_Sept_Iles_anorthosite_complex_Field_relationships_geochronology_and_petrology>

Its summary reads:

> The Sept Iles anorthosite complex is located in the Grenville (structural) Province of the Canadian Shield. Geochronological studies of both the basic and acidic portions of the complex show that it was intruded approximately 540 Ma ago and thus post-dates the Grenville orogeny by at least 500 Ma. Field relationships confirm the contemporaneity of the basic (anorthosite and gabbro) and acidic (syenite and granite) rocks. Differentiation of the basic magma was controlled by preferential nucleation in the boundary layer. Crystal separation due to gravity and possibly liquid immiscibility caused differentiation once intermediate or acidic magma compositions were formed. There is no evidence that crustal contamination has played a role in the generation of the acidic rocks. The complex has been intruded along the St. Lawrence graben fault, known to have been active at this time from the profusion of igneous rocks elsewhere along this structure, which are contemporaneous with the Sept Iles complex. Activity on this fault has disrupted the complex so that rocks found on the mainland were originally formed at the base of the complex, whereas rocks exposed on the islands were formed at the top of the complex. This study of the Sept Iles complex shows that anorthosite is not restricted to Precambrian terranes, and may be associated with acidic alkaline rocks and large-scale ensialic rifting.

> **Comments:**
> **username_1**: Could you please include a small summary of the paper? Link-only answers are often frown upon because links tend to rot.  
> **username_2**: I can try, although I have no knowledge of the subject - just found a paper that seemed to cover what the question was asking !  

---

